code:
\input texinfo.tex    @c -*-texinfo-*-
@c $Id$

@c Everything between the start/end of header lines will be passed by
@c Emacs's {texinfo,makeinfo}-format region commands.  See the `start of
@c header' node for more info.
@c %**start of header

@c Automake requires this
@setfilename texinfo.info

@c Automake automatically updates version.texi to @set VERSION and
@c @set UPDATED to appropriate values.
@include version.texi
@settitle GNU Texinfo @value{VERSION}

@c Define a new index for command-line options.
@defcodeindex op

@c Put everything except function (command, in this case) names in one
@c index (arbitrarily chosen to be the concept index).
@syncodeindex op cp
@syncodeindex vr cp
@syncodeindex pg cp

@tex
\global\usebracesinindexestrue
@end tex

@c finalout

@comment %**end of header

@copying
This manual is for GNU Texinfo (version @value{VERSION}, @value{UPDATED}),
a documentation system that can produce both online information and a
printed manual from a single source using semantic markup.

Copyright @copyright{} 1988, 1990, 1991, 1992, 1993, 1995, 1996, 1997,
1998, 1999, 2001, 2001, 2003, 2004, 2005, 2006, 2007, 2008, 2009,
2010, 2011, 2012, 2013, 2014, 2015, 2016 Free Software Foundation, Inc.

@quotation
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3 or
any later version published by the Free Software Foundation; with no
Invariant Sections, with the Front-Cover Texts being ``A GNU Manual'',
and with the Back-Cover Texts as in (a) below.  A copy of the license
is included in the section entitled ``GNU Free Documentation
License''.

(a) The FSF's Back-Cover Text is: ``You have the freedom to copy and
modify this GNU manual.  Buying copies from the FSF supports it in
developing GNU and promoting software freedom.''
@end quotation
@end copying

@dircategory Texinfo documentation system
@direntry
* Texinfo: (texinfo).           The GNU documentation format.
* install-info: (texinfo)Invoking install-info. Update info/dir entries.
* makeinfo: (texinfo)Invoking makeinfo.         Translate Texinfo source.
* pod2texi: (pod2texi)Invoking pod2texi.        Translate Perl POD to Texinfo.
* texi2dvi: (texinfo)Format with texi2dvi.      Print Texinfo documents.
* texi2pdf: (texinfo)PDF Output.                PDF output for Texinfo.
* pdftexi2dvi: (texinfo)PDF Output.             PDF output for Texinfo.
* texindex: (texinfo)Format with tex/texindex.  Sort Texinfo index files.
@end direntry

@c Set smallbook if printing in smallbook format so the example of the
@c smallbook font is actually written using smallbook; in bigbook, a kludge
@c is used for TeX output.  Do this through the -t option to texi2dvi,
@c so this same source can be used for other paper sizes as well.
@c smallbook
@c set smallbook
@c @@clear smallbook

@c If you like blank pages, add through texi2dvi -t.
@c setchapternewpage odd

@set txiindexatsignignore
@set txiindexbackslashignore
@set txiindexlessthanignore
@set txiindexhyphenignore

@titlepage
@title Texinfo
@subtitle The GNU Documentation Format
@subtitle for Texinfo version @value{VERSION}, @value{UPDATED}

@author Robert J. Chassell
@author Richard M. Stallman

@c Include the Distribution inside the titlepage so
@c that headings are turned off.

@page
@vskip 0pt plus 1filll
@insertcopying

@sp 1
Published by the Free Software Foundation @*
51 Franklin St, Fifth Floor @*
Boston, MA 02110-1301 @*
USA @*
ISBN 1-882114-67-1 @c for version 4.0, September 1999.
@c ISBN 1-882114-65-5 is for version 3.12, March 1998.
@c ISBN 1-882114-64-7 is for edition 2.24 of November 1996.
@c ISBN 1-882114-63-9 is for edition 2.20 of 28 February 1995.

@sp 1
Cover art by Etienne Suvasa.
@end titlepage

@summarycontents
@contents

@ifnottex
@node Top
@top Texinfo

This manual is for GNU Texinfo (version @value{VERSION}, @value{UPDATED}),
a documentation system that can produce both online information and a
printed manual from a single source using semantic markup.

The first part of this master menu lists the major nodes in this Info
document, including the @@-command and concept indices.  The rest of
the menu lists all the lower-level nodes in the document.
@end ifnottex

@menu
* Copying Conditions::          Your rights.
* Overview::                    Texinfo in brief.
* Writing a Texinfo File::      Format of a Texinfo source file.
* Beginning and Ending a File:: Beginning and end of a Texinfo file.
* Nodes::                       Writing nodes, the basic unit of Texinfo.
* Chapter Structuring::         Creating chapters, sections, appendices, etc.
* Cross References::            Writing cross-references.
* Marking Text::                Marking words and phrases as code,
                                    keyboard input, meta-syntactic
                                    variables, and the like.
* Quotations and Examples::     Block quotations, examples, etc.
* Lists and Tables::            Itemized or numbered lists, and tables.
* Special Displays::            Floating figures and footnotes.
* Indices::                     Creating indices.
* Insertions::                  Inserting @@-signs, braces, etc.
* Breaks::                      Forcing or preventing line and page breaks.
* Definition Commands::         Describing functions and the like uniformly.
* Internationalization::        Supporting languages other than English.
* Conditionals::                Specifying text for only some output cases.
* Defining New Texinfo Commands:: User-defined macros and aliases.
* Include Files::               How to incorporate other Texinfo files.
* Hardcopy::                    Output for paper, with @TeX{}.
* Generic Translator @command{texi2any}:: @command{texi2any}, an all-purpose converter.
* Creating and Installing Info Files:: Details on Info output.
* Generating HTML::             Details on HTML output.
@c * texi2any Output Customization:: Fine tuning with initialization files.

Appendices

* @@-Command Details::           Details of the Texinfo @@-commands.
* Tips::                        Hints on how to write a Texinfo document.
* Sample Texinfo Files::        Complete examples, including full texts.
* Texinfo Mode::                Using the GNU Emacs Texinfo mode.
* Headings::                    How to write page headings and footings.
* Catching Mistakes::           How to find mistakes in formatting.
* Info Format Specification::   Technical details of the Info file format.
* GNU Free Documentation License:: Copying this manual.
* Command and Variable Index::  A menu containing commands and variables.
* General Index::               A menu covering many topics.

@detailmenu
 --- The Detailed Node Listing ---

Overview of Texinfo

* Reporting Bugs::              Submitting effective bug reports.
* Output Formats::              Overview of the supported output formats.
* Info Files::                  What is an Info file?
* Printed Books::               Characteristics of a printed book or manual.
* Adding Output Formats::       Man pages and implementing new formats.
* History::                     Acknowledgements, contributors and genesis.

Writing a Texinfo File

* Command Syntax::              @@-commands are used for formatting.
* Conventions::                 General rules for writing a Texinfo file.
* Comments::                    Writing comments and ignored text in general.
* Minimum::                     What a Texinfo file must have.
* Short Sample::                A short sample Texinfo file.

Beginning and Ending a Texinfo File

* Sample Beginning::            A sample beginning for a Texinfo file.
* Texinfo File Header::         The first lines.
* Document Permissions::        Ensuring your manual is free.
* Titlepage & Copyright Page::  Creating the title and copyright pages.
* Contents::                    How to create a table of contents.
* The Top Node::                Creating the `Top' node and master menu.
* Global Document Commands::    Affecting formatting throughout.
* Ending a File::               What is at the end of a Texinfo file?

Texinfo File Header

* First Line::                  The first line of a Texinfo file.
* Start of Header::             Formatting a region requires this.
* @code{@@setfilename}::                Tell Info the name of the Info file.
* @code{@@settitle}::                   Create a title for the printed work.
* End of Header::               Formatting a region requires this.

Document Permissions

* @code{@@copying}::                    Declare the document's copying permissions.
* @code{@@insertcopying}::              Where to insert the permissions.

Title and Copyright Pages

* @code{@@titlepage}::                  Create a title for the printed document.
* @code{@@titlefont @@center @@sp}::      The @code{@@titlefont}, @code{@@center},
                                 and @code{@@sp} commands.
* @code{@@title @@subtitle @@author}::    The @code{@@title}, @code{@@subtitle},
                                 and @code{@@author} commands.
* Copyright::                   How to write the copyright notice and
                                 include copying permissions.
* Heading Generation::          Turn on page headings after the title and
                                 copyright pages.

The `Top' Node and Master Menu

* Top Node Example::
* Master Menu Parts::

Global Document Commands

* @code{@@documentdescription}::        Document summary for the HTML output.
* @code{@@setchapternewpage}::          Start chapters on right-hand pages.
* @code{@@headings}::                   An option for turning headings on and off
                                        and double or single sided printing.
* @code{@@paragraphindent}::            Specify paragraph indentation.
* @code{@@firstparagraphindent}::       Suppressing first paragraph indentation.
* @code{@@exampleindent}::              Specify environment indentation.

Nodes

* Texinfo Document Structure::  How Texinfo manuals are usually arranged.
* Node Names::                  How to choose node names.
* Writing a Node::              How to write an @code{@@node} line.
* Node Line Requirements::      Keep names unique.
* First Node::                  How to write a `Top' node.
* @code{@@top} Command::                How to use the @code{@@top} command.
* Node Menu Illustration::      A diagram, and sample nodes and menus.
* @command{makeinfo} Pointer Creation::   Letting makeinfo determine node pointers.
* Menus::                       Listing subordinate nodes.

Menus

* Writing a Menu::              What is a menu?
* Menu Example::                Two and three part menu entries.
* Menu Location::               Menus go at the ends of nodes.
* Menu Parts::                  A menu entry has three parts.
* Less Cluttered Menu Entry::   Two part menu entry.
* Other Info Files::            How to refer to a different Info file.

Chapter Structuring

* Tree Structuring::            A manual is like an upside down tree @dots{}
* Structuring Command Types::   How to divide a manual into parts.
* @code{@@chapter}::                    Chapter structuring.
* @code{@@unnumbered @@appendix}::
* @code{@@majorheading @@chapheading}::
* @code{@@section}::
* @code{@@unnumberedsec @@appendixsec @@heading}::
* @code{@@subsection}::
* @code{@@unnumberedsubsec @@appendixsubsec @@subheading}::
* @code{@@subsubsection}::              Commands for the lowest level sections.
* @code{@@part}::                       Collections of chapters.
* Raise/lower sections::        How to change commands' hierarchical level.

Cross-references

* References::                  What cross-references are for.
* Cross Reference Commands::    A summary of the different commands.
* Cross Reference Parts::       A cross-reference has several parts.
* @code{@@xref}::                       Begin a reference with `See' @dots{}
* Referring to a Manual as a Whole::   Refer to an entire manual.
* @code{@@ref}::                        A reference for the last part of a sentence.
* @code{@@pxref}::                      How to write a parenthetical cross-reference.
* @code{@@anchor}::                     Defining arbitrary cross-reference targets
* @code{@@inforef}::                    How to refer to an Info-only file.
* @code{@@url}::                        How to refer to a uniform resource locator.
* @code{@@cite}::                       How to refer to books not in the Info system.

@code{@@xref}

* One Argument::                @code{@@xref} with one argument.
* Two Arguments::               @code{@@xref} with two arguments.
* Three Arguments::             @code{@@xref} with three arguments.
* Four and Five Arguments::     @code{@@xref} with four and five arguments.

@code{@@url}, @code{@@uref@{@var{url}[, @var{text}][, @var{replacement}]@}}

* @code{@@url} Examples::           Examples of using all the forms of @code{@@url}.
* URL Line Breaking::       How lines are broken within @code{@@url} text.
* @code{@@url} PDF Output Format::  A special option to hide links in PDF output.
* PDF Colors::              Colorizing urls and other links in PDF output.

Marking Text, Words and Phrases

* Indicating::                  How to indicate definitions, files, etc.
* Emphasis::                    How to emphasize text.

Indicating Definitions, Commands, etc.

* Useful Highlighting::         Highlighting provides useful information.
* @code{@@code}::                       Indicating program code.
* @code{@@kbd}::                        Showing keyboard input.
* @code{@@key}::                        Specifying keys.
* @code{@@samp}::                       Indicating a literal sequence of characters.
* @code{@@verb}::                       Indicating a verbatim sequence of characters.
* @code{@@var}::                        Indicating metasyntactic variables.
* @code{@@env}::                        Indicating environment variables.
* @code{@@file}::                       Indicating file names.
* @code{@@command}::                    Indicating command names.
* @code{@@option}::                     Indicating option names.
* @code{@@dfn}::                        Specifying definitions.
* @code{@@abbr}::                       Indicating abbreviations.
* @code{@@acronym}::                    Indicating acronyms.
* @code{@@indicateurl}::                Indicating an example url.
* @code{@@email}::                      Indicating an electronic mail address.

Emphasizing Text

* @code{@@emph @@strong}::               How to emphasize text in Texinfo.
* Smallcaps::                   How to use the small caps font.
* Fonts::                       Various font commands for printed output.

Quotations and Examples

* Block Enclosing Commands::    Different constructs for different purposes.
* @code{@@quotation}::                  Writing a quotation.
* @code{@@indentedblock}::              Block of text indented on left.
* @code{@@example}::                    Writing an example in a fixed-width font.
* @code{@@verbatim}::                   Writing a verbatim example.
* @code{@@verbatiminclude}::            Including a file verbatim.
* @code{@@lisp}::                       Illustrating Lisp code.
* @code{@@small@dots{}}::                   Examples in a smaller font.
* @code{@@display}::                    Writing an example in the current font.
* @code{@@format}::                     Writing an example without narrowed margins.
* @code{@@exdent}::                     Undo indentation on a line.
* @code{@@flushleft @@flushright}::      Pushing text flush left or flush right.
* @code{@@raggedright}::                Avoiding justification on the right.
* @code{@@noindent}::                   Preventing paragraph indentation.
* @code{@@indent}::                     Forcing paragraph indentation.
* @code{@@cartouche}::                  Drawing rounded rectangles around text.

Lists and Tables

* Introducing Lists::           Texinfo formats lists for you.
* @code{@@itemize}::                    How to construct a simple list.
* @code{@@enumerate}::                  How to construct a numbered list.
* Two-column Tables::           How to construct a two-column table.
* Multi-column Tables::         How to construct generalized tables.

Making a Two-column Table

* @code{@@table}::                      How to construct a two-column table.
* @code{@@ftable @@vtable}::             Automatic indexing for two-column tables.
* @code{@@itemx}::                      How to put more entries in the first column.

@code{@@multitable}: Multi-column Tables

* Multitable Column Widths::    Defining multitable column widths.
* Multitable Rows::             Defining multitable rows, with examples.

Special Displays

* Floats::                      Figures, tables, and the like.
* Images::                      Including graphics and images.
* Footnotes::                   Writing footnotes.

Floats

* @code{@@float}::                      Producing floating material.
* @code{@@caption @@shortcaption}::      Specifying descriptions for floats.
* @code{@@listoffloats}::               A table of contents for floats.

Inserting Images

* Image Syntax::
* Image Scaling::

Footnotes

* Footnote Commands::           How to write a footnote in Texinfo.
* Footnote Styles::             Controlling how footnotes appear in Info.

Indices

* Index Entries::               Choose different words for index entries.
* Predefined Indices::          Use different indices for different kinds
                                 of entries.
* Indexing Commands::           How to make an index entry.
* Printing Indices & Menus::    How to print an index in hardcopy and
                                 generate index menus in Info.
* Combining Indices::           How to combine indices.
* New Indices::                 How to define your own indices.

Combining Indices

* @code{@@syncodeindex}::               How to merge two indices, using @code{@@code}
                                 font for the merged-from index.
* @code{@@synindex}::                   How to merge two indices, using the
                                 roman font for the merged-from index.

Special Insertions

* Special Characters::          Inserting @@ @{@} , \ #
* Inserting Quote Characters::  Inserting left and right quotes, in code.
* Inserting Space::             Inserting the right amount of whitespace.
* Inserting Accents::           Inserting accents and special characters.
* Inserting Quotation Marks::   Inserting quotation marks.
* Inserting Subscripts and Superscripts:: Inserting sub/superscripts.
* Inserting Math::              Formatting mathematical expressions.
* Glyphs for Text::             Inserting dots, bullets, currencies, etc.
* Glyphs for Programming::      Indicating results of evaluation,
                                 expansion of macros, errors, etc.
* Inserting Unicode::           Inserting a Unicode character by code point.

Special Characters: Inserting @@ @{@} , \ #

* Inserting an Atsign::         @code{@@@@}, @code{@@atchar@{@}}.
* Inserting Braces::            @code{@@@{ @@@}}, @code{@@l rbracechar@{@}}.
* Inserting a Comma::           , and @code{@@comma@{@}}.
* Inserting a Backslash::       \ and @code{@@backslashchar@{@}}.
* Inserting a Hashsign::        # and @code{@@hashchar@{@}}.

Inserting Space

* Multiple Spaces::             Inserting multiple spaces.
* Not Ending a Sentence::       Sometimes a . doesn't end a sentence.
* Ending a Sentence::           Sometimes it does.
* @code{@@frenchspacing}::              Specifying end-of-sentence spacing.
* @code{@@dmn}::                        Formatting a dimension.

Glyphs for Text

* @code{@@TeX @@LaTeX}::                 The @TeX{} logos.
* @code{@@copyright}::                  The copyright symbol (c in a circle).
* @code{@@registeredsymbol}::           The registered symbol (R in a circle).
* @code{@@dots}::                       How to insert ellipses: @dots{} and @enddots{}
* @code{@@bullet}::                     How to insert a bullet: @bullet{}
* @code{@@euro}::                       How to insert the euro currency symbol.
* @code{@@pounds}::                     How to insert the pounds currency symbol.
* @code{@@textdegree}::                 How to insert the degrees symbol.
* @code{@@minus}::                      How to insert a minus sign.
* @code{@@geq @@leq}::                   How to insert greater/less-than-or-equal signs.

Glyphs for Programming

* Glyphs Summary::
* @code{@@result}::                     How to show the result of expression.
* @code{@@expansion}::                  How to indicate an expansion.
* @code{@@print}::                      How to indicate generated output.
* @code{@@error}::                      How to indicate an error message.
* @code{@@equiv}::                      How to indicate equivalence.
* @code{@@point}::                      How to indicate the location of point.
* Click Sequences::             Inserting GUI usage sequences.

Forcing and Preventing Breaks

* Break Commands::              Summary of break-related commands.
* Line Breaks::                 Forcing line breaks.
* @code{@@- @@hyphenation}::             Helping @TeX{} with hyphenation points.
* @code{@@allowcodebreaks}::            Controlling line breaks within @@code text.
* @code{@@w}::                          Preventing unwanted line breaks in text.
* @code{@@tie}::                        Inserting an unbreakable but varying space.
* @code{@@sp}::                         Inserting blank lines.
* @code{@@page}::                       Forcing the start of a new page.
* @code{@@group}::                      Preventing unwanted page breaks.
* @code{@@need}::                       Another way to prevent unwanted page breaks.

Definition Commands

* Def Cmd Template::            Writing descriptions using definition commands.
* Def Cmd Continuation Lines::  Continuing the heading over source lines.
* Optional Arguments::          Handling optional and repeated arguments.
* @code{@@deffnx}::                     Group two or more `first' lines.
* Def Cmds in Detail::          Reference for all the definition commands.
* Def Cmd Conventions::         Conventions for writing definitions.
* Sample Function Definition::  An example.

The Definition Commands

* Functions Commands::          Commands for functions and similar entities.
* Variables Commands::          Commands for variables and similar entities.
* Typed Functions::             Commands for functions in typed languages.
* Typed Variables::             Commands for variables in typed languages.
* Data Types::                  The definition command for data types.
* Abstract Objects::            Commands for object-oriented programming.

Object-Oriented Programming

* Variables: Object-Oriented Variables.
* Methods:   Object-Oriented Methods.

Internationalization

* @code{@@documentlanguage}::           Declaring the current language.
* @code{@@documentencoding}::           Declaring the input encoding.

Conditionally Visible Text

* Conditional Commands::        Text for a given format.
* Conditional Not Commands::    Text for any format other than a given one.
* Raw Formatter Commands::      Using raw formatter commands.
* Inline Conditionals::         Brace-delimited conditional text.
* @code{@@set @@clear @@value}::          Variable tests and substitutions.
* Testing for Texinfo Commands:: Testing if a Texinfo command is available.
* Conditional Nesting::         Using conditionals inside conditionals.

Flags: @code{@@set}, @code{@@clear}, conditionals, and @code{@@value}

* @code{@@set @@value}::                 Expand a flag variable to a string.
* @code{@@ifset @@ifclear}::             Format a region if a flag is set.
* @code{@@inlineifset @@inlineifclear}:: Brace-delimited flag conditionals.
* @code{@@value} Example::              An easy way to update edition information.

Defining New Texinfo Commands

* Defining Macros::             Defining and undefining new commands.
* Invoking Macros::             Using a macro, once you've defined it.
* Macro Details::               Limitations of Texinfo macros.
* @code{@@alias}::                      Command aliases.
* @code{@@definfoenclose}::             Customized highlighting.
* External Macro Processors::   @code{#line} directives.

External Macro Processors: Line Directives

* @samp{#line} Directive::
* TeX: @samp{#line} and @TeX{}.
* Syntax: @samp{#line} Syntax Details.

Include Files

* Using Include Files::         How to use the @code{@@include} command.
* @code{texinfo-multiple-files-update}:: How to create and update nodes and
                                     menus when using included files.
* Include Files Requirements::  @code{texinfo-multiple-files-update} needs.
* Sample Include File::         A sample outer file with included files
                                     within it; and a sample included file.
* Include Files Evolution::     How use of the @code{@@include} command
                                     has changed over time.

Formatting and Printing Hardcopy

* Use @TeX{}::                     Use @TeX{} to format for hardcopy.
* Format with @command{texi2dvi}::        The simplest way to format.
* Format with @command{tex}/@command{texindex}::    Formatting with explicit shell commands.
* Print with @command{lpr}::              How to print.
* Within Emacs::                How to format and print from an Emacs shell.
* Texinfo Mode Printing::       How to format and print in Texinfo mode.
* Compile-Command::             How to print using Emacs's compile command.
* Requirements Summary::        @TeX{} formatting requirements summary.
* Preparing for @TeX{}::           What to do before you use @TeX{}.
* Overfull hboxes::             What are and what to do with overfull hboxes.
* @code{@@smallbook}::                  How to print small format books and manuals.
* A4 Paper::                    How to print on A4 or A5 paper.
* @code{@@pagesizes}::                  How to print with customized page sizes.
* Cropmarks and Magnification:: How to print marks to indicate the size
                                 of pages and how to print scaled up output.
* PDF Output::                  Portable Document Format output.
* Obtaining @TeX{}::               How to obtain @TeX{}.

Format with @command{tex}/@command{texindex}

* Formatting Partial Documents::
* Details of @command{texindex}::

@command{texi2any}: The Generic Translator for Texinfo

* Reference Implementation::    @command{texi2any}: the reference implementation.
* Invoking @command{texi2any}::           Running the translator from a shell.
* @command{texi2any} Environment Variables::
* @command{texi2any} Printed Output::     Calling @command{texi2dvi}.
* Pointer Validation::          How to check that pointers point somewhere.
* Customization Variables::     Configuring @command{texi2any}.
* Internationalization of Document Strings:: Translating program-inserted text.
* Invoking @command{pod2texi}::           Translating Perl pod to Texinfo.
* @command{texi2html}::                   An ancestor of @command{texi2any}.

Customization Variables

* Commands: Customization Variables for @@-Commands.
* Options:  Customization Variables and Options.
* HTML:     HTML Customization Variables.
* Other:    Other Customization Variables.

Creating and Installing Info Files

* Creating an Info File::
* Installing an Info File::

Creating an Info File

* @command{makeinfo} Advantages::         @command{makeinfo} provides better error checking.
* @code{makeinfo} in Emacs::           How to run @code{makeinfo} from Emacs.
* @code{texinfo-format} commands::     Two Info formatting commands written
                                 in Emacs Lisp are an alternative
                                 to @code{makeinfo}.
* Batch Formatting::            How to format for Info in Emacs batch mode.
* Tag and Split Files::         How tagged and split files help Info
                                 to run better.

Installing an Info File

* Directory File::              The top level menu for all Info files.
* New Info File::               Listing a new Info file.
* Other Info Directories::      How to specify Info files that are
                                 located in other directories.
* Installing Dir Entries::      How to specify what menu entry to add
                                 to the Info directory.
* Invoking @command{install-info}::       @code{install-info} options.

Generating HTML

* HTML Translation::       Details of the HTML output.
* HTML Splitting::         How HTML output is split.
* HTML CSS::               Influencing HTML output with Cascading Style Sheets.
* HTML Xref::              Cross-references in HTML output.

HTML Cross-references

* Link Basics:       HTML Xref Link Basics.
* Node Expansion:    HTML Xref Node Name Expansion.
* Command Expansion: HTML Xref Command Expansion.
* 8-bit Expansion:   HTML Xref 8-bit Character Expansion.
* Mismatch:          HTML Xref Mismatch.
* Configuration:     HTML Xref Configuration. htmlxref.cnf.
* Preserving links:  HTML Xref Link Preservation. MANUAL-noderename.cnf.

Sample Texinfo Files

* Short Sample Texinfo File::
* GNU Sample Texts::
* Verbatim Copying License::
* All-permissive Copying License::

Using Texinfo Mode

* Texinfo Mode Overview::       How Texinfo mode can help you.
* Emacs Editing::               Texinfo mode adds to GNU Emacs' general
                                  purpose editing features.
* Inserting::                   How to insert frequently used @@-commands.
* Showing the Structure::       How to show the structure of a file.
* Updating Nodes and Menus::    How to update or create new nodes and menus.
* Info Formatting::             How to format for Info.
* Printing::                    How to format and print part or all of a file.
* Texinfo Mode Summary::        Summary of all the Texinfo mode commands.

Updating Nodes and Menus

* Updating Commands::           Five major updating commands.
* Updating Requirements::       How to structure a Texinfo file for
                                  using the updating command.
* Other Updating Commands::     How to indent descriptions, insert
                                  missing nodes lines, and update
                                  nodes in sequence.

Page Headings

* Headings Introduced::         Conventions for using page headings.
* Heading Format::              Standard page heading formats.
* Heading Choice::              How to specify the type of page heading.
* Custom Headings::             How to create your own headings and footings.

Catching Mistakes

* @command{makeinfo} Preferred::          @code{makeinfo} finds errors.
* Debugging with Info::         How to catch errors with Info formatting.
* Debugging with @TeX{}::          How to catch errors with @TeX{} formatting.
* Using @code{texinfo-show-structure}:: How to use @code{texinfo-show-structure}.
* Using @code{occur}::                 How to list all lines containing a pattern.
* Running @code{Info-validate}::       How to find badly referenced nodes.

Finding Badly Referenced Nodes

* Using @code{Info-validate}::         How to run @code{Info-validate}.
* Unsplit::                     How to create an unsplit file.
* Tagifying::                   How to tagify a file.
* Splitting::                   How to split a file manually.

Info Format Specification

* General: Info Format General Layout.
* Text:    Info Format Text Constructs.

Info Format General Layout

* Whole:           Info Format Whole Manual. Split vs.@: nonsplit manuals.
* Preamble:        Info Format Preamble.
* Indirect:        Info Format Indirect Table.
* Tag table:       Info Format Tag Table.
* Local variables: Info Format Local Variables.
* Regular nodes:   Info Format Regular Nodes.

Info Format Text Constructs

* Info Format Menu::
* Info Format Image::
* Info Format Printindex::
* Info Format Cross Reference::

@end detailmenu
@end menu

@c Reward readers for getting to the end of the menu :).
@c Contributed by Arnold Robbins.
@quotation
Documentation is like sex: when it is good, it is very, very good; and
when it is bad, it is better than nothing.
---Dick Brandon
@end quotation

@node Copying Conditions
@unnumbered Texinfo Copying Conditions
@cindex Copying conditions
@cindex Conditions for copying Texinfo
@cindex Free software
@cindex Libre software

GNU Texinfo is @dfn{free software}; this means that everyone is free
to use it and free to redistribute it on certain conditions.  Texinfo
is not in the public domain; it is copyrighted and there are
restrictions on its distribution, but these restrictions are designed
to permit everything that a good cooperating citizen would want to do.
What is not allowed is to try to prevent others from further sharing
any version of Texinfo that they might get from you.

Specifically, we want to make sure that you have the right to give away
copies of the programs that relate to Texinfo, that you receive source
code or else can get it if you want it, that you can change these
programs or use pieces of them in new free programs, and that you know
you can do these things.

To make sure that everyone has such rights, we have to forbid you to
deprive anyone else of these rights.  For example, if you distribute
copies of the Texinfo related programs, you must give the recipients all
the rights that you have.  You must make sure that they, too, receive or
can get the source code.  And you must tell them their rights.

Also, for our own protection, we must make certain that everyone finds
out that there is no warranty for the programs that relate to Texinfo.
If these programs are modified by someone else and passed on, we want
their recipients to know that what they have is not what we distributed,
so that any problems introduced by others will not reflect on our
reputation.

The precise conditions of the licenses for the programs currently
being distributed that relate to Texinfo are found in the General
Public Licenses that accompany them.  This manual is covered by the
GNU Free Documentation License (@pxref{GNU Free Documentation
License}).

@node Overview
@chapter Overview of Texinfo
@cindex Overview of Texinfo
@cindex Texinfo overview
@cindex Using Texinfo in general
@cindex Texinfo, introduction to
@cindex Introduction to Texinfo
@anchor{Using Texinfo} @c merged node

@dfn{Texinfo} is a documentation system that uses a single source file
to produce both online information and printed output.  This means
that instead of writing several different documents, one for each output
format, you need only write one document.

Using Texinfo, you can create a printed document (via the @TeX{}
typesetting system) in PDF or PostScript format, including chapters,
sections, cross-references, and indices.  From the same Texinfo source
file, you can create an HTML output file suitable for use with a web
browser, you can create an Info file with special features to make
browsing documentation easy, and also create a Docbook file or a
transliteration to XML format.

@cindex Source file format
@cindex Semantic markup
A Texinfo source file is a plain text file containing text interspersed
with @dfn{@@-commands} (words preceded by an @samp{@@}) that tell the
Texinfo processors what to do.  Texinfo's markup commands are almost
entirely @dfn{semantic}; that is, they specify the intended meaning
of text in the document, rather than physical formatting instructions.
You can edit a Texinfo file with any text editor, but it is especially
convenient to use GNU Emacs since that editor has a special mode,
called Texinfo mode, that provides various Texinfo-related features.
(@xref{Texinfo Mode}.)

@cindex Limited scope of Texinfo
Texinfo was devised specifically for the purpose of writing software
documentation and manuals.  If you want to write a good manual for
your program, Texinfo has many features which we hope will make your
job easier.  However, it provides almost no commands for controlling
the final formatting.  Texinfo is not intended to be a general-purpose
formatting program, so if you need to lay out a newspaper, devise a
glossy magazine ad, or follow the exact formatting requirements of
a publishing house, Texinfo may not be the simplest tool.

@cindex Spelling of Texinfo
@cindex Pronunciation of Texinfo
Spell ``Texinfo'' with a capital ``T'' and the other letters in
lowercase.  The first syllable of ``Texinfo'' is pronounced like
``speck'', not ``hex''.  This odd pronunciation is derived from the
pronunciation of @TeX{}.  Pronounce @TeX{} as if the @samp{X} were
the last sound in the name `Bach'.  In the word @TeX{}, the @samp{X}
is, rather than the English letter ``ex'', actually the Greek letter
``chi''.

Texinfo is the official documentation format of the GNU project.
More information, including manuals for GNU packages, is available
at the @uref{http://www.gnu.org/doc/, GNU documentation web page}.

@menu
* Reporting Bugs::              Submitting effective bug reports.
* Output Formats::              Overview of the supported output formats.
* Info Files::                  What is an Info file?
* Printed Books::               Characteristics of a printed book or manual.
* Adding Output Formats::       Man pages and implementing new formats.
* History::                     Acknowledgements, contributors and genesis.
@end menu

@node Reporting Bugs
@section Reporting Bugs

@cindex Bugs, reporting
@cindex Suggestions for Texinfo, making
@cindex Reporting bugs
We welcome bug reports and suggestions for any aspect of the Texinfo
system: programs, documentation, installation, etc.  Please email them
to @email{bug-texinfo@@gnu.org}.  You can get the latest version of
Texinfo via its home page, @uref{http://www.gnu.org/software/texinfo}.

@cindex Checklist for bug reports
For bug reports, please include enough information for the maintainers
to reproduce the problem.  Generally speaking, that means:

@itemize @bullet
@item The version number of Texinfo and the program(s) or manual(s) involved.
@item The contents of any input files necessary to reproduce the bug.
@item Precisely how you ran any program(s) involved.
@item A description of the problem and samples of any erroneous output.
@item Hardware and operating system names and versions.
@item Anything else that you think would be helpful.
@end itemize

When in doubt whether something is needed or not, include it.  It's
better to include too much than to leave out something important.

It is critical to send an actual input file that reproduces the
problem.  What's not critical is to ``narrow down'' the example to the
smallest possible input---the actual input with which you discovered
the bug will suffice.  (Of course, if you do do experiments, the
smaller the input file, the better.)

@cindex Patches, contributing
Patches are most welcome; if possible, please make them with
@samp{@w{diff -c}} (@pxref{Top,,, diffutils, Comparing and Merging
Files}) and include @file{ChangeLog} entries (@pxref{Change Log,,,
emacs, The GNU Emacs Manual}), and follow the existing coding style.

@node Output Formats
@section Output Formats
@cindex Output formats
@cindex Back-end output formats

Here is a brief overview of the output formats currently supported by
Texinfo.

@table @asis
@item Info
@cindex Info output, overview
(Generated via @command{makeinfo}.)  Info format is mostly a plain
text transliteration of the Texinfo source.  It adds a few control
characters to provide navigational information for cross-references,
indices, and so on.  The Emacs Info subsystem (@pxref{Top,,, info,
Info}), and the standalone @command{info} program (@pxref{Top,,,
info-stnd, GNU Info}), among others, can read these files.  @xref{Info
Files}, and @ref{Creating and Installing Info Files}.

@item Plain text
@cindex Plain text output, overview
(Generated via @command{makeinfo --plaintext}.)  This is almost the
same as Info output with the navigational control characters are
omitted.

@item HTML
@cindex HTML output, overview
@cindex W3 consortium
@cindex Mozilla
@cindex Lynx
@cindex Emacs-W3
(Generated via @command{makeinfo --html}.)  HTML, standing for Hyper
Text Markup Language, has become the most commonly used language for
writing documents on the World Wide Web.  Web browsers, such as
Mozilla, Lynx, and Emacs-W3, can render this language online.  There
are many versions of HTML, both different standards and
browser-specific variations.  @command{makeinfo} tries to use a subset
of the language that can be interpreted by any common browser,
intentionally not using many newer or less widely-supported tags.
Although the native output is thus rather plain, it can be customized
at various levels, if desired.  For details of the HTML language and
much related information, see @uref{http://www.w3.org/MarkUp/}.
@xref{Generating HTML}.

@item DVI
@cindex DVI output, overview
@pindex dvips
@pindex xdvi
(Generated via @command{texi2dvi}.)  The DeVIce Independent binary
format is output by the @TeX{} typesetting program
(@uref{http://tug.org}).  This is then read by a DVI `driver', which
knows the actual device-specific commands that can be viewed or
printed, notably Dvips for translation to PostScript (@pxref{Top,,,
dvips, Dvips}) and Xdvi for viewing on an X display
(@uref{http://sourceforge.net/projects/xdvi/}).  @xref{Hardcopy}.
(Be aware that the Texinfo language is very different from and much
stricter than @TeX{}'s usual languages: plain @TeX{}, @LaTeX{},
Con@TeX{}t, etc.)

@item PostScript
@cindex PostScript output, overview
(Generated via @command{texi2dvi --ps}.)  PostScript is a page
description language that became widely used around 1985 and is still
used today.  @uref{http://en.wikipedia.org/wiki/PostScript} gives a
basic description and more preferences.  By default, Texinfo uses the
@command{dvips} program to convert @TeX{}'s DVI output to PostScript.
@xref{Top,,, dvips, Dvips}.

@item PDF
@cindex PDF output, overview
@cindex Beebe, Nelson
(Generated via @command{texi2dvi --pdf} or @command{texi2pdf}.)  This
format was developed by Adobe Systems for portable document
interchange, based on their previous PostScript language.  It can
represent the exact appearance of a document, including fonts and
graphics, and supporting arbitrary scaling.  It is intended to be
platform-independent and easily viewable, among other design goals;
@uref{http://en.wikipedia.org/wiki/Portable_Document_Format} and
@uref{http://tug.org/TUGboat/tb22-3/tb72beebe-pdf.pdf} have some
background.  By default, Texinfo uses the @command{pdftex} program, an
extension of @TeX{}, to output PDF; see
@uref{http://tug.org/applications/pdftex}.  @xref{PDF Output}.

@item Docbook
@cindex Docbook output, overview
@cindex XML Docbook output, overview
(Generated via @command{makeinfo --docbook}.)  This is an XML-based
format developed some years ago, primarily for technical
documentation.  It therefore bears some resemblance, in broad
outline, to Texinfo.  See @uref{http://www.docbook.org}.  Various
converters from Docbook @emph{to} Texinfo have also been developed;
see the Texinfo web pages.

@item XML
@cindex XML Texinfo output, overview
@cindex Texinfo XML output, overview
@cindex DTD, for Texinfo XML
@pindex texinfo.dtd
@pindex txixml2texi
(Generated via @command{makeinfo --xml}.)  XML is a generic syntax
specification usable for any sort of content (a reference is at
@uref{http://www.w3.org/XML}).  The @command{makeinfo} XML output,
unlike all the other output formats, is a transliteration of the
Texinfo source rather than processed output.  That is, it translates
the Texinfo markup commands into XML syntax, for further processing by
XML tools.  The XML contains enough information to recreate the
original content, except for syntactic constructs such as Texinfo
macros and conditionals.  The Texinfo source distribution includes a
utility script @file{txixml2texi} to do that backward transformation.

The details of the output syntax are defined in an XML DTD as usual,
which is contained in a file @file{texinfo.dtd} included in the
Texinfo source distribution and available via the Texinfo web pages.
Texinfo XML files, and XML files in general, cannot be viewed in
typical web browsers; they won't follow the DTD reference and as a
result will simply report a (misleading) syntax error.
@end table

@node Info Files
@section Info Files
@cindex Info files

As mentioned above, Info format is mostly a plain text transliteration
of the Texinfo source, with the addition of a few control characters
to separate nodes and provide navigational information, so that
Info-reading programs can operate on it.

Info files are nearly always created by processing a Texinfo source
document.  @command{makeinfo}, also known as @command{texi2any}, is
the principal command that converts a Texinfo file into an Info file;
@pxref{Generic Translator @command{texi2any}}.

Generally, you enter an Info file through a node that by convention is
named `Top'.  This node normally contains just a brief summary of the
file's purpose, and a large menu through which the rest of the file is
reached.  From this node, you can either traverse the file
systematically by going from node to node, or you can go to a specific
node listed in the main menu, or you can search the index menus and then
go directly to the node that has the information you want.  Alternatively,
with the standalone Info program, you can specify specific menu items on
the command line (@pxref{Top,,, info, Info}).

If you want to read through an Info file in sequence, as if it were a
printed manual, you can hit @key{SPC} repeatedly, or you get the whole
file with the advanced Info command @kbd{g *}.  (@xref{Advanced,,
Advanced Info commands, info, Info}.)

The @file{dir} file in the @file{info} directory serves as the
departure point for the whole Info system.  From it, you can reach the
`Top' nodes of each of the documents in a complete Info system.

@cindex URI syntax for Info
If you wish to refer to an Info file via a URI, you can use the
(unofficial) syntax exemplified by the following.  This works with
Emacs/W3, for example:
@example
info:emacs#Dissociated%20Press
info:///usr/info/emacs#Dissociated%20Press
info://localhost/usr/info/emacs#Dissociated%20Press
@end example

The @command{info} program itself does not follow URIs of any kind.

@node Printed Books
@section Printed Books
@cindex Printed book and manual characteristics
@cindex Manual characteristics, printed
@cindex Book characteristics, printed
@cindex Texinfo printed book characteristics
@cindex Characteristics, printed books or manuals

@cindex Knuth, Donald
A Texinfo file can be formatted and typeset as a printed book or
manual.  To do this, you need @TeX{}, a sophisticated typesetting
program written by Donald Knuth of Stanford University.

A Texinfo-based book is similar to any other typeset, printed work: it
can have a title page, copyright page, table of contents, and preface,
as well as chapters, numbered or unnumbered sections and subsections,
page headers, cross-references, footnotes, and indices.

@TeX{} is a general purpose typesetting program.  Texinfo provides a
file @file{texinfo.tex} that contains information (definitions or
@dfn{macros}) that @TeX{} uses when it typesets a Texinfo file.
(@file{texinfo.tex} tells @TeX{} how to convert the Texinfo @@-commands
to @TeX{} commands, which @TeX{} can then process to create the typeset
document.)  @file{texinfo.tex} contains the specifications for printing
a document.  You can get the latest version of @file{texinfo.tex} from
the Texinfo home page, @uref{http://www.gnu.org/software/texinfo/}.

In the United States, documents are most often printed on 8.5 inch by
11 inch pages (216@dmn{mm} by 280@dmn{mm}); this is the default size.
But you can also print for 7 inch by 9.25 inch pages (178@dmn{mm} by
235@dmn{mm}, the @code{@@smallbook} size; or on A4 or A5 size paper
(@code{@@afourpaper}, @code{@@afivepaper}).
@xref{@code{@@smallbook}}, and @ref{A4 Paper}.

@cindex Literate programming
@TeX{} is freely distributable.  It is written in a superset of Pascal
for literate programming called WEB and can be compiled either in
Pascal or (by using a conversion program that comes with the @TeX{}
distribution) in C.

@TeX{} is very powerful and has a great many features.  Because a
Texinfo file must be able to present information both on a
character-only terminal in Info form and in a typeset book, the
formatting commands that Texinfo supports are necessarily limited.

@xref{Obtaining @TeX{}}, for information on acquiring @TeX{}.  It is
not part of the Texinfo distribution.

@node Adding Output Formats
@section Adding Output Formats
@cindex Additional output formats

The output formats in the previous sections handle a wide variety of
usage, but of course there is always room for more.

@cindex Output formats, supporting more
@cindex SGML-tools output format
If you are a programmer and would like to contribute to the GNU
project by implementing additional output formats for Texinfo, that
would be excellent.  The way to do this that would be most useful is
to write a new back-end for @command{texi2any}, our reference
implementation of a Texinfo parser; it creates a tree representation
of the Texinfo input that you can use for the conversion.  The
documentation in the source file
@file{tp/Texinfo/Convert/Converter.pm} is a good place to start.
@xref{Generic Translator @command{texi2any}}.

Another viable approach is use the Texinfo XML output from
@command{texi2any} as your input.  This XML is an essentially complete
representation of the input, but without the Texinfo syntax and option
peculiarities, as described above.

@cindex Texinfo parsers, discouraging more
If you still cannot resist the temptation of writing a new program
that reads Texinfo source directly, let us give some more caveats:
please do not underestimate the amount of work required.  Texinfo is
by no means a simple language to parse correctly, and remains under
development, so you would be committing to an ongoing task.  You
are advised to check that the tests of the language that come with
@command{texi2any} give correct results with your new program.

@cindex Man page output, not supported
From time to time, proposals are made to generate traditional Unix man
pages from Texinfo source.  However, because man pages have a strict
conventional format, creating a good man page requires a completely
different source from that needed for the typical Texinfo applications
of writing a good user tutorial and/or a good reference manual.  This
makes generating man pages incompatible with the Texinfo design
goal of not having to document the same information in different
ways for different output formats.  You might as well write the man
page directly.

@pindex help2man
@cindex O'Dea, Brendan
As an alternative way to support man pages, you may find the program
@command{help2man} to be useful.  It generates a traditional man page
from the @samp{--help} output of a program.  In fact, the man pages
for the programs in the Texinfo distribution are generated with this.
It is GNU software written by Brendan O'Dea, available from
@uref{http://www.gnu.org/software/help2man}.

@node History
@section History

@cindex Stallman, Richard M.
@cindex Chassell, Robert J.
@cindex Fox, Brian
@cindex Berry, Karl
Richard M. Stallman invented the Texinfo format, wrote the initial
processors, and created Edition 1.0 of this manual.  Robert@tie{}J.
Chassell greatly revised and extended the manual, starting with
Edition 1.1.  Brian Fox was responsible for the standalone Texinfo
distribution until version 3.8, and originally wrote the standalone
@command{makeinfo} and @command{info} programs.  Karl Berry has
continued maintenance since Texinfo 3.8 (manual edition 2.22).

@cindex Pinard, Fran@,{c}ois
@cindex Schwab, Andreas
@cindex Weinberg, Zack
@cindex Weisshaus, Melissa
@cindex Zaretskii, Eli
@cindex Zuhn, David D.
Our thanks go out to all who helped improve this work, particularly
the indefatigable Eli Zaretskii and Andreas Schwab, who have provided
patches beyond counting.  Fran@,{c}ois Pinard and David@tie{}D. Zuhn,
tirelessly recorded and reported mistakes and obscurities.  Zack
Weinberg did the impossible by implementing the macro syntax in
@file{texinfo.tex}.  Thanks to Melissa Weisshaus for her frequent
reviews of nearly similar editions.  Dozens of others have contributed
patches and suggestions, they are gratefully acknowledged in the
@file{ChangeLog} file.  Our mistakes are our own.

@cindex History of Texinfo
@cindex Texinfo history
@subheading Beginnings

@cindex Scribe
@cindex Reid, Brian
In the 1970's at CMU, Brian Reid developed a program and format named
Scribe to mark up documents for printing.  It used the @code{@@}
character to introduce commands, as Texinfo does.  Much more
consequentially, it strove to describe document contents rather than
formatting, an idea wholeheartedly adopted by Texinfo.

@cindex Bolio
@cindex Bo@TeX{}
Meanwhile, people at MIT developed another, not too dissimilar format
called Bolio.  This then was converted to using @TeX{} as its typesetting
language: Bo@TeX{}.  The earliest Bo@TeX{} version seems to have been
0.02 on October 31, 1984.

Bo@TeX{} could only be used as a markup language for documents to be
printed, not for online documents.  Richard Stallman (RMS) worked on
both Bolio and Bo@TeX{}.  He also developed a nifty on-line help format
called Info, and then combined Bo@TeX{} and Info to create Texinfo, a
mark up language for text that is intended to be read both online and
as printed hard copy.

Moving forward, the original translator to create Info was written
(primarily by RMS and Bob Chassell) in Emacs Lisp, namely the
@code{texinfo-format-buffer} and other functions.  In the early 1990s,
Brian Fox reimplemented the conversion program in C, now called
@command{makeinfo}.

@subheading Reimplementing in Perl

@cindex Cons, Lionel
@cindex Dumas, Patrice
In 2012, the C @command{makeinfo} was itself replaced by a Perl
implementation generically called @command{texi2any}.  This version
supports the same level of output customization as
@command{texi2html}, an independent program originally written by
Lionel Cons, later with substantial work by many others.  The many
additional features needed to make @command{texi2html} a replacement
for @command{makeinfo} were implemented by Patrice Dumas.  The first
never-released version of @command{texi2any} was based on the
@command{texi2html} code.  That implementation, however, was abandoned
in favor of the current program, which parses the Texinfo input into a
tree for processing.  It still supports nearly all the features of
@command{texi2html}.

The new Perl program is much slower than the old C program.  We hope
the speed gap will close in the future, but it may not ever be
entirely comparable.  So why did we switch?  In short, we intend and
hope that the present program will be much easier than the previous C
implementation of @command{makeinfo} to extend to different output
styles, back-end output formats, and all other customizations.
In more detail:

@itemize @bullet
@item HTML customization.  Many GNU and other free software packages
had been happily using the HTML customization features in
@command{texi2html} for years.  Thus, in effect two independent
implementations of the Texinfo language had developed, and keeping
them in sync was not simple.  Adding the HTML customization possible
in @command{texi2html} to a C program would have been an
enormous effort.

@item Unicode, and multilingual support generally, especially of east
Asian languages.  Although of course it's perfectly plausible to write
such support in C, in the particular case of @command{makeinfo}, it
would have been tantamount to rewriting the entire program.  In Perl,
much of that comes essentially for free.

@item Additional back-ends.  The @command{makeinfo} code had become
convoluted to the point where adding a new back-end was quite complex,
requiring complex interactions with existing back-ends.  In contrast,
our Perl implementation provides a clean tree-based representation for
all back-ends to work from.  People have requested numerous different
back-ends (@LaTeX{}, the latest (X)HTML, @dots{}), and they will now
be much more feasible to implement.  Which leads to the last item:

@item Making contributions easier.  In general, due to the cleaner
structure, the Perl program should be considerably easier than the C
for anyone to read and contribute to, with the resulting obvious
benefits.
@end itemize

@xref{Reference Implementation}, for more on the rationale for and
role of @command{texi2any}.

@node Writing a Texinfo File
@chapter Writing a Texinfo File

This chapter describes Texinfo syntax and what is required in a Texinfo
file, and gives a short sample file.

@menu
* Conventions::                 General rules for writing a Texinfo file.
* Comments::                    Writing comments and ignored text in general.
* Minimum::                     What a Texinfo file must have.
* Short Sample::                A short sample Texinfo file.
@end menu

@node Conventions
@section General Syntactic Conventions
@cindex General syntactic conventions
@cindex Syntactic conventions
@cindex Conventions, syntactic
@cindex Characters, basic input
@anchor{Formatting Commands} @c old name

This section describes the general conventions used in all Texinfo documents.

@itemize @bullet
@item
@cindex Source files, characters used
All printable ASCII characters except @samp{@@}, @samp{@{} and
@samp{@}} can appear in a Texinfo file and stand for themselves.
@samp{@@} is the escape character which introduces commands, while
@samp{@{} and @samp{@}} are used to surround arguments to certain
commands.  To put one of these special characters into the document, put
an @samp{@@} character in front of it, like this: @samp{@@@@},
@samp{@@@{}, and @samp{@@@}}.

@item
@cindex @@-commands
@cindex Formatting commands
In a Texinfo file, the commands you write to describe the contents of
the manual are preceded by an @samp{@@} character; they are called
@dfn{@@-commands}.  (The @samp{@@} in Texinfo has the same meaning that
@samp{\} has in plain @TeX{}.)

@cindex Braces, when to use
Depending on what they do or what arguments@footnote{The word
@dfn{argument} comes from the way it is used in mathematics and does not
refer to a dispute between two people; it refers to the information
presented to the command.  According to the @cite{Oxford English
Dictionary}, the word derives from the Latin for @dfn{to make clear,
prove}; thus it came to mean `the evidence offered as proof', which is
to say, `the information offered', which led to its mathematical
meaning.  In its other thread of derivation, the word came to mean `to
assert in a manner against which others may make counter assertions',
which led to the meaning of `argument' as a dispute.} they take, you
need to write @@-commands on lines of their own, or as part of
sentences.  As a general rule, a command requires braces if it mingles
among other text; but it does not need braces if it is on a line of its
own.  For more details of Texinfo command syntax, see @ref{Command
Syntax}.

@item
Whitespace following an @@-command name is optional and (usually)
ignored if present.  The exceptions are contexts when whitespace is
significant, e.g., an @code{@@example} environment.

@item
Texinfo supports the usual quotation marks used in English and in
other languages; see @ref{Inserting Quotation Marks}.

@item
@cindex Multiple dashes in source
@cindex Dashes in source
@cindex Hyphens in source, two or three in a row
@cindex Em dash, producing
@cindex En dash, producing
Use three hyphens in a row, @samp{---}, to produce a long dash---like
this (called an @dfn{em dash}), used for punctuation in sentences.
Use two hyphens, @samp{--}, to produce a medium dash (called an
@dfn{en dash}), used primarily for numeric ranges, as in ``June
25--26''.  Use a single hyphen, @samp{-}, to produce a standard hyphen
used in compound words.  For display on the screen, Info reduces three
hyphens to two and two hyphens to one (not transitively!).  Of course,
any number of hyphens in the source remain as they are in literal
contexts, such as @code{@@code} and @code{@@example}.

@item
@cindex Form feed characters
@cindex @kbd{CTRL-l}
Form feed (@kbd{CTRL-l}) characters in the input are handled as
follows:

@table @asis
@item PDF/DVI
In normal text, treated as ending any open paragraph; essentially
ignored between paragraphs.

@item Info
Output as-is between paragraphs (their most common use); in other
contexts, they may be treated as regular spaces (and thus consolidated
with surrounding whitespace).

@item HTML
Written as a numeric entity except contexts where spaces are ignored;
for example, in @samp{@@footnote@{ ^L foo@}}, the form feed is
ignored.

@item XML
Keep them everywhere; in attributes, escaped as @samp{\f}; also,
@samp{\} is escaped as @samp{\\} and newline as @samp{\n}.

@item Docbook
Completely removed, as they are not allowed.
@end table

As you can see, because of these differing requirements of the output
formats, it's not possible to use form feeds completely portably.

@item
@cindex Tabs; don't use!
@strong{Caution:} Last, do not use tab characters in a Texinfo file!
(Except perhaps in verbatim modes.)  @TeX{} uses variable-width fonts,
which means that it is impractical at best to define a tab to work in
all circumstances.  Consequently, @TeX{} treats tabs like single
spaces, and that is not what they look like in the source.
Furthermore, @code{makeinfo} does nothing special with tabs, and thus
a tab character in your input file will usually have a different
appearance in the output.

@noindent
To avoid this problem, Texinfo mode in GNU Emacs inserts
multiple spaces when you press the @key{TAB} key.  Also, you can run
@code{untabify} in Emacs to convert tabs in a region to multiple
spaces, or use the @code{unexpand} command from the shell.
@end itemize

@node Comments
@section Comments

@cindex Comments
@findex comment
@findex c

You can write comments in a Texinfo file by using the @code{@@comment}
command, which may be abbreviated to @code{@@c}.  Such comments are
for a person looking at the Texinfo source file.  All the text on a
line that follows either @code{@@comment} or @code{@@c} is a comment;
the rest of the line does not appear in the visible output.  (To be
precise, the character after the @code{@@c} or @code{@@comment} must
be something other than a dash or alphanumeric, or it will be taken as
part of the command.)

Often, you can write the @code{@@comment} or @code{@@c} in the middle
of a line, and only the text that follows after the @code{@@comment}
or @code{@@c} command does not appear; but some commands, such as
@code{@@settitle}, work on a whole line.  You cannot use @code{@@comment}
or @code{@@c} within a line beginning with such a command.

@findex DEL @r{(comment character)}
@cindex Catcode for comments in @TeX{}
In cases of nested command invocations, complicated macro definitions,
etc., @code{@@c} and @code{@@comment} may provoke an error when
processing with @TeX{}.  Therefore, you can also use the @kbd{DEL}
character (ASCII 127 decimal, 0x7f hex, 0177 octal) as a true @TeX{}
comment character (catcode 14, in @TeX{} internals).  Everything on
the line after the @kbd{DEL} will be ignored.

@cindex Ignored text
@cindex Unprocessed text
@findex ignore
You can also have long stretches of text ignored by the Texinfo
processors with the @code{@@ignore} and @code{@@end ignore} commands.
Write each of these commands on a line of its own, starting each
command at the beginning of the line.  Text between these two commands
does not appear in the processed output.  You can use @code{@@ignore}
and @code{@@end ignore} for writing comments.  (For some caveats
regarding nesting of such commands, @pxref{Conditional Nesting}.)

@node Minimum
@section What a Texinfo File Must Have
@cindex Minimal Texinfo file (requirements)
@cindex Must have in Texinfo file
@cindex Required in Texinfo file
@cindex Texinfo file minimum

By convention, the name of a Texinfo file ends with one of the
extensions @file{.texinfo}, @file{.texi}, @file{.txi}, or
@file{.tex}.@footnote{The longer extensions are preferred, since they
describe more clearly to a human reader the nature of the file.  The
shorter extensions are for operating systems that cannot handle long
file names.}

In order to be made into a printed manual and other output
formats, a Texinfo file must begin with lines like this:

@example
@group
\input texinfo
@@settitle @var{name-of-manual}
@end group
@end example

@noindent
The contents of the file follow this beginning, and then you
must end the Texinfo source with a line like this:

@example
@@bye
@end example

@findex \input @r{(raw @TeX{} startup)}
@noindent
Here's an explanation:

@itemize @bullet
@item
The @samp{\input texinfo} line tells @TeX{} to use the
@file{texinfo.tex} file, which tells @TeX{} how to translate the Texinfo
@@-commands into @TeX{} typesetting commands.  (Note the use of the
backslash, @samp{\}; this is correct for @TeX{}.)

@item
The @code{@@settitle} line specifies a title for the page headers (or
footers) of the printed manual, and the default title and document
description for the @samp{<head>} in HTML@.  Strictly speaking,
@code{@@settitle} is optional---if you don't mind your document being
titled `Untitled'.

@item
The @code{@@bye} line at the end of the file on a line of its own tells
the formatters that the file is ended and to stop formatting.  If you
leave this out, you'll be dumped at @TeX{}'s prompt at the end of the
run.
@end itemize

Furthermore, you will usually provide a Texinfo file with a title page,
indices, and the like, all of which are explained in this manual.  But
the minimum, which can be useful for short documents, is just the two
lines at the beginning and the one line at the end.

@node Short Sample
@section A Short Sample Texinfo File
@cindex Sample Texinfo file, with comments

Here is a short but complete Texinfo file, so you can see how Texinfo
source appears in practice.  The first three parts of the file are
mostly boilerplate: when writing a manual, you simply change
the names as appropriate.

The complete file, without interspersed comments, is shown in
@ref{Short Sample Texinfo File}.

@xref{Beginning and Ending a File}, for more documentation on the
commands listed here.

@subheading Header

@noindent
The header tells @TeX{} which definitions file to
use, names the manual, and carries out other such housekeeping tasks.

@example
@group
\input texinfo
@@settitle Sample Manual 1.0
@end group
@end example

@subheading Summary Description and Copyright

This segment describes the document and contains the copyright notice
and copying permissions.  This is done with the @code{@@copying} command.

@noindent
A real manual includes more text here, according to the license under
which it is distributed.  @xref{GNU Sample Texts}.

@example
@group
@@copying
This is a short example of a complete Texinfo file, version 1.0.

Copyright @@copyright@{@} 2016 Free Software Foundation, Inc.
@@end copying
@end group
@end example

@subheading Titlepage, Copyright, Contents

The title and copyright segment contains the title and copyright
pages for the printed manual.  The segment must be enclosed between
@code{@@titlepage} and @code{@@end titlepage} commands.  The title and
copyright page does not appear in the online output.

@noindent
We use the @code{@@insertcopying} command to
include the permission text from the previous section, instead of
writing it out again; it is output on the back of the title page.  The
@code{@@contents} command generates a table of contents.

@example
@group
@@titlepage
@@title Sample Title
@end group

@group
@@c The following two commands start the copyright page.
@@page
@@vskip 0pt plus 1filll
@@insertcopying
@@end titlepage
@end group

@@c Output the table of contents at the beginning.
@@contents
@end example

@subheading `Top' Node and Master Menu

The `Top' node starts off the online output; it does not appear in the
printed manual.  We repeat the short description from the beginning of
the @samp{@@copying} text, but there's no need to repeat the copyright
information, so we don't use @samp{@@insertcopying} here.

The @samp{@@top} command itself helps @command{makeinfo} determine
the relationships between nodes.  The `Top' node contains at least a
top-level @dfn{menu} listing the chapters, and possibly a @dfn{Master
Menu} listing all the nodes in the entire document.

@example
@@ifnottex
@@node Top
@@top Short Sample

This is a short sample Texinfo file.
@@end ifnottex

@group
@@menu
* First Chapter::    The first chapter is the
                       only chapter in this sample.
* Index::            Complete index.
@@end menu
@end group
@end example

@subheading The Body of the Document

@noindent
The body segment contains all the text of the document, but not the
indices or table of contents.  This example illustrates a node and a
chapter containing an enumerated list.

@example
@group
@@node First Chapter
@@chapter First Chapter

@@cindex chapter, first
@end group

@group
This is the first chapter.
@@cindex index entry, another
@end group

@group
Here is a numbered list.

@@enumerate
@@item
This is the first item.

@@item
This is the second item.
@@end enumerate
@end group
@end example

@subheading The End of the Document

This may contain commands for printing indices, and
closes with the @code{@@bye} command, which marks the end of the document.

@example
@group
@@node Index
@@unnumbered Index
@end group

@group
@@printindex cp

@@bye
@end group
@end example

@subheading Some Results

Here is what the contents of the first chapter of the sample look like:

@sp 1
@need 700
@quotation
This is the first chapter.

Here is a numbered list.

@enumerate
@item
This is the first item.

@item
This is the second item.
@end enumerate
@end quotation

@node Beginning and Ending a File
@anchor{Beginning a File} @c old name
@chapter Beginning and Ending a Texinfo File
@cindex Beginning a Texinfo file
@cindex Texinfo file beginning
@cindex File beginning

This chapter expands on the minimal complete Texinfo source file
previously given (@pxref{Short Sample}).

Certain pieces of information must be provided at the beginning of a
Texinfo file, such the title of the document and the Top node.  A table
of contents is also generally produced here.

@cindex Frontmatter, text in
Straight text outside of any command before the Top node should be
avoided.  Such text is treated differently in the different output
formats: at the time of writing, it is visible in @TeX{} and HTML, by
default not shown in Info readers, and so on.

@menu
* Sample Beginning::            A sample beginning for a Texinfo file.
* Texinfo File Header::         The first lines.
* Document Permissions::        Ensuring your manual is free.
* Titlepage & Copyright Page::  Creating the title and copyright pages.
* Contents::                    How to create a table of contents.
* The Top Node::                Creating the `Top' node and master menu.
* Global Document Commands::    Affecting formatting throughout.
* Ending a File::               What is at the end of a Texinfo file?
@end menu

@node Sample Beginning
@section Sample Texinfo File Beginning

@cindex Example beginning of Texinfo file

The following sample shows what is needed.  The elements given here are
explained in more detail in the following sections.  Other commands are
often included at the beginning of Texinfo files, but the ones here are
the most critical.

@xref{GNU Sample Texts}, for the full texts to be used in GNU manuals.

@example
\input texinfo
@@settitle @var{name-of-manual} @var{version}

@@copying
This manual is for @var{program}, version @var{version}.

Copyright @@copyright@{@} @var{years} @var{copyright-owner}.

@group
@@quotation
Permission is granted to @dots{}
@@end quotation
@@end copying
@end group

@group
@@titlepage
@@title @var{name-of-manual-when-printed}
@@subtitle @var{subtitle-if-any}
@@subtitle @var{second-subtitle}
@@author @var{author}
@end group

@group
@@c  The following two commands
@@c  start the copyright page.
@@page
@@vskip 0pt plus 1filll
@@insertcopying
@end group

Published by @dots{}
@@end titlepage

@@c So the toc is printed at the start.
@@contents

@@ifnottex
@@node Top
@@top @var{title}

This manual is for @var{program}, version @var{version}.
@@end ifnottex

@group
@@menu
* First Chapter::    Getting started @dots{}
* Second Chapter::          @dots{}
 @dots{}
* Copying::          Your rights and freedoms.
@@end menu
@end group

@group
@@node First Chapter
@@chapter First Chapter

@@cindex first chapter
@@cindex chapter, first
@dots{}
@end group
@end example

@node Texinfo File Header
@section Texinfo File Header
@cindex Header for Texinfo files
@cindex Texinfo file header

Texinfo files start with at least two lines.  These are the
@code{\input texinfo} line and the @code{@@settitle} line.

Also, if you want to format just part of the Texinfo file in Emacs,
you must write the @code{@@settitle} line between start-of-header and
end-of-header lines.  These start- and end-of-header lines are optional,
but they do no harm, so you might as well always include them.

Any command that affects document formatting as a whole makes sense to
include in the header.  @code{@@synindex} (@pxref{@code{@@synindex}}),
for instance, is another command often included in the header.

Thus, the beginning of a Texinfo file looks approximately
like this:

@example
@group
\input texinfo
@@settitle Sample Manual 1.0
@end group
@end example

(@xref{GNU Sample Texts} for complete sample texts.)

@menu
* First Line::                  The first line of a Texinfo file.
* Start of Header::             Formatting a region requires this.
* @code{@@setfilename}::                Tell Info the name of the Info file.
* @code{@@settitle}::                   Create a title for the printed work.
* End of Header::               Formatting a region requires this.
@end menu

@node First Line
@subsection The First Line of a Texinfo File
@cindex First line of a Texinfo file
@cindex Beginning line of a Texinfo file
@cindex Header of a Texinfo file

Every Texinfo file that is to be the top-level input to @TeX{} must begin
with a line that looks like this:

@example
\input texinfo
@end example

When the file is processed by @TeX{}, the @samp{\input texinfo} command
tells @TeX{} to load the macros needed for processing a Texinfo file.
These are in a file called @file{texinfo.tex}, which should have been
installed on your system along with either the @TeX{} or Texinfo
software.  @TeX{} uses the backslash, @samp{\}, to mark the beginning of
a command, exactly as Texinfo uses @samp{@@}.  The @file{texinfo.tex}
file causes the switch from @samp{\} to @samp{@@}; before the switch
occurs, @TeX{} requires @samp{\}, which is why it appears at the
beginning of the file.

You may optionally follow this line with a comment to tell GNU Emacs
to use Texinfo mode when the file is edited:

@example
\input texinfo   @@c -*-texinfo-*-
@end example

@noindent This may be useful when Emacs doesn't detect the file type
from the file extension automatically.

@node Start of Header
@subsection Start of Header
@cindex Start of header line

A start-of-header line is a Texinfo comment that looks like this:

@example
@@c %**start of header
@end example

Write the start-of-header line on the second line of a Texinfo file.
Follow the start-of-header line with an @code{@@settitle} line and,
optionally, with other commands that globally affect the document
formatting, such as @code{@@synindex} or @code{@@footnotestyle}; and
then by an end-of-header line (@pxref{End of Header}).

The start- and end-of-header lines allow you to format only part of a
Texinfo file for Info or printing.  @xref{@code{texinfo-format} commands}.

The odd string of characters, @samp{%**}, is to ensure that no other
comment is accidentally taken for a start-of-header line.  You can
change it if you wish by setting the @code{tex-start-of-header} and/or
@code{tex-end-of-header} Emacs variables.  @xref{Texinfo Mode Printing}.

@node @code{@@setfilename}
@subsection @code{@@setfilename}: Set the Output File Name

@anchor{setfilename}@c old name
@findex setfilename
@cindex Texinfo requires @code{@@setfilename}
@cindex Output file name, required

The @code{@@setfilename} line specifies the name of the output file to
be generated.
When present, it should be the first Texinfo command (that is, after
@samp{\input texinfo}).
Write the @code{@@setfilename} command at the beginning of a line and
follow it on the same line by the Info file name.

@example
@@setfilename @var{info-file-name}
@end example

The name must be different from the name of the
Texinfo file.  There are two conventions for choosing the name: you
can either remove the extension (such as @samp{.texi}) entirely from
the input file name, or (recommended) replace it with the @samp{.info}
extension.

@cindex Ignored before @code{@@setfilename}
@cindex @samp{\input} source line ignored
When a @code{@@setfilename} line is present, the Texinfo processors
ignore everything written before the @code{@@setfilename} line.  This
is why the very first line of the file (the @code{\input} line) does
not show up in the output.

If there is no @code{@@setfilename} line, @code{makeinfo} uses the
input file name to determine the output name: first, any of the
extensions @code{.texi}, @code{.tex}, @code{.txi} or @code{.texinfo}
is removed from the input file name; then, the output format specific
extension is added---@code{.html} when generating HTML, @code{.info}
when generating Info, etc.  The @code{\input} line is still ignored in
this processing, as well as leading blank lines.

When producing another output format, @code{makeinfo} will replace any
final extension with the output format-specific extension (@samp{html}
when generating HTML, for example), or add a dot followed by the
extension (@samp{.html} for HTML) if the given name has no extension.

@code{@@setfilename} used to be required by the Texinfo processors, and
some other programs may still expect it to be present; for example,
Automake (@pxref{Texinfo,,,automake, GNU Automake}).

@cindex Length of file names
@cindex File name collision
@cindex Info file name, choosing
Although an explicit @samp{.info} extension is preferable, some
operating systems cannot handle long file names.  You can run into a
problem even when the file name you specify is itself short enough.
This occurs because the Info formatters split a long Info file into
short indirect subfiles, and name them by appending @samp{-1},
@samp{-2}, @dots{}, @samp{-10}, @samp{-11}, and so on, to the original
file name.  (@xref{Tag and Split Files}.)  The subfile name
@file{texinfo.info-10}, for example, is too long for old systems with
a 14-character limit on filenames; so the Info file name for this
document is @file{texinfo} rather than @file{texinfo.info}.  When
@code{makeinfo} is running on operating systems such as MS-DOS which
impose severe limits on file names, it may remove some characters from
the original file name to leave enough space for the subfile suffix,
thus producing files named @file{texin-10}, @file{gcc.i12}, etc.

See also the @option{--output} option in @ref{Invoking @command{texi2any}}.

@node @code{@@settitle}
@subsection @code{@@settitle}: Set the Document Title

@anchor{settitle}@c old name
@findex settitle
@cindex Document title, specifying

A Texinfo file should contain a line that looks like this:

@example
@@settitle @var{title}
@end example

Write the @code{@@settitle} command at the beginning of a line and
follow it on the same line by the title.  Do not write anything else
on the line.  The @code{@@settitle} command should precede everything
that generates actual output.  The best place for it is right after
the @code{@@setfilename} command (described in the previous section).

This command tells @TeX{} the title to use in a header or footer
for double-sided output, in case such headings are output.  For
more on headings for @TeX{}, see @ref{Heading Generation}.

@cindex @code{<title>} HTML tag
In the HTML file produced by @command{makeinfo}, @var{title} serves as
the document @samp{<title>}.  It also becomes the default document
description in the @samp{<head>} part
(@pxref{@code{@@documentdescription}}).

When the title page is used in the output, the title in the
@code{@@settitle} command does not affect the title as it appears on
the title page.  Thus, the two do not need not to match exactly.  A
practice we recommend is to include the version or edition number of
the manual in the @code{@@settitle} title; on the title page, the
version number generally appears as a @code{@@subtitle} so it would
be omitted from the @code{@@title}.  @xref{@code{@@titlepage}}.

@node End of Header
@subsection End of Header
@cindex End of header line

Follow the header lines with an @w{end-of-header} line, which is a
Texinfo comment that looks like this:

@example
@@c %**end of header
@end example

@xref{Start of Header}.

@node Document Permissions
@section Document Permissions
@cindex Document Permissions
@cindex Copying Permissions

The copyright notice and copying permissions for a document need to
appear in several places in the various Texinfo output formats.
Therefore, Texinfo provides a command (@code{@@copying}) to declare
this text once, and another command (@code{@@insertcopying}) to
insert the text at appropriate points.

@anchor{Software Copying Permissions}@c old node name
This section is about the license of the Texinfo document.  If the
document is a software manual, the software is typically under a
different license---for GNU and many other free software packages,
software is usually released under the GNU GPL, and manuals are
released under the GNU FDL@.  It is helpful to state the license of
the software of the manual, but giving the complete text of the
software license is not necessarily required.

@menu
* @code{@@copying}::                    Declare the document's copying permissions.
* @code{@@insertcopying}::              Where to insert the permissions.
@end menu

@node @code{@@copying}
@subsection @code{@@copying}: Declare Copying Permissions

@anchor{copying}@c old name
@findex copying

The @code{@@copying} command should be given very early in the document;
the recommended location is right after the header material
(@pxref{Texinfo File Header}).  It conventionally consists of a sentence
or two about what the program is, identification of the documentation
itself, the legal copyright line, and the copying permissions.  Here is
a skeletal example:

@example
@@copying
This manual is for @var{program} (version @var{version}, updated
@var{date}), which @dots{}

Copyright @@copyright@{@} @var{years} @var{copyright-owner}.

@@quotation
Permission is granted to @dots{}
@@end quotation
@@end copying
@end example

The @code{@@quotation} has no legal significance; it's there to improve
readability in some contexts.

The text of @code{@@copying} is output as a comment at the beginning
of Info, HTML, XML, and Docbook output files.  It is @emph{not} output
implicitly in plain text or @TeX{}; it's up to you to use
@code{@@insertcopying} to emit the copying information.  See the next
section for details.

@findex copyright
The @code{@@copyright@{@}} command generates a @samp{c} inside a
circle when the output format supports this glyph (print and HTML
always do, for instance).  When the glyph is not supported in the
output, it generates the three-character sequence @samp{(C)}.

The copyright notice itself has the following legally-prescribed
form:

@example
Copyright @copyright{} @var{years} @var{copyright-owner}.
@end example

@cindex Copyright word, always in English
The word `Copyright' must always be written in English, even if the
document is otherwise written in another language.  This is due to
international law.

@cindex Years, in copyright line
The list of years should include all years in which a version was
completed (even if it was released in a subsequent year).  It is
simplest for each year to be written out individually and in full,
separated by commas.

@cindex Copyright holder for FSF works
@cindex Holder of copyright for FSF works
@cindex Owner of copyright for FSF works
The copyright owner (or owners) is whoever holds legal copyright on the
work.  In the case of works assigned to the FSF, the owner is `Free
Software Foundation, Inc.'.

The copyright `line' may actually be split across multiple lines, both
in the source document and in the output.  This often happens for
documents with a long history, having many different years of
publication.  If you do use several lines, do not indent any of them
(or anything else in the @code{@@copying} block) in the source file.

@xref{Copyright Notices,,, maintain, GNU Maintainer Information}, for
additional information.  @xref{GNU Sample Texts}, for the full text to
be used in GNU manuals.  @xref{GNU Free Documentation License}, for
the license itself under which GNU and other free manuals are
distributed.

@node @code{@@insertcopying}
@subsection @code{@@insertcopying}: Include Permissions Text

@anchor{insertcopying}@c old name
@findex insertcopying
@cindex Copying text, including
@cindex Permissions text, including
@cindex Including permissions text

The @code{@@insertcopying} command is simply written on a line by
itself, like this:

@example
@@insertcopying
@end example

This inserts the text previously defined by @code{@@copying}.  To meet
legal requirements, it must be used on the copyright page in the printed
manual (@pxref{Copyright}).

The @code{@@copying} command itself causes the permissions text to
appear in an Info file @emph{before} the first node.  The text is also
copied into the beginning of each split Info output file, as is legally
necessary.  This location implies a human reading the manual using Info
does @emph{not} see this text (except when using the advanced Info
command @kbd{g *}), but this does not matter for legal purposes,
because the text is present.

Similarly, the @code{@@copying} text is automatically included at the
beginning of each HTML output file, as an HTML comment.  Again, this
text is not visible (unless the reader views the HTML source).

The permissions text defined by @code{@@copying} also appears
automatically at the beginning of the XML and Docbook output files.

@node Titlepage & Copyright Page
@section Title and Copyright Pages

In hard copy output, the manual's name and author are usually printed on
a title page.  Copyright information is usually printed on the back of
the title page.

The title and copyright pages appear in printed manuals, but not in
most other output formats.  Because of this, it is possible to use
several slightly obscure typesetting commands that are not to be used
in the main text.  In addition, this part of the beginning of a
Texinfo file contains the text of the copying permissions that appears
in the printed manual.

@menu
* @code{@@titlepage}::                  Create a title for the printed document.
* @code{@@titlefont @@center @@sp}::      The @code{@@titlefont}, @code{@@center},
                                 and @code{@@sp} commands.
* @code{@@title @@subtitle @@author}::    The @code{@@title}, @code{@@subtitle},
                                 and @code{@@author} commands.
* Copyright::                   How to write the copyright notice and
                                 include copying permissions.
* Heading Generation::          Turn on page headings after the title and
                                 copyright pages.
@end menu

@node @code{@@titlepage}
@subsection @code{@@titlepage}

@anchor{titlepage}@c old name
@cindex Title page
@findex titlepage

Start the material for the title page and following copyright page
with @code{@@titlepage} on a line by itself and end it with
@code{@@end titlepage} on a line by itself.

The @code{@@end titlepage} command starts a new page and turns on page
numbering (@pxref{Heading Generation}).  All the
material that you want to appear on unnumbered pages should be put
between the @code{@@titlepage} and @code{@@end titlepage} commands.
You can force the table of contents to appear there with the
@code{@@setcontentsaftertitlepage} command (@pxref{Contents}).

@findex page@r{, within @code{@@titlepage}}
By using the @code{@@page} command you can force a page break within the
region delineated by the @code{@@titlepage} and @code{@@end titlepage}
commands and thereby create more than one unnumbered page.  This is how
the copyright page is produced.  (The @code{@@titlepage} command might
perhaps have been better named the @code{@@titleandadditionalpages}
command, but that would have been rather long!)

When you write a manual about a computer program, you should write the
version of the program to which the manual applies on the title page.
If the manual changes more frequently than the program or is independent
of it, you should also include an edition number@footnote{We have found
that it is helpful to refer to versions of independent manuals as
`editions' and versions of programs as `versions'; otherwise, we find we
are liable to confuse each other in conversation by referring to both
the documentation and the software with the same words.} for the manual.
This helps readers keep track of which manual is for which version of
the program.  (The `Top' node should also contain this information; see
@ref{The Top Node}.)

Texinfo provides two main methods for creating a title page.  One method
uses the @code{@@titlefont}, @code{@@sp}, and @code{@@center} commands
to generate a title page in which the words on the page are
centered.

The second method uses the @code{@@title}, @code{@@subtitle}, and
@code{@@author} commands to create a title page with black rules under
the title and author lines and the subtitle text set flush to the
right hand side of the page.  With this method, you do not specify any
of the actual formatting of the title page.  You specify the text
you want, and Texinfo does the formatting.

You may use either method, or you may combine them; see the examples in
the sections below.

@findex shorttitlepage
@cindex Bastard title page
@cindex Title page, bastard
For sufficiently simple documents, and for the bastard title page in
traditional book frontmatter, Texinfo also provides a command
@code{@@shorttitlepage} which takes the rest of the line as the title.
The argument is typeset on a page by itself and followed by a blank
page.

@node @code{@@titlefont @@center @@sp}
@subsection @code{@@titlefont}, @code{@@center}, and @code{@@sp}

@anchor{titlefont center sp}@c old name
@findex titlefont
@findex center
@findex sp @r{(titlepage line spacing)}

You can use the @code{@@titlefont}, @code{@@sp}, and @code{@@center}
commands to create a title page for a printed document.  (This is the
first of the two methods for creating a title page in Texinfo.)

Use the @code{@@titlefont} command to select a large font suitable for
the title itself.  You can use @code{@@titlefont} more than once if you
have an especially long title.

For HTML output, each @code{@@titlefont} command produces an
@code{<h1>} heading, but the HTML document @code{<title>} is not
affected.  For that, you must put a @code{@@settitle} command before
the @code{@@titlefont} command (@pxref{@code{@@settitle}}).

@need 700
For example:

@example
@@titlefont@{Texinfo@}
@end example

Use the @code{@@center} command at the beginning of a line to center
the remaining text on that line.  Thus,

@example
@@center @@titlefont@{Texinfo@}
@end example

@noindent
centers the title, which in this example is ``Texinfo'' printed
in the title font.

Use the @code{@@sp} command to insert vertical space.  For example:

@example
@@sp 2
@end example

@noindent
This inserts two blank lines on the printed page.
(@xref{@code{@@sp}}, for more information about the @code{@@sp}
command.)

A template for this method looks like this:

@example
@group
@@titlepage
@@sp 10
@@center @@titlefont@{@var{name-of-manual-when-printed}@}
@@sp 2
@@center @var{subtitle-if-any}
@@sp 2
@@center @var{author}
@dots{}
@@end titlepage
@end group
@end example

The spacing of the example fits an 8.5 by 11 inch manual.

You can in fact use these commands anywhere, not just on a title page,
but since they are not logical markup commands, we don't recommend
them.

@node @code{@@title @@subtitle @@author}
@subsection @code{@@title}, @code{@@subtitle}, and @code{@@author}

@anchor{title subtitle author}@c old name
@findex title
@findex subtitle
@findex author

You can use the @code{@@title}, @code{@@subtitle}, and @code{@@author}
commands to create a title page in which the vertical and horizontal
spacing is done for you automatically.  This contrasts with the method
described in the previous section, in which the @code{@@sp} command is
needed to adjust vertical spacing.

Write the @code{@@title}, @code{@@subtitle}, or @code{@@author}
commands at the beginning of a line followed by the title, subtitle,
or author.  The @code{@@author} command may be used for a quotation in
an @code{@@quotation} block (@pxref{@code{@@quotation}});
except for that, it is an error to use any of these commands outside
of @code{@@titlepage}.

The @code{@@title} command produces a line in which the title is set
flush to the left-hand side of the page in a larger than normal font.
The title is underlined with a black rule.  The title must be given on
a single line in the source file; it will be broken into multiple
lines of output is needed.

For long titles, the @code{@@*} command may be used to specify the
line breaks in long titles if the automatic breaks do not suit.  Such
explicit line breaks are generally reflected in all output formats; if
you only want to specify them for the printed output, use a
conditional (@pxref{Conditionals}).  For example:

@example
@@title This Long Title@@inlinefmt@{tex,@@*@} Is Broken in @@TeX@{@}
@end example

The @code{@@subtitle} command sets subtitles in a normal-sized font
flush to the right-hand side of the page.

The @code{@@author} command sets the names of the author or authors in
a middle-sized font flush to the left-hand side of the page on a line
near the bottom of the title page.  The names are followed by a black
rule that is thinner than the rule that underlines the title.

There are two ways to use the @code{@@author} command: you can write
the name or names on the remaining part of the line that starts with
an @code{@@author} command:

@example
@@author by Jane Smith and John Doe
@end example

@noindent
or you can write the names one above each other by using multiple
@code{@@author} commands:

@example
@group
@@author Jane Smith
@@author John Doe
@end group
@end example

@need 950
A template for this method looks like this:

@example
@group
@@titlepage
@@title @var{name-of-manual-when-printed}
@@subtitle @var{subtitle-if-any}
@@subtitle @var{second-subtitle}
@@author @var{author}
@@page
@dots{}
@@end titlepage
@end group
@end example

@node Copyright
@subsection Copyright Page
@cindex Copyright page
@cindex Printed permissions
@cindex Permissions, printed

By international treaty, the copyright notice for a book must be either
on the title page or on the back of the title page.  When the copyright
notice is on the back of the title page, that page is customarily not
numbered.  Therefore, in Texinfo, the information on the copyright page
should be within @code{@@titlepage} and @code{@@end titlepage}
commands.

@findex vskip @r{@TeX{} vertical skip}
@cindex filll @r{@TeX{} dimension}
Use the @code{@@page} command to cause a page break.  To push the
copyright notice and the other text on the copyright page towards the
bottom of the page, use the following incantation after @code{@@page}:

@example
@@vskip 0pt plus 1filll
@end example

@noindent
The @code{@@vskip} command inserts whitespace in the @TeX{} output; it
is ignored in all other output formats.  The @samp{0pt plus 1filll}
means to put in zero points of mandatory whitespace, and as much
optional whitespace as needed to push the following text to the bottom
of the page.  Note the use of three @samp{l}s in the word
@samp{filll}; this is correct.

To insert the copyright text itself, write @code{@@insertcopying}
next (@pxref{Document Permissions}):

@example
@@insertcopying
@end example

Follow the copying text by the publisher, ISBN numbers, cover art
credits, and other such information.

Here is an example putting all this together:

@example
@@titlepage
@dots{}
@@page
@@vskip 0pt plus 1filll
@@insertcopying

Published by @dots{}

Cover art by @dots{}
@@end titlepage
@end example

We have one more special case to consider: for plain text output, you
must insert the copyright information explicitly if you want it to
appear.  For instance, you could have the following after the copyright
page:

@example
@@ifplaintext
@@insertcopying
@@end ifplaintext
@end example

You could include other title-like information for the plain text
output in the same place.

@node Heading Generation
@subsection Heading Generation

@anchor{end titlepage}@c old name
@cindex Headings, page, begin to appear
@cindex Titlepage end starts headings
@cindex End titlepage starts headings
@cindex Generating page headings

Like all @code{@@end} commands (@pxref{Quotations and Examples}), the
@code{@@end titlepage} command must be written at the beginning of a
line by itself, with only one space between the @code{@@end} and the
@code{titlepage}.  It not only marks the end of the title and
copyright pages, but also causes @TeX{} to start generating page
headings and page numbers.

Texinfo has two standard page heading formats, one for documents
printed on one side of each sheet of paper (single-sided printing),
and the other for documents printed on both sides of each sheet
(double-sided printing).

In full generality, you can control the headings in different ways:

@itemize @bullet
@item
The conventional way is to write a @code{@@setchapternewpage} command
before the title page commands, if required, and then have the
@code{@@end titlepage} command start generating page headings in the
manner desired.

Most documents are formatted with the standard single-sided or
double-sided headings, (sometimes) using @code{@@setchapternewpage
odd} for double-sided printing and (almost always) no
@code{@@setchapternewpage} command for single-sided printing
(@pxref{@code{@@setchapternewpage}}).

@item
Alternatively, you can use the @code{@@headings} command to prevent
page headings from being generated or to start them for either single
or double-sided printing.  Write a @code{@@headings} command
immediately after the @code{@@end titlepage} command.  To turn off
headings, write @code{@@headings off}.  @xref{@code{@@headings}}.

@item
Or, you may specify your own page heading and footing format.
@xref{Headings}.
@end itemize

@node Contents
@section Generating a Table of Contents
@cindex Table of contents
@cindex Contents, table of
@cindex Short table of contents
@findex contents
@findex summarycontents
@findex shortcontents

The @code{@@chapter}, @code{@@section}, and other structuring commands
(@pxref{Chapter Structuring}) supply the information to make up a
table of contents, but they do not cause an actual table to appear in
the manual.  To do this, you must use the @code{@@contents} and/or
@code{@@summarycontents} command(s).

@table @code
@item @@contents
Generates a table of contents in a printed manual, including all
chapters, sections, subsections, etc., as well as appendices and
unnumbered chapters.  Headings generated by @code{@@majorheading},
@code{@@chapheading}, and the other @code{@@@dots{}heading} commands
do not appear in the table of contents (@pxref{Structuring Command
Types}).

@item @@shortcontents
@itemx @@summarycontents
(@code{@@summarycontents} is a synonym for @code{@@shortcontents}.)

Generates a short or summary table of contents that lists only the
chapters, appendices, and unnumbered chapters.  Sections, subsections
and subsubsections are omitted.  Only a long manual needs a short
table of contents in addition to the full table of contents.
@end table

Both contents commands should be written on a line by themselves, and
placed near the beginning of the file, after the @code{@@end
titlepage} (@pxref{@code{@@titlepage}}), before any sectioning
command.  The contents commands automatically generate a chapter-like
heading at the top of the first table of contents page, so don't
include any sectioning command such as @code{@@unnumbered} before
them.

Since an Info file uses menus instead of tables of contents, the Info
formatting commands ignore the contents commands.  But the contents
are included in plain text output (generated by @code{makeinfo
--plaintext}) and in other output formats, such as HTML.

When @code{makeinfo} writes a short table of contents while producing
HTML output, the links in the short table of contents point to
corresponding entries in the full table of contents rather than the text
of the document. The links in the full table of contents point to the
main text of the document.

@node The Top Node
@section The `Top' Node and Master Menu
@cindex Top node
@cindex Node, `Top'

The `Top' node is the node in which a reader enters an Info manual.
As such, it should begin with a brief description of the manual
(including the version number), and end with a master menu for the
whole manual.  Of course you should include any other general
information you feel a reader would find helpful.

@findex top
It is conventional and desirable to write a @code{@@top} sectioning
command line containing the title of the document immediately after
the @code{@@node Top} line (@pxref{@code{@@top} Command}).

The contents of the `Top' node should appear only in the online output;
none of it should appear in printed output, so enclose it between
@code{@@ifnottex} and @code{@@end ifnottex} commands.  (@TeX{} does not
print either an @code{@@node} line or a menu; they appear only in Info;
strictly speaking, you are not required to enclose these parts between
@code{@@ifnottex} and @code{@@end ifnottex}, but it is simplest to do
so.  @xref{Conditionals, , Conditionally Visible Text}.)

@menu
* Top Node Example::
* Master Menu Parts::
@end menu

@node Top Node Example
@subsection Top Node Example

@cindex Top node example

Here is an example of a Top node.

@example
@group
@@ifnottex
@@node Top
@@top Sample Title

This is the text of the top node.
@@end ifnottex
@end group

Additional general information.

@group
@@menu
* First Chapter::
* Second Chapter::
@dots{}
* Index::
@end group
@@end menu
@end example

@node Master Menu Parts
@subsection Parts of a Master Menu
@cindex Master menu
@cindex Menu, master
@cindex Parts of a master menu

A @dfn{master menu} is the main menu.  It is customary to include a
detailed menu listing all the nodes in the document in this menu.

Like any other menu, a master menu is enclosed in @code{@@menu} and
@code{@@end menu} and does not appear in the printed output.

Generally, a master menu is divided into parts.

@itemize @bullet
@item
The first part contains the major nodes in the Texinfo file: the nodes
for the chapters, chapter-like sections, and the appendices.

@item
The second part contains nodes for the indices.

@item
@findex detailmenu
@cindex Detailed menu
The third and subsequent parts contain a listing of the other,
lower-level nodes, often ordered by chapter.  This way, rather than go
through an intermediary menu, an inquirer can go directly to a
particular node when searching for specific information.  These menu
items are not required; add them if you think they are a convenience.
If you do use them, put @code{@@detailmenu} before the first one, and
@code{@@end detailmenu} after the last; otherwise, @code{makeinfo}
will get confused.
@end itemize

Each section in the menu can be introduced by a descriptive line.  So
long as the line does not begin with an asterisk, it will not be
treated as a menu entry.  (@xref{Writing a Menu}, for more
information.)

For example, the master menu for this manual looks like the following
(but has many more entries):

@example
@group
@@menu
* Copying Conditions::  Your rights.
* Overview::            Texinfo in brief.
@dots{}
@end group
@group
* Command and Variable Index::
* General Index::
@end group

@group
@@detailmenu
--- The Detailed Node Listing ---

Overview of Texinfo

* Reporting Bugs:: @dots{}
@dots{}
@end group

@group
Beginning a Texinfo File

* Sample Beginning:: @dots{}
@dots{}
@@end detailmenu
@@end menu
@end group
@end example

@node Global Document Commands
@section Global Document Commands
@cindex Global Document Commands

Besides the basic commands mentioned in the previous sections, here are
additional commands which affect the document as a whole.  They are
generally all given before the Top node, if they are given at all.

@menu
* @code{@@documentdescription}::        Document summary for the HTML output.
* @code{@@setchapternewpage}::          Start chapters on right-hand pages.
* @code{@@headings}::                   An option for turning headings on and off
                                        and double or single sided printing.
* @code{@@paragraphindent}::            Specify paragraph indentation.
* @code{@@firstparagraphindent}::       Suppressing first paragraph indentation.
* @code{@@exampleindent}::              Specify environment indentation.
@end menu

@node @code{@@documentdescription}
@subsection @code{@@documentdescription}: Summary Text
@anchor{documentdescription}@c old name

@cindex Document description
@cindex Description of document
@cindex Summary of document
@cindex Abstract of document
@cindex @code{<meta>} HTML tag, and document description
@findex documentdescription

When producing HTML output for a document, @command{makeinfo} writes a
@samp{<meta>} element in the @samp{<head>} to give some idea of the
content of the document.  By default, this @dfn{description} is the
title of the document, taken from the @code{@@settitle} command
(@pxref{@code{@@settitle}}).  To change this, use the
@code{@@documentdescription} environment, as in:

@example
@@documentdescription
descriptive text.
@@end documentdescription
@end example

@noindent
This will produce the following output in the @samp{<head>} of the HTML:

@example
<meta name=description content="descriptive text.">
@end example

@code{@@documentdescription} must be specified before the first node of
the document.

@node @code{@@setchapternewpage}
@subsection @code{@@setchapternewpage}: Blank Pages Before Chapters

@anchor{setchapternewpage}@c old name
@findex setchapternewpage
@cindex Starting chapters
@cindex Pages, starting odd

In an officially bound book, text is usually printed on both sides of
the paper, chapters start on right-hand pages, and right-hand pages have
odd numbers.  But in short reports, text often is printed only on one
side of the paper.  Also in short reports, chapters sometimes do not
start on new pages, but are printed on the same page as the end of the
preceding chapter, after a small amount of vertical whitespace.

You can use the @code{@@setchapternewpage} command with various
arguments to specify how @TeX{} should start chapters and whether it
should format headers for printing on one or both sides of the paper
(single-sided or double-sided printing).

Write the @code{@@setchapternewpage} command at the beginning of a
line followed by its argument.

For example, you would write the following to cause each chapter to
start on a fresh odd-numbered page:

@example
@@setchapternewpage odd
@end example

You can specify one of three alternatives with the
@code{@@setchapternewpage} command:

@table @asis

@item @code{@@setchapternewpage off}
Cause @TeX{} to typeset a new chapter on the same page as the last
chapter, after skipping some vertical whitespace.  Also, cause @TeX{} to
format page headers for single-sided printing.

@item @code{@@setchapternewpage on}
Cause @TeX{} to start new chapters on new pages and to format page
headers for single-sided printing.  This is the form most often used for
short reports or personal printing. This is the default.

@item @code{@@setchapternewpage odd}
Cause @TeX{} to start new chapters on new, odd-numbered pages
(right-handed pages) and to typeset for double-sided printing.  This is
the form most often used for books and manuals.
@end table

Texinfo does not have a @code{@@setchapternewpage even} command,
because there is no printing tradition of starting chapters or books on
an even-numbered page.

If you don't like the default headers that @code{@@setchapternewpage}
sets, you can explicit control them with the @code{@@headings} command.
@xref{@code{@@headings}}.

At the beginning of a manual or book, pages are not numbered---for
example, the title and copyright pages of a book are not numbered.  By
convention, table of contents and frontmatter pages are numbered with
roman numerals and not in sequence with the rest of the document.

The @code{@@setchapternewpage} has no effect in output formats that do
not have pages, such as Info and HTML.

We recommend not including any @code{@@setchapternewpage} command in
your document source at all, since such desired pagination is not
intrinsic to the document.  For a particular hard copy run, if you
don't want the default output (no blank pages, same headers on all
pages) use the @option{--texinfo} option to @command{texi2dvi} to
specify the output you want.

@node @code{@@headings}
@subsection The @code{@@headings} Command

@anchor{headings on off}@c old name
@findex headings

The @code{@@headings} command is rarely used.  It specifies what kind of
page headings and footings to print on each page.  Usually, this is
controlled by the @code{@@setchapternewpage} command.  You need the
@code{@@headings} command only if the @code{@@setchapternewpage} command
does not do what you want, or if you want to turn off predefined page
headings prior to defining your own.  Write a @code{@@headings} command
immediately after the @code{@@end titlepage} command.

You can use @code{@@headings} as follows:

@table @code
@item @@headings off
Turn off printing of page headings.

@item @@headings single
Turn on page headings appropriate for single-sided printing.

@item @@headings double
Turn on page headings appropriate for double-sided printing.

@item @@headings singleafter
@itemx @@headings doubleafter
Turn on @code{single} or @code{double} headings, respectively, after the
current page is output.

@item @@headings on
Turn on page headings: @code{single} if @samp{@@setchapternewpage
on}, @code{double} otherwise.
@end table

For example, suppose you write @code{@@setchapternewpage off} before the
@code{@@titlepage} command to tell @TeX{} to start a new chapter on the
same page as the end of the last chapter.  This command also causes
@TeX{} to typeset page headers for single-sided printing.  To cause
@TeX{} to typeset for double sided printing, write @code{@@headings
double} after the @code{@@end titlepage} command.

You can stop @TeX{} from generating any page headings at all by
writing @code{@@headings off} on a line of its own immediately after the
line containing the @code{@@end titlepage} command, like this:

@example
@@end titlepage
@@headings off
@end example

@noindent
The @code{@@headings off} command overrides the @code{@@end titlepage}
command, which would otherwise cause @TeX{} to print page headings.

You can also specify your own style of page heading and footing.
@xref{Headings, , Page Headings}, for more information.

@node @code{@@paragraphindent}
@subsection @code{@@paragraphindent}: Controlling Paragraph Indentation

@anchor{paragraphindent}@c old name
@findex paragraphindent
@cindex Indenting paragraphs, control of
@cindex Paragraph indentation control

The Texinfo processors may insert whitespace at the beginning of the
first line of each paragraph, thereby indenting that paragraph.  You can
use the @code{@@paragraphindent} command to specify this indentation.
Write a @code{@@paragraphindent} command at the beginning of a line
followed by either @samp{asis} or a number:

@example
@@paragraphindent @var{indent}
@end example

The indentation is according to the value of @var{indent}:

@table @asis
@item @code{asis}
Do not change the existing indentation (not implemented in @TeX{}).

@item @code{none}
@itemx 0
Omit all indentation.

@item @var{n}
Indent by @var{n} space characters in Info output, by @var{n} ems in
@TeX{}.

@end table

The default value of @var{indent} is 3.  @code{@@paragraphindent} is
ignored for HTML output.

It is best to write the @code{@@paragraphindent} command before the
end-of-header line at the beginning of a Texinfo file, so the region
formatting commands indent paragraphs as specified.  @xref{Start of
Header}.

@node @code{@@firstparagraphindent}
@subsection @code{@@firstparagraphindent}: Indenting After Headings

@anchor{firstparagraphindent}@c old name
@findex firstparagraphindent
@cindex First paragraph, suppressing indentation of
@cindex Suppressing first paragraph indentation
@cindex Preventing first paragraph indentation
@cindex Indenting, suppressing of first paragraph
@cindex Headings, indentation after

As you can see in the present manual, the first paragraph in any
section is not indented by default.  Typographically, indentation is a
paragraph separator, which means that it is unnecessary when a new
section begins.  This indentation is controlled with the
@code{@@firstparagraphindent} command:

@example
@@firstparagraphindent @var{word}
@end example

The first paragraph after a heading is indented according to the value
of @var{word}:

@table @asis
@item @code{none}
Prevents the first paragraph from being indented (default).
This option is ignored by @command{makeinfo} if
@code{@@paragraphindent asis} is in effect.

@item @code{insert}
Include normal paragraph indentation.  This respects the paragraph
indentation set by a @code{@@paragraphindent} command
(@pxref{@code{@@paragraphindent}}).
@end table

@code{@@firstparagraphindent} is ignored for HTML and Docbook output.

It is best to write the @code{@@firstparagraphindent} command before the
end-of-header line at the beginning of a Texinfo file, so the region
formatting commands indent paragraphs as specified.  @xref{Start of
Header}.

@node @code{@@exampleindent}
@subsection @code{@@exampleindent}: Environment Indenting

@anchor{exampleindent}@c old name
@findex exampleindent
@cindex Indenting environments
@cindex Environment indentation
@cindex Example indentation

The Texinfo processors indent each line of @code{@@example} and similar
environments.  You can use the @code{@@exampleindent} command to specify
this indentation.  Write an @code{@@exampleindent} command at the
beginning of a line followed by either @samp{asis} or a number:

@example
@@exampleindent @var{indent}
@end example

The indentation is according to the value of @var{indent}:

@table @asis
@item @code{asis}
Do not change the existing indentation (not implemented in @TeX{}).

@item 0
Omit all indentation.

@item @var{n}
Indent environments by @var{n} space characters in Info output, by
@var{n} ems in @TeX{}.

@end table

The default value of @var{indent} is 5 spaces in Info, and 0.4@dmn{in}
in @TeX{}, which is somewhat less.  (The reduction is to help @TeX{}
fit more characters onto physical lines.)

It is best to write the @code{@@exampleindent} command before the
end-of-header line at the beginning of a Texinfo file, so the region
formatting commands indent paragraphs as specified.  @xref{Start of
Header}.

@node Ending a File
@section Ending a Texinfo File
@cindex Ending a Texinfo file
@cindex Texinfo file ending
@cindex File ending
@findex bye

The end of a Texinfo file should include commands to create indices
(@pxref{Printing Indices & Menus}), and the @code{@@bye} command to mark
the last line to be processed.  For example:

@example
@@node Index
@@unnumbered Index

@@printindex cp

@@bye
@end example

@findex bye
@anchor{File End}
An @code{@@bye} command terminates Texinfo processing.  None of the
formatters process anything following @code{@@bye}; any such text is
completely ignored.  The @code{@@bye} command should be on a line by
itself.

Thus, if you wish, you may follow the @code{@@bye} line with arbitrary
notes.  Also, you may follow the @code{@@bye} line with a local
variables list for Emacs, most typically a @samp{compile-command}
(@pxref{Compile-Command,, Using the Local Variables List}).

@node Nodes
@chapter Nodes
@anchor{node}@anchor{@@node} @c old names

@cindex Node, defined
A @dfn{node} is a region of text that begins at a @code{@@node}
command, and continues until the next @code{@@node} command.
To specify a node, write a @code{@@node} command at the beginning of
a line, and follow it with the name of the node.
Each node contains the discussion of one topic.  Info readers
display one node at a time, and provide commands for the user to move
to related nodes.  The HTML output can be similarly navigated.

Nodes are used as the targets of cross-references.  Cross-references,
such as the one at the end of this sentence, are made with @code{@@xref}
and related commands; see @ref{Cross References}.  Cross-references can
be sprinkled throughout the text, and provide a way to represent links
that do not fit a hierarchical structure.

Normally, you put a node command immediately before each chapter
structuring command---for example, an @code{@@section} or
@code{@@subsection} line.  (@xref{Chapter Structuring}.).
You must do this even if you do not intend to format the file for Info.
This is because @TeX{} uses both @code{@@node} names and
chapter-structuring names in the output for cross-references.  The only
time you are likely to use the chapter structuring commands without also
using nodes is if you are writing a document that contains no cross
references and will only be printed, not transformed into Info, HTML, or
other formats.

@menu
* Texinfo Document Structure::  Double structure of documents.
* Node Names::                  How to choose node names.
* Writing a Node::              How to write an @code{@@node} line.
* Node Line Requirements::      Keep names unique.
* First Node::                  How to write a `Top' node.
* @code{@@top} Command::                How to use the @code{@@top} command.
* Node Menu Illustration::      A diagram, and sample nodes and menus.
* @command{makeinfo} Pointer Creation::   Letting makeinfo determine node pointers.
* Menus::                       Listing subordinate nodes.
@end menu

@node Texinfo Document Structure
@section Texinfo Document Structure
@cindex Texinfo document structure
@cindex Document structure, of Texinfo
@cindex Structure, of Texinfo documents
@cindex Double structure, of Texinfo documents

@anchor{Two Paths}@c node name

Nodes can contain @dfn{menus}, which contain the names of @dfn{child
nodes} within the parent node; for example, a node corresponding to a
chapter would have a menu of the sections in that chapter.  The menus
allow the user to move to the child nodes in a natural way in the online
output.

In addition, nodes contain @dfn{node pointers} that name other nodes.
The `Next' and `Previous' pointers form nodes at the same sectioning
level into a chain.  As you might imagine, the `Next' pointer links to
the next node, and the `Previous' pointer links to the previous node.
Thus, for example, all the nodes that are at the level of sections
within a chapter are linked together, and the order in this chain
is the same as the order of the children in the menu of the parent
chapter.  Each child node records the parent node name as its `Up'
pointer.

@opindex accesskey@r{, in HTML output of nodes}
The Info and HTML output from @command{makeinfo} for each node includes
links to the `Next', `Previous', and `Up' nodes.  The HTML also uses
the @code{accesskey} attribute with the values @samp{n}, @samp{p}, and
@samp{u} respectively.  This allows people using web browsers to
follow the navigation using (typically) @kbd{M-@var{letter}}, e.g.,
@kbd{M-n} for the `Next' node, from anywhere within the node.
Node pointers and menus provide structure for Info files just as
chapters, sections, subsections, and the like provide structure for
printed books.  The two structures are theoretically distinct; in
practice, however, the tree structure of printed books is essentially
always used for the node and menu structure also, as this leads to a
document which is easiest to follow.  @xref{Texinfo Document
Structure}.

Typically, the sectioning structure and the node structure are
completely parallel, with one node for each chapter, section, etc.,
and with the nodes following the same hierarchical arrangement as the
sectioning.  Thus, if a node is at the logical level of a chapter, its
child nodes are at the level of sections; similarly, the child nodes
of sections are at the level of subsections.

Although it is technically possible to create Texinfo documents with
only one structure or the other, or for the two structures not to be
parallel, or for either the sectioning or node structure to be
abnormally formed, etc., this is @emph{not at all recommended}.  To
the best of our knowledge, all the Texinfo manuals currently in
general use do follow the conventional parallel structure.

@node Node Names
@section Choosing Node Names

@cindex Node names, choosing
The name of a node identifies the node.  For all the details of node
names, @pxref{Node Line Requirements}).

@anchor{Node Line Tips}@c previous node name
Here are some suggestions for node names:

@itemize @bullet
@item
Try to pick node names that are informative but short.

In the Info file, the file name, node name, and pointer names are all
inserted on one line, which may run into the right edge of the window.
(This does not cause a problem with Info, but is ugly.)

@item
Try to pick node names that differ from each other near the beginnings
of their names.  This way, it is easy to use automatic name completion in
Info.

@item
Conventionally, node names are capitalized in the same way as section
and chapter titles.  In this manual, initial and significant words are
capitalized; others are not.  In other manuals, just initial words and
proper nouns are capitalized.  Either way is fine; we recommend just
being consistent.
@end itemize

Because node names are used in cross-references, it is not desirable
to casually change them once published.  Such name changes invalidate
references from other manuals, from mail archives, and so on.
@xref{HTML Xref Link Preservation}.

The pointers from a given node enable you to reach other nodes and
consist simply of the names of those nodes.  The pointers are usually
not specified explicitly, as @command{makeinfo} can determine them
(@pxref{@command{makeinfo} Pointer Creation}).

Normally, a node's `Up' pointer contains the name of the node whose
menu mentions that node.  The node's `Next' pointer contains the name
of the node that follows the present node in that menu and its
`Previous' pointer contains the name of the node that precedes it in
that menu.  When a node's `Previous' node is the same as its `Up'
node, both pointers name the same node.

Usually, the first node of a Texinfo file is the `Top' node, and its
`Up' pointer points to the @file{dir} file, which contains the main menu
for all of Info.

@node Writing a Node
@section Writing an @code{@@node} Line
@cindex Writing an @code{@@node} line
@cindex @code{@@node} line writing
@cindex Node line writing

@findex node
The easiest way to write an @code{@@node} line is to write @code{@@node}
at the beginning of a line and then the name of the node, like this:

@example
@@node @var{node-name}
@end example

After you have inserted an @code{@@node} line, you should immediately
write an @@-command for the chapter or section and insert its name.
Next (and this is important!), put in several index entries.  Usually,
you will find at least two and often as many as four or five ways of
referring to the node in the index.  Use them all.  This will make it
much easier for people to find the node.

If you wish, you can ignore @code{@@node} lines altogether in your
first draft and then use the @code{texinfo-insert-node-lines} command
to create @code{@@node} lines for you.  However, we do not recommend
this practice.  It is better to name the node itself at the same time
that you write a segment so you can easily make cross-references.
Useful cross-references are an especially important feature of a good
Texinfo manual.

Even when you explicitly specify all pointers, you cannot write the
nodes in the Texinfo source file in an arbitrary order!  Because
formatters must process the file sequentially, irrespective of node
pointers, you must write the nodes in the order you wish them to
appear in the output.  For Info format one can imagine that the order
may not matter, but it matters for the other formats.

You may optionally follow the node name argument to @code{@@node}
with up to three optional arguments on the rest of the same line,
separating the arguments with commas.  These are the names of the
`Next', `Previous', and `Up' pointers, in that order.  We recommend
omitting them if your Texinfo document is hierarchically organized,
as virtually all are (@pxref{@command{makeinfo} Pointer Creation}).

Any spaces before or after each name on the @code{@@node} line are
ignored.

The template for a fully-written-out node line with `Next', `Previous',
and `Up' pointers looks like this:

@example
@@node @var{node-name}, @var{next}, @var{previous}, @var{up}
@end example

The @var{node-name} argument must be present, but the others are
optional.  If you wish to specify some but not others, just insert
commas as needed, as in: @samp{@@node mynode,,,uppernode}.  However,
we recommend leaving off all the pointers and letting @code{makeinfo}
determine them.

If you are using GNU Emacs, you can use the update node commands
provided by Texinfo mode to insert the names of the pointers; or
(recommended), you can leave the pointers out of the Texinfo file and
let @code{makeinfo} insert node pointers into the Info file it
creates.  (@xref{Texinfo Mode}, and @ref{@command{makeinfo} Pointer
Creation}.)

Alternatively, you can insert the `Next', `Previous', and `Up'
pointers yourself.  If you do this, you may find it helpful to use the
Texinfo mode keyboard command @kbd{C-c C-c n}.  This command inserts
@samp{@@node} and a comment line listing the names of the pointers in
their proper order.  The comment line helps you keep track of which
arguments are for which pointers.  This comment line is especially useful
if you are not familiar with Texinfo.

@node Node Line Requirements
@section @code{@@node} Line Requirements

@cindex Node line requirements
@cindex Restrictions on node names

Names used with @code{@@node} have several requirements:

@itemize @bullet
@item
@cindex Unique node names requirement
@cindex Node names must be unique
All the node names in a single Texinfo file must be unique.

This means, for example, that if you end every chapter with a summary,
you must name each summary node differently.  You cannot just call
them all ``Summary''.  You may, however, duplicate the titles of
chapters, sections, and the like.  Thus you can end each chapter with
a section called ``Summary'', so long as the node names for those
sections are all different.

@item
@cindex Commands in node names
@cindex @@-commands in node names
Node names can contain @@-commands.  The output is generally the
natural result of the command; for example, using @code{@@TeX@{@}} in a
node name results in the @TeX{} logo being output, as it would be in
normal text.  Cross-references should use @code{@@TeX@{@}} just as the
node name does.

For Info and HTML output, especially, it is necessary to expand
commands to some sequence of plain characters; for instance,
@code{@@TeX@{@}} expands to the three letters @samp{TeX} in the Info
node name.  However, cross-references to the node should not take the
``shortcut'' of using @samp{TeX}; stick to the actual node name,
commands and all.

Some commands do not make sense in node names; for instance,
environments (e.g., @code{@@quotation}), commands that read a whole
line as their argument (e.g., @code{@@sp}), and plenty of others.

For the complete list of commands that are allowed, and their
expansion for HTML identifiers and file names, @pxref{HTML Xref
Command Expansion}.  The expansions for Info are generally given with
main the description of the command.

Prior to the Texinfo 5 release in 2013, this feature was supported in
an ad hoc way (the @option{--commands-in-node-names} option to
@command{makeinfo}).  Now it is part of the language.

@item
@cindex Colon in node name
@cindex Comma in node name
@cindex Parentheses in node name
@cindex Period in node name
@cindex Characters, invalid in node name
@cindex Invalid characters in node names
@cindex Node names, invalid characters in
Unfortunately, you cannot reliably use periods, commas, or colons
within a node name; these can confuse the Info reader.  Also, a node
name may not start with a left parenthesis preceding a right
parenthesis, as in @code{(not)allowed}, since this syntax is used to
specify an external manual.  (Perhaps these limitations will be
removed some day.)

@command{makeinfo} warns about such problematic usage in node names,
menu items, and cross-references.  If you don't want to see the
warnings, you can set the customization variable
@code{INFO_SPECIAL_CHARS_WARNING} to @samp{0} (@pxref{Other
Customization Variables}).

Also, if you insist on using these characters in node names (accepting
the resulting substandard Info output), in order not to confuse the
Texinfo processors you must still escape those characters, by using
either special insertions (@pxref{Inserting a Comma}) or @code{@@asis}
(@pxref{@code{@@asis}}).  For example:

@example
@@node foo@@asis@{::@}bar
@end example

As an example of avoiding the special characters, the following is a
section title in this manual:

@smallexample
@@section @@code@{@@@@unnumbered@}, @@code@{@@@@appendix@}: ...
@end smallexample

@noindent
But the corresponding node name lacks the commas and the subtitle:

@smallexample
@@node @code{@@unnumbered @@appendix}
@end smallexample

@cindex Case in node name
@item
Case is significant in node names.

@cindex White space in node name
@cindex Spaces in node name
@item
Spaces before and after names on the @samp{@@node} line are ignored.
Multiple whitespace characters ``inside'' a name are collapsed to a
single space.  For example:

@example
@@node foo bar
@@node  foo bar,
@@node foo bar ,
@@node foo  bar,
@@node  foo  bar ,
@end example

@noindent all define the same node, namely @samp{foo bar}.
In menu entries, this is the name that should be used: no leading or
trailing spaces, and a single internal space.  (For cross-references,
the node name used in the Texinfo sources is automatically normalized
in this way.)

@item
The next/previous/up pointers on @code{@@node} lines must be the names
of nodes.  (It's recommended to leave out these explicit node pointer
names, which automatically avoids any problem here; @pxref{@command{makeinfo}
Pointer Creation}.)
@end itemize

@node First Node
@section The First Node
@cindex Top node is first
@cindex First node

The first node of a Texinfo file is the @dfn{Top} node, except in an
included file (@pxref{Include Files}).  The Top node should contain a
short summary, copying permissions, and a master menu.  @xref{The Top
Node}, for more information on the Top node contents and examples.

Here is a description of the node pointers to be used in the Top node:

@itemize @bullet
@item
@cindex Up node of Top node
@cindex (dir) as Up node of Top node
The Top node (which must be named @samp{top} or @samp{Top}) should have
as its `Up' node the name of a node in another file, where there is a
menu that leads to this file.  Specify the file name in parentheses.

Usually, all Info files are available through a single virtual Info
tree, constructed from multiple directories.  In this case, use
@samp{(dir)} as the parent of the Top node; this specifies the
top-level node in the @file{dir} file, which contains the main menu
for the Info system as a whole.  (Each directory with Info files is
intended to contain a file named @file{dir}.)

That's fine for Info, but for HTML output, one might well want the Up
link from the Top node to go somewhere other than @samp{dir.html}.
For example, for GNU the natural place would be
@url{http://www.gnu.org/manual/} (a web page collecting links to most
GNU manuals), better specified as just @code{/manual/} if the manual
will be installed on @code{www.gnu.org}.  This can be specified with
the @code{TOP_NODE_UP_URL} customization variable (@pxref{HTML
Customization Variables}), as in

@example
$ @kbd{makeinfo --html -c TOP_NODE_UP_URL=/manual/} ...
@end example

All links to @code{(dir)} will be replaced by the given url.

@item
@cindex Prev node of Top node
The `Prev' node of the Top node is usually either omitted or also set
to @file{(dir)}.  Either is fine.

@item
@cindex Next node of Top node
The `Next' node of the Top node should be the first chapter in your
document.

@end itemize

@xref{Installing an Info File}, for more information about installing
an Info file in the @file{info} directory.

It is usually best to leave the pointers off entirely and let the
tools implicitly define them, with this simple result:

@example
@@node Top
@end example

@node @code{@@top} Command
@section The @code{@@top} Sectioning Command

@anchor{top command}@c old name
@anchor{makeinfo top}@c another old name
@anchor{makeinfo top command}@c yet another name
@findex top

The @code{@@top} command is a special sectioning command that you
should only use after a @samp{@@node Top} line at the beginning of a
Texinfo file.  The @code{@@top} command tells the @code{makeinfo}
formatter which node is to be used as the root of the node tree.

It produces the same sort of output as @code{@@unnumbered}
(@pxref{@code{@@unnumbered @@appendix}}).

The @code{@@top} node is conventionally wrapped in an
@code{@@ifnottex} conditional so that it will not appear in @TeX{}
output (@pxref{Conditionals}).
Thus, in practice, a Top node usually looks like this:

@example
@@ifnottex
@@node Top
@@top @var{your-manual-title}

@var{very-high-level-summary}
@@end ifnottex
@end example

@code{@@top} is ignored when raising or lowering sections.  That is,
it is never lowered and nothing can be raised to it
(@pxref{Raise/lower sections}).

@node Node Menu Illustration
@section Node and Menu Illustration

Here is a diagram that illustrates a Texinfo file with three chapters,
each of which contains two sections.

The ``root'' is at the top of the diagram and the ``leaves'' are at
the bottom.  This is how such a diagram is drawn conventionally; it
illustrates an upside-down tree.  For this reason, the root node is
called the `Top' node, and `Up' node pointers carry you closer to the
root.

@example
@group
                         Top
                          |
        -------------------------------------
       |                  |                  |
    Chapter 1          Chapter 2          Chapter 3
       |                  |                  |
    --------           --------           --------
   |        |         |        |         |        |
Section  Section   Section  Section   Section  Section
  1.1      1.2       2.1      2.2       3.1      3.2
@end group
@end example

Using explicit pointers (not recommended, but for shown for purposes
of the example), the fully-written command to start Chapter@tie{}2
would be this:

@example
@group
@@node     Chapter 2,  Chapter 3, Chapter 1, Top
@@comment  node-name,  next,      previous,  up
@end group
@end example

@noindent
This @code{@@node} line says that the name of this node is
``Chapter@tie{}2'', the name of the `Next' node is ``Chapter 3'', the
name of the `Previous' node is ``Chapter@tie{}1'', and the name of the
`Up' node is ``Top''.  You can (and should) omit writing out these
node names if your document is hierarchically organized
(@pxref{@command{makeinfo} Pointer Creation}), but the pointer
relationships still obtain.

@quotation Note
`Next' and `Previous' refer to nodes at the @emph{same hierarchical
level} in the manual, not necessarily to the next node within the
Texinfo file.  In the Texinfo file, the subsequent node may be at a
lower level---a section-level node most often follows a chapter-level
node, for example.  (The `Top' node contains the exception to this
rule.  Since the `Top' node is the only node at that level, `Next'
refers to the first following node, which is almost always a chapter
or chapter-level node.)
@end quotation

To go to Sections 2.1 and 2.2 using Info, you need a menu inside
Chapter 2.  (@xref{Menus}.)  You would write the menu just before the
beginning of Section 2.1, like this:

@example
@group
   @@menu
   * Sect. 2.1::    Description of this section.
   * Sect. 2.2::    Description.
   @@end menu
@end group
@end example

Using explicit pointers, the node for Sect.@: 2.1 is written like this:

@example
@group
@@node     Sect. 2.1, Sect. 2.2, Chapter 2, Chapter 2
@@comment  node-name, next,      previous,  up
@end group
@end example

In Info format, the `Next' and `Previous' pointers of a node usually
lead to other nodes at the same level---from chapter to chapter or
from section to section (sometimes, as shown, the `Previous' pointer
points up); an `Up' pointer usually leads to a node at the level above
(closer to the `Top' node); and a `Menu' leads to nodes at a level
below (closer to `leaves').  (A cross-reference can point to a node at
any level; see @ref{Cross References}.)

A @code{@@node} command and a chapter structuring command are
conventionally used together, in that order, often followed by
indexing commands.  (As shown in the example above, you may follow the
@code{@@node} line with a comment line, e.g., to show which pointer is
which if explicit pointers are used.)  The Texinfo processors use this
construct to determine the relationships between nodes and sectioning
commands.

Here is the beginning of the chapter in this manual called ``Ending a
Texinfo File''.  This shows an @code{@@node} line followed by an
@code{@@chapter} line, and then by indexing lines.

@example
@group
@@node Ending a File
@@chapter Ending a Texinfo File
@@cindex Ending a Texinfo file
@@cindex Texinfo file ending
@@cindex File ending
@end group
@end example

An earlier version of the manual used explicit node pointers.  Here is
the beginning of the same chapter for that case.  This shows an
@code{@@node} line followed by a comment line, a @code{@@chapter}
line, and then by indexing lines.

@example
@group
@@node    Ending a File, Structuring, Beginning a File, Top
@@comment node-name,     next,        previous,         up
@@chapter Ending a Texinfo File
@@cindex Ending a Texinfo file
@dots{}
@end group
@end example

@node @command{makeinfo} Pointer Creation
@section @code{makeinfo} Pointer Creation

@cindex Creating pointers with @code{makeinfo}
@cindex Pointer creation with @code{makeinfo}
@cindex Automatic pointer creation with @code{makeinfo}
@cindex Implicit pointer creation with @code{makeinfo}

The @code{makeinfo} program can automatically determine node pointers
for a hierarchically organized document.  This implicit node pointer
creation feature in @code{makeinfo} relieves you from the need to
update menus and pointers manually or with Texinfo mode commands.
(@xref{Updating Nodes and Menus}.)  We highly recommend taking
advantage of this.

To do so, write your @code{@@node} lines with just the name of the
node:

@example
@@node My Node
@end example

@noindent
You do not need to write out the `Next', `Previous', and `Up'
pointers.

Then, you must write a sectioning command, such as @code{@@chapter}
or @code{@@section}, on the line immediately following each truncated
@code{@@node} line (except that comment lines may intervene).  This is
where it normally goes.

Also, you must write the name of each node (except for the `Top' node)
in a menu that is one or more hierarchical levels above the node's
level.

Finally, you must follow the `Top' @code{@@node} line with a line
beginning with @code{@@top} to mark the top-level node in the file.
@xref{@code{@@top} Command}.

@cindex Detail menu
@findex detailmenu
If you use a detailed menu in your master menu (@pxref{Master Menu
Parts}), mark it with the @code{@@detailmenu @dots{} @@end
detailmenu} environment, or @command{makeinfo} will get confused,
typically about the last and/or first node in the document.

In most cases, you will want to take advantage of this feature and not
redundantly specify node pointers that the programs can determine.
However, Texinfo documents are not required to be organized
hierarchically or in fact to contain sectioning commands at all (for
example, if you never intend the document to be printed), so node
pointers may still be specified explicitly, in full generality.

@node Menus
@section Menus
@cindex Menus
@findex menu

@dfn{Menus} contain pointers to subordinate nodes.  In online output,
you use menus to go to such nodes.  Menus have no effect in printed
manuals and do not appear in them.

@menu
* Writing a Menu::              What is a menu?
* Menu Example::                Two and three part menu entries.
* Menu Location::               Menus go at the ends of nodes.
* Menu Parts::                  A menu entry has three parts.
* Less Cluttered Menu Entry::   Two part menu entry.
* Other Info Files::            How to refer to a different Info file.
@end menu

@node Writing a Menu
@subsection Writing a Menu
@cindex Writing a menu
@cindex Menu writing

A menu consists of a @code{@@menu} command on a line by itself,
followed by menu entry lines or menu comment lines, and then followed
by an @code{@@end menu} command on a line by itself.

A menu looks like this:

@example
@group
@@menu
Larger Units of Text

* Files::                       All about handling files.
* Multiples: Buffers.           Multiple buffers; editing
                                 several files at once.
@@end menu
@end group
@end example

@cindex Spaces, in menus
In a menu, every line that begins with an @w{@samp{* }} is a @dfn{menu
entry}.  (Note the space after the asterisk.)

A line that does not start with an @w{@samp{* }} may also appear in a
menu.  Such a line is not a menu entry but rather a @dfn{menu comment}
line that appears in the Info file.  In the example above, the line
@samp{Larger Units of Text} is such a menu comment line; the two lines
starting with @w{@samp{* }} are menu entries.

@cindex Hierarchical documents, and menus
Technically, menus can carry you to any node, regardless of the
structure of the document; even to nodes in a different Info file.
However, we do not recommend making use of this, because it is hard
for readers to follow.  Also, the @command{makeinfo} implicit pointer
creation feature (@pxref{@command{makeinfo} Pointer Creation}) and GNU
Emacs Texinfo mode updating commands work only to create menus of
subordinate nodes in a hierarchically structured document.  It is much
better to use cross-references to refer to arbitrary nodes.

@cindex Menus, automatically generating
@findex validatemenus
@command{makeinfo} can automatically generate menus in nodes for Info
and HTML output, based on the chapter structure of the document.  To
specify that you want it to do this, place the line
@samp{@@validatemenus off} near the beginning of the document.

In Info, a user selects a node with the @kbd{m} (@code{Info-menu})
command.  The menu entry name is what the user types after the @kbd{m}
command.
@opindex accesskey@r{, in HTML output of menus}
In the HTML output from @command{makeinfo}, the @code{accesskey}
attribute is used with the values @samp{1}@dots{}@samp{9} for the
first nine entries.  This allows people using web browsers to follow
the first menu entries using (typically) @kbd{M-@var{digit}}, e.g.,
@kbd{M-1} for the first entry.

@node Menu Example
@subsection A Menu Example
@cindex Menu example
@cindex Example menu

@c merge with Writing a Menu node?

A menu looks like this in Texinfo:

@example
@group
@@menu
* menu entry name: Node name.   A short description.
* Node name::                   This form is preferred.
@@end menu
@end group
@end example

@need 800
@noindent
This produces:

@example
@group
* menu:

* menu entry name: Node name.   A short description.
* Node name::                   This form is preferred.
@end group
@end example

@need 700
Here is an example as you might see it in a Texinfo file:

@example
@group
@@menu
Larger Units of Text

* Files::                       All about handling files.
* Multiples: Buffers.           Multiple buffers; editing
                                 several files at once.
@@end menu
@end group
@end example

@need 800
@noindent
This produces:

@example
@group
* menu:
Larger Units of Text

* Files::                       All about handling files.
* Multiples: Buffers.           Multiple buffers; editing
                                 several files at once.
@end group
@end example

In this example, the menu has two entries.  @samp{Files} is both a menu
entry name and the name of the node referred to by that name.
@samp{Multiples} is the menu entry name; it refers to the node named
@samp{Buffers}. The line @samp{Larger Units of Text} is a comment; it
appears in the menu, but is not an entry.

Since no file name is specified with either @samp{Files} or
@samp{Buffers}, they must be the names of nodes in the same Info file
(@pxref{Other Info Files, , Referring to Other Info Files}).

@node Menu Location
@subsection Menu Location
@cindex Menu location
@cindex Location of menus

There may be at most one menu in a node.  A menu is conventionally
located at the end of a node, without any regular text or additional
commands between the @code{@@end menu} and the beginning of the next
node.

@cindex Info format, and menus
This convention is useful, since a reader who uses the menu could
easily miss any such text.  Also, any such post-menu text will be
considered part of the menu in Info output (which has no marker for
the end of a menu).  Thus, a line beginning with @samp{* } will likely
be incorrectly handled.

It's usually best if a node with a menu does not contain much text.
If you find yourself with a lot of text before a menu, we generally
recommend moving all but a couple of paragraphs into a new subnode.
Otherwise, it is easy for readers to miss the menu.

@ignore
Years ago, we recommended using a @samp{@@heading} command within an
@code{@@ifinfo} conditional instead of the normal sectioning commands
after a very short node with a menu.  This had the advantage of making
the printed output look better, because there was no very short text
between two headings on the page.  But it does not work with
@command{makeinfo}'s implicit pointer creation, and it also makes the
XML output incorrect, since it does not reflect the true document
structure.  So, we no longer recommend this.
@end ignore

@node Menu Parts
@subsection The Parts of a Menu
@cindex Parts of a menu
@cindex Menu parts
@cindex @code{@@menu} parts

A menu entry has three parts, only the second of which is required:

@enumerate
@item
The menu entry name (optional).

@item
The name of the node (required).

@item
A description of the item (optional).
@end enumerate

The template for a generic menu entry looks like this (but see the
next section for one more possibility):

@example
* @var{menu-entry-name}: @var{node-name}.   @var{description}
@end example

Follow the menu entry name with a single colon, and follow the node
name with tab, comma, newline, or the two characters period and space
(@samp{. }).

The third part of a menu entry is a descriptive phrase or sentence.
Menu entry names and node names are often short; the description
explains to the reader what the node is about.  A useful description
complements the node name rather than repeats it.  The description,
which is optional, can spread over multiple lines; if it does, some
authors prefer to indent the second line while others prefer to align
it with the first (and all others).  It's up to you.  An empty line,
or the next menu entry, ends a description.

Space characters in a menu are preserved as-is in the Info output; this
allows you to format the menu as you wish.  Unfortunately you must type
node names without any extra spaces or some versions of some Info
readers will not find the node (@pxref{Node Line Requirements}).

@command{makeinfo} warns when the text of a menu item (and node names
and cross-references) contains a problematic construct that will
interfere with its parsing in Info.  If you don't want to see the
warnings, you can set the customization variable
@code{INFO_SPECIAL_CHARS_WARNING} to @samp{0} (@pxref{Other
Customization Variables}).

@node Less Cluttered Menu Entry
@subsection Less Cluttered Menu Entry
@cindex Two part menu entry
@cindex Double-colon menu entries
@cindex Menu entries with two colons
@cindex Less cluttered menu entry
@cindex Uncluttered menu entry

When the menu entry name and node name are the same, you can write
the name immediately after the asterisk and space at the beginning of
the line and follow the name with two colons.

@need 800
For example, write

@example
* Name::                        @var{description}
@end example

@need 800
@noindent
instead of

@example
* Name: Name.                   @var{description}
@end example

We recommend using the node name for the menu entry name whenever
possible, since it reduces visual clutter in the menu.

@node Other Info Files
@subsection Referring to Other Info Files
@cindex Referring to other Info files
@cindex Nodes in other Info files
@cindex Other Info files' nodes
@cindex Going to other Info files' nodes
@cindex Info; other files' nodes

You can create a menu entry that enables a reader in Info to go to a
node in another Info file by writing the file name in parentheses just
before the node name.  Some examples:

@example
@group
@@menu
* @var{first-entry-name}:(@var{filename})@var{nodename}.     @var{description}
* (@var{filename})@var{second-node}::                  @var{description}
@@end menu
@end group
@end example

For example, to refer directly to the @samp{Outlining} and
@samp{Rebinding} nodes in the @cite{Emacs Manual}, you could write a
menu like this:

@example
@group
@@menu
* Outlining: (emacs)Outline Mode. The major mode for
                                   editing outlines.
* (emacs)Rebinding::              How to redefine the
                                   meaning of a key.
@@end menu
@end group
@end example

If you do not list the node name, but only name the file, then Info
presumes that you are referring to the `Top' node.  Examples:

@example
@group
* Info: (info).         Documentation browsing system.
* (emacs)::             The extensible, self-documenting
                         text editor.
@end group
@end example

The GNU Emacs Texinfo mode menu updating commands only work with nodes
within the current buffer, so you cannot use them to create menus that
refer to other files.  You must write such menus by hand.

@node Chapter Structuring
@chapter Chapter Structuring
@anchor{Structuring}@c old name
@cindex Chapter structuring
@cindex Structuring of chapters
@cindex Sectioning

Texinfo's @dfn{chapter structuring} commands divide a document into a
hierarchy of chapters, sections, subsections, and subsubsections.  These
commands generate large headings in the text, like the one above.  They
also provide information for generating the table of contents
(@pxref{Contents,, Generating a Table of Contents}).

Normally you put a @code{@@node} command immediately before each
chapter structuring command.  @xref{Nodes}.

@menu
* Tree Structuring::            A manual is like an upside down tree @dots{}
* Structuring Command Types::   How to divide a manual into parts.
* @code{@@chapter}::                    Chapter structuring.
* @code{@@unnumbered @@appendix}::
* @code{@@majorheading @@chapheading}::
* @code{@@section}::
* @code{@@unnumberedsec @@appendixsec @@heading}::
* @code{@@subsection}::
* @code{@@unnumberedsubsec @@appendixsubsec @@subheading}::
* @code{@@subsubsection}::              Commands for the lowest level sections.
* @code{@@part}::                       Collections of chapters.
* Raise/lower sections::        How to change commands' hierarchical level.
@end menu

@node Tree Structuring
@section Tree Structure of Sections
@cindex Tree structuring

A Texinfo file is usually structured like a book with chapters,
sections, subsections, and the like.  This structure can be visualized
as a tree (or rather as an upside-down tree) with the root at the top
and the levels corresponding to chapters, sections, subsection, and
subsubsections.

Here is a diagram that shows a Texinfo file with three chapters, each
with two sections.

@example
@group
                         Top
                          |
        -------------------------------------
       |                  |                  |
    Chapter 1          Chapter 2          Chapter 3
       |                  |                  |
    --------           --------           --------
   |        |         |        |         |        |
Section  Section   Section  Section   Section  Section
  1.1      1.2       2.1      2.2       3.1      3.2

@end group
@end example

In a Texinfo file that has this structure, the beginning of Chapter 2
would be written like this:

@example
@group
@@node    Chapter 2
@@chapter Chapter 2
@end group
@end example

@noindent
For purposes of example, here is how it would be written with
explicit node pointers:

@example
@group
@@node    Chapter 2,  Chapter 3, Chapter 1, Top
@@chapter Chapter 2
@end group
@end example

The chapter structuring commands are described in the sections that
follow; the @code{@@node} command is described in
the previous chapter (@pxref{Nodes}).

@node Structuring Command Types
@section Structuring Command Types

The chapter structuring commands fall into four groups or series, each
of which contains structuring commands corresponding to the
hierarchical levels of chapters, sections, subsections, and
subsubsections.

The four groups of commands are the @code{@@chapter} series, the
@code{@@unnumbered} series, the @code{@@appendix} series, and the
@code{@@heading} series.  Each command produces a title with a
different appearance in the body of the document.  Some of the
commands list their titles in the tables of contents, while others do
not.  Here are the details:

@itemize @bullet
@item
The @code{@@chapter} and @code{@@appendix} series of commands produce
numbered or lettered entries both in the body of a document and in its
table of contents.

@item
The @code{@@unnumbered} series of commands produce unnumbered entries
both in the body of a document and in its table of contents.  The
@code{@@top} command, which has a special use, is a member of this
series (@pxref{@code{@@top} Command}).  An @code{@@unnumbered} section
is a normal part of the document structure.

@item
The @code{@@heading} series of commands produce simple unnumbered
headings that do not appear in a table of contents, are not associated
with nodes, and cannot be cross-referenced.  These heading commands
never start a new page.
@end itemize

When a @code{@@setchapternewpage} command says to do so, the
@code{@@chapter}, @code{@@unnumbered}, and @code{@@appendix} commands
start new pages in the printed manual; the @code{@@heading} commands
do not.  @xref{@code{@@setchapternewpage}}.

Here is a summary:

@tex
{\globaldefs=1 \smallfonts \rm}
@end tex

@multitable @columnfractions .19 .30 .29 .22
@item                        @tab                              @tab                       @tab No new page
@item @i{Numbered}           @tab @i{Unnumbered}               @tab @i{Lettered/numbered} @tab @i{Unnumbered}
@item In contents            @tab In contents                  @tab In contents           @tab Not in contents
@item                        @tab @code{@@top}                 @tab                       @tab @code{@@majorheading}
@item @code{@@chapter}       @tab @code{@@unnumbered}          @tab @code{@@appendix} @tab @code{@@chapheading}
@item @code{@@section}       @tab @code{@@unnumberedsec}       @tab @code{@@appendixsec} @tab @code{@@heading}
@item @code{@@subsection}    @tab @code{@@unnumberedsubsec}    @tab @code{@@appendixsubsec} @tab @code{@@subheading}
@item @code{@@subsubsection} @tab @code{@@unnumberedsubsubsec} @tab @code{@@appendixsubsubsec} @tab @code{@@subsubheading}
@end multitable
@tex
{\globaldefs=1 \textfonts \rm}
@end tex

@node @code{@@chapter}
@section @code{@@chapter}: Chapter Structuring

@anchor{chapter}@c old name
@findex chapter

@code{@@chapter} identifies a chapter in the document--the highest
level of the normal document structuring hierarchy.  Write the command
at the beginning of a line and follow it on the same line by the title
of the chapter.  The chapter is numbered automatically, starting
from@tie{}1.

For example, the present chapter in this manual is entitled
``@code{@@chapter}: Chapter Structuring''; the @code{@@chapter} line
looks like this:

@example
@@chapter @@code@{@@@@chapter@}: Chapter Structuring
@end example

In @TeX{}, the @code{@@chapter} command produces a chapter heading in
the document.

In Info and plain text output, the @code{@@chapter} command causes the
title to appear on a line by itself, with a line of asterisks inserted
underneath.  So, the above example produces the following output:

@example
@group
5 Chapter Structuring
*********************
@end group
@end example

In HTML, the @code{@@chapter} command produces an @code{<h2>}-level
header by default (controlled by the @code{CHAPTER_HEADER_LEVEL}
customization variable, @pxref{Other Customization Variables}).

In the XML and Docbook output, a @code{<chapter>} element is produced
that includes all the following sections, up to the next chapter.

@node @code{@@unnumbered @@appendix}
@section @code{@@unnumbered}, @code{@@appendix}: Chapters with Other Labeling

@anchor{unnumbered & appendix}@c old name
@findex unnumbered
@findex appendix

Use the @code{@@unnumbered} command to start a chapter-level element
that appears without chapter numbers of any kind.  Use the
@code{@@appendix} command to start an appendix that is labeled by
letter (`A', `B', @dots{}) instead of by number; appendices are also
at the chapter level of structuring.

Write an @code{@@appendix} or @code{@@unnumbered} command at the
beginning of a line and follow it on the same line by the title,
just as with @code{@@chapter}.

@findex centerchap
Texinfo also provides a command @code{@@centerchap}, which is analogous
to @code{@@unnumbered}, but centers its argument in the printed and HTML
outputs.  This kind of stylistic choice is not usually offered by
Texinfo.  It may be suitable for short documents.
@c but the Hacker's Dictionary wanted it, before they quit Texinfo.

@cindex Docbook and prefatory sections
@cindex Preface, etc., and Docbook
With @code{@@unnumbered}, if the name of the associated node is one of
these English words (case-insensitive):

@example
Acknowledgements  Colophon  Dedication  Preface
@end example

@cindex @code{<acknowledgements>} Docbook tag
@cindex @code{<colophon>} Docbook tag
@cindex @code{<dedication>} Docbook tag
@cindex @code{<preface>} Docbook tag
@cindex @code{<chapter>} Docbook tag
@cindex @code{<title>} Docbook tag
@noindent then the Docbook output uses corresponding special tags
(@code{<preface>}, etc.)@: instead of the default @code{<chapter>}.
The argument to @code{@@unnumbered} itself can be anything, and is
output as the following @code{<title>} text as usual.

@node @code{@@majorheading @@chapheading}
@section @code{@@majorheading}, @code{@@chapheading}: Chapter-level Headings

@anchor{majorheading & chapheading}@c old name
@findex majorheading
@findex chapheading

The @code{@@majorheading} and @code{@@chapheading} commands produce
chapter-like headings in the body of a document.

However, neither command produces an entry in the table of contents,
and neither command causes @TeX{} to start a new page in a printed
manual.

In @TeX{}, a @code{@@majorheading} command generates a larger vertical
whitespace before the heading than a @code{@@chapheading} command but
is otherwise the same.

In Info and plain text, the @code{@@majorheading} and
@code{@@chapheading} commands produce the same output as
@code{@@chapter}: the title is printed on a line by itself with a line
of asterisks underneath.  Similarly for HTML@.  The only difference is
the lack of numbering and the lack of any association with nodes.
@xref{@code{@@chapter}}.

@node @code{@@section}
@section @code{@@section}: Sections Below Chapters

@anchor{section}@c old name
@findex section

An @code{@@section} command identifies a section within a chapter
unit, whether created with @code{@@chapter}, @code{@@unnumbered}, or
@code{@@appendix}, following the numbering scheme of the chapter-level
command.  Thus, within a @code{@@chapter} chapter numbered `1', the
sections are numbered `1.1', `1.2', etc.; within an @code{@@appendix}
``chapter'' labeled `A', the sections are numbered `A.1', `A.2', etc.;
within an @code{@@unnumbered} chapter, the section gets no number.
The output is underlined with @samp{=} in Info and plain text.

To make a section, write the @code{@@section} command at the
beginning of a line and follow it on the same line by the section
title.  For example,

@example
@@section This is a section
@end example

@noindent
might produce the following in Info:

@example
@group
5.7 This is a section
=====================
@end group
@end example

Section titles are listed in the table of contents.

The @TeX{}, HTML, Docbook, and XML output is all analogous to the
chapter-level output, just ``one level down''; @pxref{@code{@@chapter}}.

@node @code{@@unnumberedsec @@appendixsec @@heading}
@section @code{@@unnumberedsec}, @code{@@appendixsec}, @code{@@heading}

@anchor{unnumberedsec appendixsec heading}@c old name
@findex unnumberedsec
@findex appendixsec
@findex heading

The @code{@@unnumberedsec}, @code{@@appendixsec}, and @code{@@heading}
commands are, respectively, the unnumbered, appendix-like, and
heading-like equivalents of the @code{@@section} command (see the
previous section).

@code{@@unnumberedsec} and @code{@@appendixsec} do not need to be used
in ordinary circumstances, because @code{@@section} may also be used
within @code{@@unnumbered} and @code{@@appendix} chapters; again, see
the previous section.

@table @code
@item @@unnumberedsec
The @code{@@unnumberedsec} command may be used within an unnumbered
chapter or within a regular chapter or appendix to produce an
unnumbered section.

@item @@appendixsec
@itemx @@appendixsection
@findex appendixsection
@findex appendixsec
@code{@@appendixsection} is a longer spelling of the
@code{@@appendixsec} command; the two are synonymous.

Conventionally, the @code{@@appendixsec} or @code{@@appendixsection}
command is used only within appendices.

@item @@heading
You may use the @code{@@heading} command (almost) anywhere for a
section-style heading that will not appear in the table of contents.
The @code{@@heading}-series commands can appear inside most
environments, for example, though pathological and useless locations
such as inside @code{@@titlepage}, as an argument to another command,
etc., are not allowed.

@end table

@node @code{@@subsection}
@section @code{@@subsection}: Subsections Below Sections

@anchor{subsection}@c old name
@findex subsection

Subsections are to sections as sections are to chapters;
@pxref{@code{@@section}}.  In Info and plain text, subsection titles
are underlined with @samp{-}.  For example,

@example
@@subsection This is a subsection
@end example

@noindent
might produce

@example
@group
1.2.3 This is a subsection
--------------------------
@end group
@end example

Subsection titles are listed in the table of contents.

The @TeX{}, HTML, Docbook, and XML output is all analogous to the
chapter-level output, just ``two levels down'';
@pxref{@code{@@chapter}}.

@node @code{@@unnumberedsubsec @@appendixsubsec @@subheading}
@section The @code{@@subsection}-like Commands

@anchor{unnumberedsubsec appendixsubsec subheading}@c old name
@findex unnumberedsubsec
@findex appendixsubsec
@findex subheading
@cindex Subsection-like commands

The @code{@@unnumberedsubsec}, @code{@@appendixsubsec}, and
@code{@@subheading} commands are, respectively, the unnumbered,
appendix-like, and heading-like equivalents of the @code{@@subsection}
command.  (@xref{@code{@@subsection}}.)

@code{@@unnumberedsubsec} and @code{@@appendixsubsec} do not need to
be used in ordinary circumstances, because @code{@@subsection} may
also be used within sections of @code{@@unnumbered} and
@code{@@appendix} chapters (@pxref{@code{@@section}}).

An @code{@@subheading} command produces a heading like that of a
subsection except that it is not numbered and does not appear in the
table of contents.  Similarly, an @code{@@unnumberedsubsec} command
produces an unnumbered heading like that of a subsection and an
@code{@@appendixsubsec} command produces a subsection-like heading
labeled with a letter and numbers; both of these commands produce
headings that appear in the table of contents.  In Info and plain
text, the @code{@@subsection}-like commands generate a title
underlined with hyphens.

@node @code{@@subsubsection}
@section @code{@@subsection} and Other Subsub Commands

@anchor{subsubsection}@c old name
@findex subsubsection
@findex unnumberedsubsubsec
@findex appendixsubsubsec
@findex subsubheading
@cindex Subsub sectioning commands

The fourth and lowest level sectioning commands in Texinfo are the
`subsub' commands.  They are:

@table @code
@item @@subsubsection
Subsubsections are to subsections as subsections are to sections.
(@xref{@code{@@subsection}}.)  Subsubsection titles appear in the
table of contents.

@item @@unnumberedsubsubsec
Unnumbered subsubsection titles appear in the table of contents,
but lack numbers.  Otherwise, unnumbered subsubsections are the same
as subsubsections.

@item @@appendixsubsubsec
Conventionally, appendix commands are used only for appendices and are
lettered and numbered appropriately.  They also appear in the table
of contents.

@item @@subsubheading
The @code{@@subsubheading} command may be used anywhere that you want
a small heading that will not appear in the table of contents.
@end table

As with subsections, @code{@@unnumberedsubsubsec} and
@code{@@appendixsubsubsec} do not need to be used in ordinary
circumstances, because @code{@@subsubsection} may also be used within
subsections of @code{@@unnumbered} and @code{@@appendix} chapters
(@pxref{@code{@@section}}).

In Info, `subsub' titles are underlined with periods.  For example,

@example
@@subsubsection This is a subsubsection
@end example

@noindent
might produce

@example
@group
1.2.3.4 This is a subsubsection
...............................
@end group
@end example

The @TeX{}, HTML, Docbook, and XML output is all analogous to the
chapter-level output, just ``three levels down''; @pxref{@code{@@chapter}}.

@node @code{@@part}
@section @code{@@part}: Groups of Chapters
@findex part
@cindex Part pages

The final sectioning command is @code{@@part}, to mark a @dfn{part} of
a manual, that is, a group of chapters or (rarely) appendices.  This
behaves quite differently from the other sectioning commands, to fit
with the way such ``parts'' are conventionally used in books.

No @code{@@node} command is associated with @code{@@part}.  Just write
the command on a line by itself, including the part title, at the
place in the document you want to mark off as starting that part.  For
example:

@example
@@part Part I:@@* The beginning
@end example

As can be inferred from this example, no automatic numbering or
labeling of the @code{@@part} text is done.  The text is taken as-is.

Because parts are not associated with nodes, no general text can
follow the @code{@@part} line.  To produce the intended output, it
must be followed by a chapter-level command (including its node).
Thus, to continue the example:

@example
@@part Part I:@@* The beginning

@@node Introduction
@@chapter Introduction
...
@end example

In the @TeX{} output, the @code{@@part} text is included in both the
normal and short tables of contents (@pxref{Contents}), without a page
number (since that is the normal convention).  In addition, a ``part
page'' is output in the body of the document, with just the
@code{@@part} text.  In the example above, the @code{@@*} causes a
line break on the part page (but is replaced with a space in the
tables of contents).  This part page is always forced to be on an odd
(right-hand) page, regardless of the chapter pagination
(@pxref{@code{@@setchapternewpage}}).

In the HTML output, the @code{@@part} text is similarly included in
the tables of contents, and a heading is included in the main document
text, as part of the following chapter or appendix node.

In the XML and Docbook output, the @code{<part>} element includes all
the following chapters, up to the next @code{<part>}.  A @code{<part>}
containing chapters is also closed at an appendix.

In the Info and plain text output, @code{@@part} has no effect.

@code{@@part} is ignored when raising or lowering sections (see next
section).  That is, it is never lowered and nothing can be raised to it.

@node Raise/lower sections
@section Raise/lower Sections: @code{@@raisesections} and @code{@@lowersections}
@findex raisesections
@findex lowersections
@cindex Raising and lowering sections
@cindex Lowering and raising sections
@cindex Sections, raising and lowering

The @code{@@raisesections} and @code{@@lowersections} commands
implicitly raise and lower the hierarchical level of following
chapters, sections and the other sectioning commands (excluding parts).

That is, the @code{@@raisesections} command changes sections to
chapters, subsections to sections, and so on.  Conversely, the
@code{@@lowersections} command changes chapters to sections, sections
to subsections, and so on.  Thus, a @code{@@lowersections} command
cancels a @code{@@raisesections} command, and vice versa.

@cindex Include files, and section levels
You can use @code{@@lowersections} to include text written as an outer
or standalone Texinfo file in another Texinfo file as an inner,
included file (@pxref{Include Files}).  Typical usage looks like this:

@example
@@lowersections
@@include somefile.texi
@@raisesections
@end example

@noindent (Without the @code{@@raisesections}, all the subsequent
sections in the main file would also be lowered.)

If the included file being lowered has a @code{@@top} node, you'll
need to conditionalize its inclusion with a flag (@pxref{@code{@@set
@@value}}).

As a practical matter, you generally only want to raise or lower large
chunks, usually in external files as shown above.  The final result has
to have menus that take the raising and lowering into account, so you
cannot just arbitrarily sprinkle @code{@@raisesections} and
@code{@@lowersections} commands throughout the document.

Repeated use of the commands continues to raise or lower the
hierarchical level a step at a time.  An attempt to raise above
`chapter' reproduces chapter commands; an attempt to lower below
`subsubsection' reproduces subsubsection commands.  Also, lowered
subsubsections and raised chapters will not work with
@command{makeinfo}'s feature of implicitly determining node pointers,
since the menu structure cannot be represented correctly.

Write each @code{@@raisesections} and @code{@@lowersections} command
on a line of its own.

@node Cross References
@chapter Cross-references
@cindex Making cross-references
@cindex Cross-references
@cindex References

@dfn{Cross-references} are used to refer the reader to other parts of the
same or different Texinfo files.

@menu
* References::                  What cross-references are for.
* Cross Reference Commands::    A summary of the different commands.
* Cross Reference Parts::       A cross-reference has several parts.
* @code{@@xref}::                       Begin a reference with `See' @dots{}
* Referring to a Manual as a Whole::   Refer to an entire manual.
* @code{@@ref}::                        A reference for the last part of a sentence.
* @code{@@pxref}::                      How to write a parenthetical cross-reference.
* @code{@@anchor}::                     Defining arbitrary cross-reference targets
* @code{@@inforef}::                    How to refer to an Info-only file.
* @code{@@url}::                        How to refer to a uniform resource locator.
* @code{@@cite}::                       How to refer to books not in the Info system.
@end menu

@node References
@section What References Are For

Often, but not always, a printed document should be designed so that
it can be read sequentially.  People tire of flipping back and forth
to find information that should be presented to them as they need
it.

However, in any document, some information will be too detailed for
the current context, or incidental to it; use cross-references to
provide access to such information.  Also, an online help system or a
reference manual is not like a novel; few read such documents in
sequence from beginning to end.  Instead, people look up what they
need.  For this reason, such creations should contain many cross
references to help readers find other information that they may not
have read.

In a printed manual, a cross-reference results in a page reference,
unless it is to another manual altogether, in which case the
cross-reference names that manual.  In Info, a cross-reference results
in an entry that you can follow using the Info @samp{f} command.
(@xref{Help-Xref,, Following cross-references, info, Info}.)  In HTML, a
cross-reference results in an hyperlink.

The various cross-reference commands use nodes (or anchors,
@pxref{@code{@@anchor}}) to define cross-reference locations.
@TeX{} needs nodes to define cross-reference locations.  When @TeX{}
generates a DVI file, it records each node's page number and uses the
page numbers in making references.  Thus, even if you are writing a
manual that will only be printed, and not used online, you must
nonetheless write @code{@@node} lines in order to name the places to
which you make cross-references.

@need 800
@node Cross Reference Commands
@section Different Cross-reference Commands
@cindex Different cross-reference commands

There are three different cross-reference commands:

@table @code
@item @@xref
Used to start a sentence in the printed manual and in HTML with
@w{`See @dots{}'} or an Info cross-reference saying @samp{*Note
@var{name}: @var{node}.}.

@item @@ref
Used within or, more often, at the end of a sentence; produces just
the reference in the printed manual and in HTML without the preceding
`See' (same as @code{@@xref} for Info).

@item @@pxref
Used within parentheses, at the end of a sentence, or otherwise before
punctuation, to make a reference.  Its output starts with a lowercase
`see' in the printed manual and in HTML, and a lowercase @samp{*note}
in Info.  (@samp{p} is for `parenthesis'.)
@end table

Additionally, there are commands to produce references to documents
outside the Texinfo system.  The @code{@@cite} command is used
to make references to books and manuals.  @code{@@url} produces
a @acronym{URL}, for example a reference to a page on the World
Wide Web.  @code{@@inforef} is used to make a reference to an Info
file for which there is no printed manual.

@node Cross Reference Parts
@section Parts of a Cross-reference
@cindex Cross-reference parts
@cindex Parts of a cross-reference
@anchor{Reference Syntax} @c merged node

A cross-reference command requires only one argument, which is
the name of the node to which it refers.  Here is a simple example:

@example
@@xref@{Node name@}.
@end example

@noindent
In Info output, this produces

@example
*Note Node name::.
@end example

@noindent
In a printed manual, the output is

@quotation
See Section @var{nnn} [Node name], page @var{ppp}.
@end quotation

A cross-reference command may contain up to four additional arguments.
By using these arguments, you can provide a cross-reference name,
a topic description or section title for the printed output, the name
of a different manual file, and the name of a different printed manual.
To refer to another manual as a whole, the manual file and/or the name
of the printed manual are the only required arguments (@pxref{Referring
to a Manual as a Whole}).

@need 700
Here is an example of a full five-part cross-reference:

@example
@group
@@xref@{Node name, Online Label, Printed Label,
info-file-name, A Printed Manual@}, for details.
@end group
@end example

@noindent
which produces

@example
*Note Online Label: (info-file-name)Node name,
for details.
@end example

@noindent
in Info and

@quotation
See section ``Printed Label'' in @i{A Printed Manual}, for details.
@end quotation

@noindent
in a printed book.

The five possible arguments for a cross-reference are:

@enumerate
@item
The node or anchor name (required, except for reference to whole
manuals).  This is the location to which the cross-reference takes
you.  In a printed document, the location of the node provides the
page reference only for references within the same document.
Use @code{@@node} to define the node (@pxref{Writing a Node}), or
@code{@@anchor} (@pxref{@code{@@anchor}}).

Write a node name in a cross-reference in exactly the same way as in
the @code{@@node} line, including the same capitalization; otherwise, the
formatters may not find the reference.

@item
A label for online output.  It is usually omitted; then
the topic description (third argument) is used if it was specified;
if that was omitted as well, the node name is used.

@item
A label for printed output.  Often, this is the title or topic of the
section.  This is used as the name of the reference in the printed
manual.  If omitted, the node name is used.

@item
The name of the manual file in which the reference is located, if it is
different from the current file.  This name is used both for Info and
HTML.

@item
The name of a printed manual from a different Texinfo file.
@end enumerate

The template for a full five argument cross-reference looks like
this:

@example
@group
@@xref@{@var{node-name}, @var{online-label}, @var{printed-label},
@var{info-file-name}, @var{printed-manual-title}@}
@end group
@end example

Whitespace before and after the commas separating these arguments is
ignored.  To include a comma in one of the arguments, use
@code{@@comma@{@}} (@pxref{Inserting a Comma}).

@cindex Comma after cross-reference
When processing with TeX, a comma is automatically inserted after the
page number for cross-references to within the same manual, unless the
closing brace of the argument is followed by non-whitespace (such as a
comma or period).  This gives you the choice of whether to have a comma
there in Info or HTML output.  For example,

@example
@@xref@{Another Section@} for more information
@end example

@noindent produces
@w{`See Another Section, page @var{ppp}, for more information'} in the
printed output, and
@w{@samp{*Note Another Section:: for more information}} in the Info
output.

If an unwanted comma is added, follow the argument
with a command such as @samp{@@:}.  For example,
@w{@samp{@@xref@{Hurricanes@}@@: --- for the details}} produces

@quotation
See Hurricanes, page @var{ppp} --- for the details
@end quotation

@noindent instead of
@w{`See Hurricanes, page @var{ppp}, --- for the details'}.

Cross-references with one, two, three, four, and five arguments are
described separately following the description of @code{@@xref}.

@command{makeinfo} warns when the text of a cross-reference (and node
names and menu items) contains a problematic construct that will
interfere with its parsing in Info.  If you don't want to see the
warnings, you can set the customization variable
@code{INFO_SPECIAL_CHARS_WARNING} to @samp{0} (@pxref{Other
Customization Variables}).

@node @code{@@xref}
@section @code{@@xref}

@anchor{xref}@c old name
@findex xref
@cindex Cross-references using @code{@@xref}
@cindex References using @code{@@xref}

The @code{@@xref} command generates a cross-reference for the
beginning of a sentence.

@menu
* One Argument::                @code{@@xref} with one argument.
* Two Arguments::               @code{@@xref} with two arguments.
* Three Arguments::             @code{@@xref} with three arguments.
* Four and Five Arguments::     @code{@@xref} with four and five arguments.
@end menu

@node One Argument
@subsection @code{@@xref} with One Argument
@cindex One-argument form of cross-references

The simplest form of @code{@@xref} takes one argument, the name of
another node in the same Texinfo file.

@need 700
@noindent
For example,

@example
@@xref@{Tropical Storms@}.
@end example

@noindent
produces

@example
*Note Tropical Storms::.
@end example

@noindent
in Info and

@quotation
See Section 3.1 [Tropical Storms], page 24.
@end quotation

@noindent
in a printed manual.

@node Two Arguments
@subsection @code{@@xref} with Two Arguments
@cindex Two-argument form of cross-references

With two arguments, the second is used as a label for the online output.

@need 750
@noindent
The template is like this:

@example
@@xref@{@var{node-name}, @var{online-label}@}.
@end example

@need 700
@noindent
For example,

@example
@@xref@{Electrical Effects, Lightning@}.
@end example

@noindent
produces:

@example
*Note Lightning: Electrical Effects.
@end example

@noindent
in Info and

@quotation
See Section 5.2 [Electrical Effects], page 57.
@end quotation

@noindent
in a printed manual, where the node name is printed.

The second argument to cross-references must observe some of the
restrictions for node names (@pxref{Node Line Requirements}).  The
most common issue is that colons cannot be used, since that interferes
with the parsing of the Info file.

@node Three Arguments
@subsection @code{@@xref} with Three Arguments
@cindex Three-argument form of cross-references

A third argument replaces the node name in the @TeX{} output.  The third
argument should be the name of the section in the printed output, or
else state the topic discussed by that section.

@need 750
@noindent
The template is like this:

@example
@group
@@xref@{@var{node-name}, @var{online-label}, @var{printed-label}@}.
@end group
@end example

@need 700
@noindent
For example,

@example
@group
@@xref@{Electrical Effects, Lightning, Thunder and Lightning@},
for details.
@end group
@end example

@noindent
produces

@example
*Note Lightning: Electrical Effects, for details.
@end example

@noindent
in Info and

@quotation
See Section 5.2 [Thunder and Lightning], page 57, for details.
@end quotation

@noindent
in a printed manual.

If a third argument is given and the second one is empty, then the
third argument serves for both.  (Note how two commas, side by side, mark
the empty second argument.)

@example
@group
@@xref@{Electrical Effects, , Thunder and Lightning@},
for details.
@end group
@end example

@noindent
produces

@example
*Note Thunder and Lightning: Electrical Effects, for details.
@end example

@noindent
in Info and

@quotation
See Section 5.2 [Thunder and Lightning], page 57, for details.
@end quotation

@noindent
in a printed manual.

The third argument to cross-references must observe some of the
restrictions for node names (@pxref{Node Line Requirements}).  The
most common issue is that colons cannot be used, since that interferes
with the parsing of the Info file.

As a practical matter, it is often best to write cross-references with
just the first argument if the node name and the section title are the
same (or nearly so), and with the first and third arguments only if the
node name and title are different.

@findex xrefautomaticsectiontitle
Texinfo offers a setting to use the section title instead of node
names by default in cross-references (an explicitly specified third
argument still takes precedence):

@example
@@xrefautomaticsectiontitle on
@end example

Typically this line would be given near the beginning of the document
and used for the whole manual.  But you can turn it off if you want
(@code{@@xrefautomaticsectiontitle off}), for example, if you're
including some other sub-document that doesn't have suitable section
names.

@node Four and Five Arguments
@subsection @code{@@xref} with Four and Five Arguments
@cindex Four- and five argument forms of cross-references

In a cross-reference, a fourth argument specifies the name of another
Info file, different from the file in which the reference appears, and
a fifth argument specifies its title as a printed manual.

@need 800
@noindent
The full template is:

@example
@group
@@xref@{@var{node-name}, @var{online-label}, @var{printed-label},
@var{info-file-name}, @var{printed-manual-title}@}.
@end group
@end example

@need 700
@noindent
For example,

@example
@@xref@{Electrical Effects, Lightning, Thunder and Lightning,
weather, An Introduction to Meteorology@}.
@end example

@noindent
produces this output in Info:

@example
*Note Lightning: (weather)Electrical Effects.
@end example

@noindent
As you can see, the name of the Info file is enclosed in parentheses
and precedes the name of the node.

@noindent
In a printed manual, the reference looks like this:

@quotation
See section ``Thunder and Lightning'' in @cite{An Introduction to
Meteorology}.
@end quotation

@noindent
The title of the printed manual is typeset like @code{@@cite}; and the
reference lacks a page number since @TeX{} cannot know to which page a
reference refers when that reference is to another manual.

Next case: often, you will leave out the second argument when you use
the long version of @code{@@xref}.  In this case, the third argument,
the topic description, will be used as the cross-reference name in
Info.  For example,

@example
@@xref@{Electrical Effects, , Thunder and Lightning,
weather, An Introduction to Meteorology@}.
@end example

@noindent
produces

@example
@group
*Note Thunder and Lightning: (weather)Electrical Effects.
@end group
@end example

@noindent
in Info and

@quotation
See section ``Thunder and Lightning'' in @cite{An Introduction to
Meteorology}.
@end quotation

@noindent
in a printed manual.

Next case: If the node name and the section title are the same in the
other manual, you may also leave out the section title.  In this case,
the node name is used in both instances.  For example,

@example
@@xref@{Electrical Effects,,,
weather, An Introduction to Meteorology@}.
@end example

@noindent
produces

@example
@group
*Note (weather)Electrical Effects::.
@end group
@end example

@noindent
in Info and

@quotation
See section ``Electrical Effects'' in @cite{An Introduction to
Meteorology}.
@end quotation

@noindent
in a printed manual.

A very unusual case: you may want to refer to another manual file that
is within a single printed manual---when multiple Texinfo files are
incorporated into the same @TeX{} run but can create separate Info or
HTML output files.  In this case, you need to specify only the fourth
argument, and not the fifth.

Finally, it's also allowed to leave out all the arguments
@emph{except} the fourth and fifth, to refer to another manual as a
whole.  See the next section.

@node Referring to a Manual as a Whole
@section Referring to a Manual as a Whole
@cindex Manual, referring to as a whole
@cindex Referring to an entire manual
@anchor{Top Node Naming} @c old name

Ordinarily, you must always name a node in a cross-reference.
However, it's not unusual to want to refer to another manual as a
whole, rather than a particular section within it.  In this case,
giving any section name is an unnecessary distraction.

So, with cross-references to other manuals (@pxref{Four and Five
Arguments}), if the first argument is either @samp{Top} (capitalized
just that way) or omitted entirely, and the third argument is omitted,
the printed output includes no node or section name.  (The Info output
includes @samp{Top} if it was given.)  For example,

@example
@@xref@{Top,,, make, The GNU Make Manual@}.
@end example

@noindent produces

@example
@group
*Note (make)Top::.
@end group
@end example

@noindent and

@quotation
See @cite{The GNU Make Manual}.
@end quotation

@noindent
Info readers will go to the Top node of the manual whether
or not the `Top' node is explicitly specified.

It's also possible (and is historical practice) to refer to a whole
manual by specifying the `Top' node and an appropriate entry for the
third argument to the @code{@@xref} command.  Using this idiom, to
make a cross-reference to @cite{The GNU Make Manual}, you would write:

@example
@@xref@{Top,, Overview, make, The GNU Make Manual@}.
@end example

@noindent
which produces

@example
*Note Overview: (make)Top.
@end example

@noindent
in Info and

@quotation
See section ``Overview'' in @cite{The GNU Make Manual}.
@end quotation

@noindent
in a printed manual.

In this example, @samp{Top} is the name of the first node, and
@samp{Overview} is the name of the first section of the manual.  There
is no widely-used convention for naming the first section in a printed
manual, this is just what the Make manual happens to use.  This
arbitrariness of the first name is a principal reason why omitting the
third argument in whole-manual cross-references is preferable.

@node @code{@@ref}
@section @code{@@ref}

@anchor{ref}@c old name
@findex ref
@cindex Cross-references using @code{@@ref}
@cindex References using @code{@@ref}

@code{@@ref} is nearly the same as @code{@@xref} except that it does
not generate a `See' in the printed output, just the reference itself.
This makes it useful as the last part of a sentence.

@noindent For example,

@cindex Hurricanes
@example
For more information, @@pxref@{This@}, and @@ref@{That@}.
@end example

@noindent
produces in Info:

@example
For more information, *note This::, and *note That::.
@end example

@noindent
and in printed output:

@quotation
For more information, see Section 1.1 [This], page 1,
and Section 1.2 [That], page 2.
@end quotation

The @code{@@ref} command can tempt writers to express themselves in a
manner that is suitable for a printed manual but looks awkward in the
Info format.  Bear in mind that your audience could be using both the
printed and the Info format.  For example:

@cindex Sea surges
@example
Sea surges are described in @@ref@{Hurricanes@}.
@end example

@noindent
looks ok in the printed output:

@quotation
Sea surges are described in Section 6.7 [Hurricanes], page 72.
@end quotation

@noindent
but is awkward to read in Info, ``note'' being a verb:

@example
Sea surges are described in *note Hurricanes::.
@end example

@node @code{@@pxref}
@section @code{@@pxref}

@anchor{pxref}@c old name
@findex pxref
@cindex Cross-references using @code{@@pxref}
@cindex References using @code{@@pxref}

The parenthetical reference command, @code{@@pxref}, is nearly the
same as @code{@@xref}, but it is best used at the end of a sentence or
before a closing parenthesis.  The command differs from @code{@@xref}
in that @TeX{} typesets the reference for the printed manual with a
lowercase `see' rather than an uppercase `See'.

@noindent
With one argument, a parenthetical cross-reference looks like this:

@cindex Flooding
@example
@dots{} storms cause flooding (@@pxref@{Hurricanes@}) @dots{}
@end example

@need 800
@noindent
which produces

@example
@group
@dots{} storms cause flooding (*note Hurricanes::) @dots{}
@end group
@end example

@noindent
in Info and

@quotation
@dots{} storms cause flooding (see Section 6.7 [Hurricanes], page 72) @dots{}
@end quotation

@noindent
in a printed manual.

With two arguments, a parenthetical cross-reference has this template:

@example
@dots{} (@@pxref@{@var{node-name}, @var{cross-reference-name}@}) @dots{}
@end example

@noindent
which produces

@example
@dots{} (*note @var{cross-reference-name}: @var{node-name}.) @dots{}
@end example

@noindent
in Info and

@quotation
@dots{} (see Section @var{nnn} [@var{node-name}], page @var{ppp}) @dots{}
@end quotation

@noindent
in a printed manual.

@code{@@pxref} can be used with up to five arguments, just like
@code{@@xref} (@pxref{@code{@@xref}}).

In past versions of Texinfo, it was not allowed to write punctuation
after a @code{@@pxref}, so it could be used @emph{only} before a
right parenthesis.  This is no longer the case, so now it can be used
(for example) at the end of a sentence, where a lowercase ``see''
works best.  For instance:

@example
@dots{} For more information, @@pxref@{More@}.
@end example

@noindent
which outputs (in Info):

@example
@dots{} For more information, *note More::.
@end example

As a matter of style, @code{@@pxref} is best used at the ends of
sentences.  Although it technically works in the middle of a sentence,
that location breaks up the flow of reading.

@node @code{@@anchor}
@section @code{@@anchor}: Defining Arbitrary Cross-reference Targets

@anchor{anchor}@c old name
@findex anchor
@cindex Anchors
@cindex Cross-reference targets, arbitrary
@cindex Targets for cross-references, arbitrary

An @dfn{anchor} is a position in your document, labelled so that
cross-references can refer to it, just as they can to nodes.  You
create an anchor with the @code{@@anchor} command, and give the label
as a normal brace-delimited argument.  For example:

@example
This marks the @@anchor@{x-spot@}spot.
@dots{}
@@xref@{x-spot,,the spot@}.
@end example

@noindent produces:

@example
This marks the spot.
@dots{}
See [the spot], page 1.
@end example

As you can see, the @code{@@anchor} command itself produces no output.
This example defines an anchor `x-spot' just before the word `spot'.
You can refer to it later with an @code{@@xref} or other cross
reference command, as shown (@pxref{Cross References}).

It is best to put @code{@@anchor} commands just before the position you
wish to refer to; that way, the reader's eye is led on to the correct
text when they jump to the anchor.  You can put the @code{@@anchor}
command on a line by itself if that helps readability of the source.
Whitespace (including newlines) is ignored after @code{@@anchor}.

Anchor names and node names may not conflict.  Anchors and nodes are
given similar treatment in some ways; for example, the
@code{goto-node} command takes either an anchor name or a node name as
an argument.  (@xref{Go to node,,, info, Info}.)

Also like node names, anchor names cannot include some characters
(@pxref{Node Line Requirements}).

@cindex Nodes, deleting or renaming
Because of this duality, when you delete or rename a node, it is
usually a good idea to define an @code{@@anchor} with the old name.
That way, any links to the old node, whether from other Texinfo
manuals or general web pages, keep working.  You can also do this with
the @file{RENAMED_NODES_FILE} feature of @command{makeinfo}
(@pxref{HTML Xref Link Preservation}).  Both methods keep links
on the web working; the only substantive difference is that defining
anchors also makes the old node names available when reading the
document in Info.

@node @code{@@inforef}
@section @code{@@inforef}: Cross-references to Info-only Material

@anchor{inforef}@c old name
@findex inforef
@cindex Cross-references using @code{@@inforef}
@cindex References using @code{@@inforef}

@code{@@inforef} is used for making cross-references to Info
documents---even from a printed manual.  This might be because you
want to refer to conditional @code{@@ifinfo} text
(@pxref{Conditionals}), or because printed output is not available
(perhaps because there is no Texinfo source), among other
possibilities.

The command takes either two or three arguments, in the following
order:

@enumerate
@item
The node name.

@item
The cross-reference name (optional).

@item
The Info file name.
@end enumerate

@noindent
The template is:

@example
@@inforef@{@var{node-name}, @var{cross-reference-name}, @var{info-file-name}@}
@end example

@need 800
@noindent
For example,

@example
@group
@@inforef@{Advanced, Advanced Info commands, info@},
for more information.
@end group
@end example

@need 800
@noindent
produces (in Info):

@example
@group
*Note Advanced Info commands: (info)Advanced,
for more information.
@end group
@end example

@need 800
@noindent
and (in the printed output):

@quotation
See Info file @file{info}, node @samp{Advanced}, for more information.
@end quotation

(This particular example is not realistic, since the Info manual is
written in Texinfo, so all formats are available.  In fact, we don't
know of any extant Info-only manuals.)

The converse of @code{@@inforef} is @code{@@cite}, which is used to
refer to printed works for which no Info form exists.
@xref{@code{@@cite}}.

@node @code{@@url}
@section @code{@@url}, @code{@@uref@{@var{url}[, @var{text}][, @var{replacement}]@}}

@anchor{uref}@c old name
@findex uref
@cindex Uniform resource locator, referring to
@cindex URL, referring to

@cindex @code{href}, producing HTML
@code{@@uref} produces a reference to a uniform resource locator
(url).  It takes one mandatory argument, the url, and two optional
arguments which control the text that is displayed.  In HTML and PDF
output, @code{@@uref} produces a link you can follow.  (To merely
indicate a url without creating a link people can follow, use
@code{@@indicateurl}, @pxref{@code{@@indicateurl}}.)

@findex url
@anchor{url}@code{@@url} is a synonym for @code{@@uref}.
(Originally, @code{@@url} had the meaning of @code{@@indicateurl}, but
in practice it was almost always misused.  So we've changed the
meaning.)

The second argument, if specified, is the text to display (the default
is the url itself); in Info, DVI, and PDF output, but not in HTML
output, the url is output in addition to this text.

@cindex Man page, reference to
The third argument, if specified, is the text to display, but in this
case the url is not output in any format.  This is useful when the
text is already sufficiently referential, as in a man page.  Also, if
the third argument is given, the second argument is ignored.

@menu
* @code{@@url} Examples::           Examples of using all the forms of @code{@@url}.
* URL Line Breaking::       How lines are broken within @code{@@url} text.
* @code{@@url} PDF Output Format::  A special option to hide links in PDF output.
* PDF Colors::              Colorizing urls and other links in PDF output.
@end menu

@node @code{@@url} Examples
@subsection @code{@@url} Examples

@cindex @code{@@url}, examples of using
@cindex URL, examples of displaying

First, here is an example of the simplest form of @code{@@url}, with
just one argument.  The given url is both the target and the visible
text of the link:

@example
The official GNU ftp site is @@uref@{http://ftp.gnu.org/gnu@}.
@end example

@noindent produces:
@display
The official GNU ftp site is @uref{http://ftp.gnu.org/gnu}.
@end display

@subsubheading Two-argument form of @code{@@url}

Here is an example of the two-argument form:
@example
The official @@uref@{http://ftp.gnu.org/gnu, GNU ftp site@}
holds programs and texts.
@end example

@noindent which produces:
@display
The official @uref{http://ftp.gnu.org/gnu, GNU ftp site}
holds programs and texts.
@end display

@noindent that is, the Info (and @TeX{}, etc.)@: output is this:
@example
The official GNU ftp site (http://ftp.gnu.org/gnu)
holds programs and texts.
@end example

@noindent while the HTML output is this:
@example
The official <a href="http://ftp.gnu.org/gnu">GNU ftp site</a>
holds programs and texts.
@end example

@subsubheading Three-argument form of @code{@@url}

Finally, an example of the three-argument form:
@example
The @@uref@{/man.cgi/1/ls,,ls@} program @dots{}
@end example

@noindent which, except for HTML, produces:
@display
The @uref{/man.cgi/1/ls,,ls} program @dots{}
@end display

@noindent but with HTML:
@example
The <a href="/man.cgi/1/ls">ls</a> program @dots{}
@end example

By the way, some people prefer to display urls in the unambiguous
format:

@display
<URL:http://@var{host}/@var{path}>
@end display

@noindent
@cindex @code{<URL...>} convention, not used
You can use this form in the input file if you wish.  We feel it's not
necessary to include the @samp{<URL:} and @samp{>} in the output,
since to be useful any software that tries to detect urls in text
already has to detect them without the @samp{<URL:}.

@node URL Line Breaking
@subsection URL Line Breaking

@cindex Line breaking, and urls
@cindex Breakpoints within urls
@TeX{} allows line breaking within urls at only a few characters
(which are special in urls): @samp{&}, @samp{.}, @samp{#}, @samp{?},
and @samp{/} (but not between two @samp{/} characters).  A tiny amount
of stretchable space is also inserted around these characters to help
with line breaking.

For HTML output, modern browsers will also do line breaking within
displayed urls.  If you need to allow breaks at other characters you
can insert @code{@@/} as needed (@pxref{Line Breaks}).

@findex urefbreakstyle
By default, in @TeX{} any such breaks at special characters will occur
after the character.  Some people prefer such breaks to happen before
the special character.  This can be controlled with the
@code{@@urefbreakstyle} command (this command has effect only in
@TeX{}):

@example
@@urefbreakstyle @var{how}
@end example

@noindent where the argument @var{how} is one of these words:

@vindex after@r{, value for @code{@@urefbreakstyle}}
@vindex before@r{, value for @code{@@urefbreakstyle}}
@vindex none@r{, value for @code{@@urefbreakstyle}}
@table @samp
@item after
(the default) Potentially break after the special characters.
@item before
Potentially break before the special characters.
@item none
Do not consider breaking at the special characters at all; any potential
breaks must be manually inserted.
@end table

@node @code{@@url} PDF Output Format
@subsection @code{@@url} PDF Output Format

@cindex PDF output of urls
@cindex URLs, PDF output of

If the ultimate purpose of a PDF is only to be viewed online, perhaps
similar to HTML in some inchoate way, you may not want the urls to be
included in the visible text (just as urls are not visible to readers
of web pages).  Texinfo provides a PDF-specific option for this, which
must be used inside @code{@@tex}:

@findex \urefurlonlylinktrue
@example
@@tex
\global\urefurlonlylinktrue
@@end tex
@end example

The result is that @code{@@url@{http://www.gnu.org, GNU@}} has the
visible output of just `GNU', with a link target of
@url{http://www.gnu.org}.  Ordinarily, the visible output would
include both the label and the url: `GNU (@url{http://www.gnu.org})'.

This option only has effect when the PDF output is produced with the
pdf@TeX{} program, not with other ways of getting from Texinfo to PDF
(e.g., @TeX{} to DVI to PDF)@.  Consequently, it is ok to specify this
option unconditionally within @code{@@tex}, as shown above.  It is
ignored when DVI is being produced.

@node PDF Colors
@subsection PDF Colors

@cindex Colored links, in PDF output
@cindex Links, coloring in PDF output
@cindex URLs, coloring in PDF output

By default, urls and cross-reference links are printed in black in PDF
output.  Very occasionally, however, you may want to highlight such
``live'' links with a different color, as is commonly done on web
pages.  Texinfo provides a PDF-specific option for specifying these
colors, which must be used inside @code{@@tex}:

@findex \linkcolor
@findex \urlcolor
@example
@@tex
\global\def\linkcolor@{1 0 0@}  % red
\global\def\urlcolor@{0 1 0@}   % green
@@end tex
@end example

@code{\urlcolor} changes the color of @code{@@url} output (both the
actual url and any textual label), while @code{\linkcolor} changes the
color for cross-references to nodes, etc.  They are independent.

@cindex RGB color specification.
The three given values must be numbers between 0 and 1, specifying the
amount of red, green, and blue respectively.

These definitions only have an effect when the PDF output is produced
with the pdf@TeX{} program, not with other ways of getting from
Texinfo to PDF (e.g., @TeX{} to DVI to PDF)@.  Consequently, it is ok
to specify this option unconditionally within @code{@@tex}, as shown
above.  It is ignored when DVI is being produced.

We do not recommend colorizing just for fun; unless you have a
specific reason to use colors, best to skip it.

@node @code{@@cite}
@section @code{@@cite}@{@var{reference}@}

@anchor{cite}@c old name
@findex cite

Use the @code{@@cite} command for the name of a book that lacks a
companion Info file.  The command produces italics in the printed
manual, and quotation marks in the Info file.

If a book is written in Texinfo, it is better to use a cross-reference
command since a reader can easily follow such a reference in Info.
@xref{@code{@@xref}}.

@node Marking Text
@chapter Marking Text, Words and Phrases
@cindex Paragraph, marking text within
@cindex Marking words and phrases
@cindex Words and phrases, marking them
@cindex Marking text within a paragraph
@cindex Text, marking up

In Texinfo, you can mark words and phrases in a variety of ways.
The Texinfo formatters use this information to determine how to
highlight the text.
You can specify, for example, whether a word or phrase is a
defining occurrence, a metasyntactic variable, or a symbol used in a
program.  Also, you can emphasize text, in several different ways.

@menu
* Indicating::                  How to indicate definitions, files, etc.
* Emphasis::                    How to emphasize text.
@end menu

@node Indicating
@section Indicating Definitions, Commands, etc.

@cindex Highlighting text
@cindex Indicating commands, definitions, etc.

Texinfo has commands for indicating just what kind of object a piece
of text refers to.  For example, email addresses are marked by
@code{@@email}; that way, the result can be a live link to send email
when the output format supports it.  If the email address was simply
marked as ``print in a typewriter font'', that would not be possible.

@menu
* Useful Highlighting::         Highlighting provides useful information.
* @code{@@code}::                       Indicating program code.
* @code{@@kbd}::                        Showing keyboard input.
* @code{@@key}::                        Specifying keys.
* @code{@@samp}::                       Indicating a literal sequence of characters.
* @code{@@verb}::                       Indicating a verbatim sequence of characters.
* @code{@@var}::                        Indicating metasyntactic variables.
* @code{@@env}::                        Indicating environment variables.
* @code{@@file}::                       Indicating file names.
* @code{@@command}::                    Indicating command names.
* @code{@@option}::                     Indicating option names.
* @code{@@dfn}::                        Specifying definitions.
* @code{@@abbr}::                       Indicating abbreviations.
* @code{@@acronym}::                    Indicating acronyms.
* @code{@@indicateurl}::                Indicating an example url.
* @code{@@email}::                      Indicating an electronic mail address.
@end menu

@node Useful Highlighting
@subsection Highlighting Commands are Useful

The commands serve a variety of purposes:

@table @code
@item @@code@{@var{sample-code}@}
Indicate text that is a literal example of a piece of a program.
@xref{@code{@@code}}.

@item @@kbd@{@var{keyboard-characters}@}
Indicate keyboard input.  @xref{@code{@@kbd}}.

@item @@key@{@var{key-name}@}
Indicate the conventional name for a key on a keyboard.
@xref{@code{@@key}}.

@item @@samp@{@var{text}@}
Indicate text that is a literal example of a sequence of characters.
@xref{@code{@@samp}}.

@item @@verb@{@var{text}@}
Write a verbatim sequence of characters.
@xref{@code{@@verb}}.

@item @@var@{@var{metasyntactic-variable}@}
Indicate a metasyntactic variable.  @xref{@code{@@var}}.

@item @@env@{@var{environment-variable}@}
Indicate an environment variable.  @xref{@code{@@env}}.

@item @@file@{@var{file-name}@}
Indicate the name of a file.  @xref{@code{@@file}}.

@item @@command@{@var{command-name}@}
Indicate the name of a command.
@xref{@code{@@command}}.

@item @@option@{@var{option}@}
Indicate a command-line option.
@xref{@code{@@option}}.

@item @@dfn@{@var{term}@}
Indicate the introductory or defining use of a term.
@xref{@code{@@dfn}}.

@item @@cite@{@var{reference}@}
Indicate the name of a book.  @xref{@code{@@cite}}.

@item @@abbr@{@var{abbreviation}@}
Indicate an abbreviation, such as `Comput.'.

@item @@acronym@{@var{acronym}@}
Indicate an acronym.  @xref{@code{@@acronym}}.

@item @@indicateurl@{@var{uniform-resource-locator}@}
Indicate an example (that is, nonfunctional) uniform resource locator.
@xref{@code{@@indicateurl}}.  (Use @code{@@url} (@pxref{@code{@@url}}) for
live urls.)

@item @@email@{@var{email-address}[, @var{displayed-text}]@}
Indicate an electronic mail address.  @xref{@code{@@email}}.

@end table

@node @code{@@code}
@subsection @code{@@code}@{@var{sample-code}@}

@anchor{code}@c old name
@findex code

@cindex Syntactic tokens, indicating
Use the @code{@@code} command to indicate text that is a piece of a
program and which consists of entire syntactic tokens.  Enclose the
text in braces.

@cindex Expressions in a program, indicating
@cindex Keywords, indicating
@cindex Reserved words, indicating
Thus, you should use @code{@@code} for an expression in a program, for
the name of a variable or function used in a program, or for a
keyword in a programming language.

Use @code{@@code} for command names in languages that resemble
programming languages, such as Texinfo.  For example, @code{@@code} and
@code{@@samp} are produced by writing @samp{@@code@{@@@@code@}} and
@samp{@@code@{@@@@samp@}} in the Texinfo source, respectively.

@cindex Case, not altering in @code{@@code}
It is incorrect to alter the case of a word inside a @code{@@code}
command when it appears at the beginning of a sentence.  Most computer
languages are case sensitive.  In C, for example, @code{Printf} is
different from the identifier @code{printf}, and most likely is a
misspelling of it.  Even in languages which are not case sensitive, it
is confusing to a human reader to see identifiers spelled in different
ways.  Pick one spelling and always use that.  If you do not want to
start a sentence with a command name written all in lowercase, you
should rearrange the sentence.

In the Info output, @code{@@code} results in single quotation marks
around the text.  In other formats, @code{@@code} argument is typeset
in a typewriter (monospace) font.  For example,

@example
The function returns @@code@{nil@}.
@end example

@noindent
produces this:

@quotation
The function returns @code{nil}.
@end quotation

Here are some cases for which it is preferable @emph{not} to use @code{@@code}:

@itemize @bullet
@item
For shell command names such as @command{ls} (use @code{@@command}).

@item
For environment variable such as @env{TEXINPUTS} (use @code{@@env}).

@item
For shell options such as @samp{-c} when such options stand alone (use
@code{@@option}).

@item
An entire shell command often looks better if written using
@code{@@samp} rather than @code{@@code}.  In this case, the rule is to
choose the more pleasing format.

@item
For a string of characters shorter than a syntactic token.  For example,
if you are writing about @samp{goto-ch}, which is just a part of the
name for the @code{goto-char} Emacs Lisp function, you should use
@code{@@samp}.

@item
In general, when writing about the characters used in a token; for
example, do not use @code{@@code} when you are explaining what letters
or printable symbols can be used in the names of functions.  (Use
@code{@@samp}.)  Also, you should not use @code{@@code} to mark text
that is considered input to programs unless the input is written in a
language that is like a programming language.  For example, you should
not use @code{@@code} for the keystroke commands of GNU Emacs (use
@code{@@kbd} instead) although you may use @code{@@code} for the names
of the Emacs Lisp functions that the keystroke commands invoke.

@end itemize

By default, @TeX{} will consider breaking lines at @samp{-} and
@samp{_} characters within @code{@@code} and related commands.  This
can be controlled with @code{@@allowcodebreaks}
(@pxref{@code{@@allowcodebreaks}}).  The HTML output attempts to
respect this for @samp{-}, but ultimately it is up to the browser's
behavior.  For Info, it seems better never to make such breaks.

For Info, the quotes are omitted in the output of the @code{@@code}
command and related commands (e.g., @code{@@kbd}, @code{@@command}),
in typewriter-like contexts such as the @code{@@example} environment
(@pxref{@code{@@example}}) and @code{@@code} itself, etc.

To control which quoting characters are implicitly inserted by Texinfo
processors in the output of @samp{@@code}, etc., see the
@code{OPEN_QUOTE_SYMBOL} and @code{CLOSE_QUOTE_SYMBOL} customization
variables (@pxref{Other Customization Variables}).  This is separate
from how actual quotation characters in the input document are handled
(@pxref{Inserting Quote Characters}).

@node @code{@@kbd}
@subsection @code{@@kbd}@{@var{keyboard-characters}@}

@anchor{kbd}@c old name
@findex kbd
@cindex Keyboard input

Use the @code{@@kbd} command for characters of input to be typed by
users.  For example, to refer to the characters @kbd{M-a}, write:

@example
@@kbd@{M-a@}
@end example

@noindent
and to refer to the characters @kbd{M-x shell}, write:

@example
@@kbd@{M-x shell@}
@end example

@cindex User input
@cindex Slanted typewriter font, for @code{@@kbd}
By default, the @code{@@kbd} command produces a different font
(slanted typewriter instead of normal typewriter),
so users can distinguish the characters that they are supposed
to type from those that the computer outputs.

@findex kbdinputstyle
Since the usage of @code{@@kbd} varies from manual to manual, you can
control the font switching with the @code{@@kbdinputstyle} command.
This command has no effect on Info output.  Write this command at the
beginning of a line with a single word as an argument, one of the
following:

@vindex distinct@r{, value for @code{@@kbdinputstyle}}
@vindex example@r{, value for @code{@@kbdinputstyle}}
@vindex code@r{, value for @code{@@kbdinputstyle}}
@table @samp
@item code
Always use the same font for @code{@@kbd} as @code{@@code}.
@item example
Use the distinguishing font for @code{@@kbd} only in @code{@@example}
and similar environments.
@item distinct
(the default) Always use the distinguishing font for @code{@@kbd}.
@end table

You can embed another @@-command inside the braces of a @code{@@kbd}
command.  Here, for example, is the way to describe a command that
would be described more verbosely as ``press the @samp{r} key and then
press the @key{RETURN} key'':

@example
@@kbd@{r @@key@{RET@}@}
@end example

@noindent
This produces: @kbd{r @key{RET}}.  (The present manual uses the
default for @code{@@kbdinputstyle}.)

You also use the @code{@@kbd} command if you are spelling out the letters
you type; for example:

@example
To give the @@code@{logout@} command,
type the characters @@kbd@{l o g o u t @@key@{RET@}@}.
@end example

@noindent
This produces:

@quotation
To give the @code{logout} command,
type the characters @kbd{l o g o u t @key{RET}}.
@end quotation

(Also, this example shows that you can add spaces for clarity.  If you
explicitly want to mention a space character as one of the characters of
input, write @kbd{@@key@{SPC@}} for it.)

@node @code{@@key}
@subsection @code{@@key}@{@var{key-name}@}

@anchor{key}@c old name
@findex key

Use the @code{@@key} command for the conventional name for a key on a
keyboard, as in:

@example
@@key@{RET@}
@end example

You can use the @code{@@key} command within the argument of an
@code{@@kbd} command when the sequence of characters to be typed
includes one or more keys that are described by name.

For example, to produce @kbd{C-x @key{ESC}} and @kbd{M-@key{TAB}} you
would type:

@example
@@kbd@{C-x @@key@{ESC@}@}
@@kbd@{M-@@key@{TAB@}@}
@end example

Here is a list of the recommended names for keys:
@cindex Recommended names for keys
@cindex Keys, recommended names
@cindex Names recommended for keys
@cindex Abbreviations for keys
@cindex Control keys, specifying
@cindex Meta keys, specifying

@quotation
@table @t
@item SPC
Space
@item RET
Return
@item LFD
Linefeed (however, since most keyboards nowadays do not have a Linefeed key,
it might be better to call this character @kbd{C-j})
@item TAB
Tab
@item BS
Backspace
@item ESC
Escape
@item DELETE
Delete
@item SHIFT
Shift
@item CTRL
Control
@item META
Meta
@end table
@end quotation

@cindex META key
There are subtleties to handling words like `meta' or `ctrl' that are
names of modifier keys.  When mentioning a character in which the
modifier key is used, such as @kbd{Meta-a}, use the @code{@@kbd} command
alone; do not use the @code{@@key} command; but when you are referring
to the modifier key in isolation, use the @code{@@key} command.  For
example, write @samp{@@kbd@{Meta-a@}} to produce @kbd{Meta-a} and
@samp{@@key@{META@}} to produce @key{META}.

@c per rms.
As a convention in GNU manuals, @code{@@key} should not be used in
index entries.

@node @code{@@samp}
@subsection @code{@@samp}@{@var{text}@}

@anchor{samp}@c old name
@findex samp

Use the @code{@@samp} command to indicate text that is a literal example
or `sample' of a sequence of characters in a file, string, pattern, etc.
Enclose the text in braces.  The argument appears within single
quotation marks in both the Info file and the printed manual; in
addition, it is printed in a fixed-width font.

@example
To match @@samp@{foo@} at the end of the line,
use the regexp @@samp@{foo$@}.
@end example

@noindent
produces

@quotation
To match @samp{foo} at the end of the line, use the regexp
@samp{foo$}.
@end quotation

Any time you are referring to single characters, you should use
@code{@@samp} unless @code{@@kbd} or @code{@@key} is more appropriate.
Also, you may use @code{@@samp} for entire statements in C and for entire
shell commands---in this case, @code{@@samp} often looks better than
@code{@@code}.  Basically, @code{@@samp} is a catchall for whatever is
not covered by @code{@@code}, @code{@@kbd}, @code{@@key},
@code{@@command}, etc.

Only include punctuation marks within braces if they are part of the
string you are specifying.  Write punctuation marks outside the braces
if those punctuation marks are part of the English text that surrounds
the string.  In the following sentence, for example, the commas and
period are outside of the braces:

@example
@group
In English, the vowels are @@samp@{a@}, @@samp@{e@},
@@samp@{i@}, @@samp@{o@}, @@samp@{u@}, and sometimes
@@samp@{y@}.
@end group
@end example

@noindent
This produces:

@quotation
In English, the vowels are @samp{a}, @samp{e},
@samp{i}, @samp{o}, @samp{u},  and sometimes
@samp{y}.
@end quotation

@node @code{@@verb}
@subsection @code{@@verb}@{@var{char}@var{text}@var{char}@}

@anchor{verb}@c old name
@findex verb
@cindex Verbatim in-line text

@cindex Delimiter character, for verbatim
Use the @code{@@verb} command to print a verbatim sequence of
characters.

Like @LaTeX{}'s @code{\verb} command, the verbatim text can be quoted using
any unique delimiter character.  Enclose the verbatim text, including the
delimiters, in braces.  Text is printed in a fixed-width font:

@example
How many @@verb@{|@@|@}-escapes does one need to print this
@@verb@{.@@a @@b.@@c.@} string or @@verb@{+@@'e?`@{@}!`\+@} this?
@end example

@noindent
produces

@example
How many @verb{|@|}-escapes does one need to print this
@verb{.@a @b.@c.} string or @verb{+@'e?`{}!`\+} this?
@end example

This is in contrast to @code{@@samp} (see the previous section),
@code{@@code}, and similar commands; in those cases, the argument is
normal Texinfo text, where the three characters @code{@@@{@}} are
special, as usual.  With @code{@@verb}, nothing is special except the
delimiter character you choose.

The delimiter character itself may appear inside the verbatim text, as
shown above.  As another example, @samp{@@verb@{...@}} prints a single
(fixed-width) period.

It is not reliable to use @code{@@verb} inside other Texinfo
constructs.  In particular, it does not work to use @code{@@verb} in
anything related to cross-referencing, such as section titles or
figure captions.

@node @code{@@var}
@subsection @code{@@var}@{@var{metasyntactic-variable}@}

@anchor{var}@c old name
@findex var

Use the @code{@@var} command to indicate metasyntactic variables.  A
@dfn{metasyntactic variable} is something that stands for another
piece of text.  For example, you should use a metasyntactic variable
in the documentation of a function to describe the arguments that are
passed to that function.

Do not use @code{@@var} for the names of normal variables in computer
programs.  These are specific names, so @code{@@code} is correct for
them (@code{@@code}).  For example, the Emacs Lisp variable
@code{texinfo-tex-command} is not a metasyntactic variable; it is
properly formatted using @code{@@code}.

Do not use @code{@@var} for environment variables either; @code{@@env}
is correct for them (see the next section).

The effect of @code{@@var} in the Info file is to change the case of
the argument to all uppercase.  In the printed manual and HTML
output, the argument is output in slanted type.

@need 700
For example,

@example
To delete file @@var@{filename@},
type @@samp@{rm @@var@{filename@}@}.
@end example

@noindent
produces

@quotation
To delete file @var{filename}, type @samp{rm @var{filename}}.
@end quotation

@noindent
(Note that @code{@@var} may appear inside @code{@@code},
@code{@@samp}, @code{@@file}, etc.)

Write a metasyntactic variable all in lowercase without spaces, and
use hyphens to make it more readable.  Thus, the Texinfo source for
the illustration of how to begin a Texinfo manual looks like
this:

@example
@group
\input texinfo
@@@@settitle @@var@{name-of-manual@}
@end group
@end example

@noindent
This produces:

@example
@group
\input texinfo
@@settitle @var{name-of-manual}
@end group
@end example

In some documentation styles, metasyntactic variables are shown with
angle brackets, for example:

@example
@dots{}, type rm <filename>
@end example

@noindent
However, that is not the style that Texinfo uses.

@c FIXME add a customization variable?  Add an example on how to do that
@c for HTML?
@c (You can, of course, modify the sources to @file{texinfo.tex}
@c and the Info formatting commands
@c to output the @code{<@dots{}>} format if you wish.)

@node @code{@@env}
@subsection @code{@@env}@{@var{environment-variable}@}

@anchor{env}@c old name
@findex env

Use the @code{@@env} command to indicate environment variables, as
used by many operating systems, including GNU@.  Do not use it for
@emph{meta}syntactic variables; use @code{@@var} for those (see the
previous section).

@code{@@env} is equivalent to @code{@@code} in its effects.
For example:

@example
The @@env@{PATH@} environment variable @dots{}
@end example
@noindent produces
@quotation
The @env{PATH} environment variable @dots{}
@end quotation

@node @code{@@file}
@subsection @code{@@file}@{@var{file-name}@}

@anchor{file}@c old name
@findex file

Use the @code{@@file} command to indicate text that is the name of a
file, buffer, or directory, or is the name of a node in Info.  You can
also use the command for file name suffixes.  Do not use @code{@@file}
for symbols in a programming language; use @code{@@code}.

@code{@@file} is equivalent to @code{code} in its effects.  For
example,

@example
The @@file@{.el@} files are in
the @@file@{/usr/local/emacs/lisp@} directory.
@end example

@noindent
produces

@quotation
The @file{.el} files are in
the @file{/usr/local/emacs/lisp} directory.
@end quotation

@node @code{@@command}
@subsection @code{@@command}@{@var{command-name}@}

@anchor{command}@c old name
@findex command
@cindex Command names, indicating
@cindex Program names, indicating

Use the @code{@@command} command to indicate command names, such as
@command{ls} or @command{cc}.

@code{@@command} is equivalent to @code{@@code} in its effects.
For example:

@example
The command @@command@{ls@} lists directory contents.
@end example
@noindent produces
@quotation
The command @command{ls} lists directory contents.
@end quotation

You should write the name of a program in the ordinary text font, rather
than using @code{@@command}, if you regard it as a new English word,
such as `Emacs' or `Bison'.

When writing an entire shell command invocation, as in @samp{ls -l},
you should use either @code{@@samp} or @code{@@code} at your discretion.

@node @code{@@option}
@subsection @code{@@option}@{@var{option-name}@}

@anchor{option}@c old name
@findex option

Use the @code{@@option} command to indicate a command-line option; for
example, @option{-l} or @option{--version} or
@option{--output=@var{filename}}.

@code{@@option} is equivalent to @code{@@code} in its effects.
For example:

@example
The option @@option@{-l@} produces a long listing.
@end example
@noindent produces
@quotation
The option @option{-l} produces a long listing.
@end quotation

@node @code{@@dfn}
@subsection @code{@@dfn}@{@var{term}@}

@anchor{dfn}@c old name
@findex dfn

Use the @code{@@dfn} command to identify the introductory or defining
use of a technical term.  Use the command only in passages whose
purpose is to introduce a term which will be used again or which the
reader ought to know.  Mere passing mention of a term for the first
time does not deserve @code{@@dfn}.  The command generates italics in
the printed manual, and double quotation marks in the Info file.  For
example:

@example
Getting rid of a file is called @@dfn@{deleting@} it.
@end example

@noindent
produces

@quotation
Getting rid of a file is called @dfn{deleting} it.
@end quotation

As a general rule, a sentence containing the defining occurrence of a
term should be a definition of the term.  The sentence does not need
to say explicitly that it is a definition, but it should contain the
information of a definition---it should make the meaning clear.

@node @code{@@abbr}
@subsection @code{@@abbr}@{@var{abbreviation}[, @var{meaning}]@}

@anchor{abbr}@c old name
@findex abbr

@cindex Abbreviations, tagging
You can use the @code{@@abbr} command for general abbreviations.  The
abbreviation is given as the single argument in braces, as in
@samp{@@abbr@{Comput.@}}.  As a matter of style, or for particular
abbreviations, you may prefer to omit periods, as in
@samp{@@abbr@{Mr@} Stallman}.

@code{@@abbr} accepts an optional second argument, intended to be used
for the meaning of the abbreviation.

If the abbreviation ends with a lowercase letter and a period, and is
not at the end of a sentence, and has no second argument, remember to
use the @code{@@.} command (@pxref{Ending a Sentence}) to get the
correct spacing.  However, you do not have to use @code{@@.} within
the abbreviation itself; Texinfo automatically assumes periods within
the abbreviation do not end a sentence.

@cindex @code{<abbr>} and @code{<abbrev>} tags
In @TeX{} and in the Info output, the first argument is printed as-is;
if the second argument is present, it is printed in parentheses after
the abbreviation.  In HTML the @code{<abbr>} tag is used; in Docbook,
the @code{<abbrev>} tag is used.  For instance:

@example
@@abbr@{Comput. J., Computer Journal@}
@end example

@noindent produces:

@display
@abbr{Comput. J., Computer Journal}
@end display

For abbreviations consisting of all capital letters, you may prefer to
use the @code{@@acronym} command instead.  See the next section for
more on the usage of these two commands.

@node @code{@@acronym}
@subsection @code{@@acronym}@{@var{acronym}[, @var{meaning}]@}

@anchor{acronym}@c old name
@findex acronym

@cindex NASA, as acronym
@cindex Acronyms, tagging
You can use the @code{@@acronym} command for abbreviations written in
all capital letters, such as `@acronym{NASA}'.  The abbreviation is
given as the single argument in braces, as in
@samp{@@acronym@{NASA@}}.  As a matter of style, or for particular
acronyms, you may prefer to use periods, as in
@samp{@@acronym@{N.A.S.A.@}}.

@code{@@acronym} accepts an optional second argument, intended to be
used for the meaning of the acronym.

If the acronym is at the end of a sentence, and if there is no second
argument, remember to use the @code{@@.} or similar command
(@pxref{Ending a Sentence}) to get the correct spacing.

@cindex @code{<acronym>} tag
In @TeX{}, the acronym is printed in slightly smaller font.  In the
Info output, the argument is printed as-is.  In either format, if the
second argument is present, it is printed in parentheses after the
acronym.  In HTML and Docbook the @code{<acronym>} tag is used.

For instance (since GNU is a recursive acronym, we use
@code{@@acronym} recursively):

@example
@@acronym@{GNU, @@acronym@{GNU@}'s Not Unix@}
@end example

@noindent produces:

@display
@acronym{GNU, @acronym{GNU}'s Not Unix}
@end display

@cindex Family names, in all capitals
In some circumstances, it is conventional to print family names in all
capitals.  Don't use @code{@@acronym} for this, since a name is not an
acronym.  Use @code{@@sc} instead (@pxref{Smallcaps}).

@code{@@abbr} and @code{@@acronym} are closely related commands: they
both signal to the reader that a shortened form is being used, and
possibly give a meaning.  When choosing whether to use these two
commands, please bear the following in mind.

@itemize @minus
@item
In common English usage, acronyms are a subset of abbreviations: they
include pronounceable words like `@acronym{NATO}', `radar', and
`snafu'; some sources also include syllable acronyms like
`Usenet', hybrids like `@acronym{SIGGRAPH}', and unpronounceable
initialisms like `@acronym{FBI}'.

@item
In Texinfo, an acronym (but not an abbreviation) should consist only
of capital letters and periods, no lowercase.

@item
In @TeX{}, an acronym (but not an abbreviation) is printed in a
slightly smaller font.

@item
Some browsers place a dotted bottom border under abbreviations but not
acronyms.

@item
It usually turns out to be quite difficult and/or time-consuming to
consistently use @code{@@acronym} for all sequences of uppercase
letters.  Furthermore, it looks strange for some acronyms to be in the
normal font size and others to be smaller.  Thus, a simpler approach
you may wish to consider is to avoid @code{@@acronym} and just typeset
everything as normal text in all capitals: @samp{GNU}, producing the
output `GNU'.

@item
In general, it's not essential to use either of these commands for all
abbreviations; use your judgment.  Text is perfectly readable without
them.
@end itemize

@node @code{@@indicateurl}
@subsection @code{@@indicateurl}@{@var{uniform-resource-locator}@}

@anchor{indicateurl}@c old name
@findex indicateurl
@cindex Uniform resource locator, indicating
@cindex URL, indicating

Use the @code{@@indicateurl} command to indicate a uniform resource
locator on the World Wide Web.  This is purely for markup purposes and
does not produce a link you can follow (use the @code{@@url} or
@code{@@uref} command for that, @pxref{@code{@@url}}).
@code{@@indicateurl} is useful for urls which do not actually exist.
For example:

@example
For example, the url might be @@indicateurl@{http://example.org/path@}.
@end example

@noindent which produces:

@display
For example, the url might be @indicateurl{http://example.org/path}.
@end display

The output from @code{@@indicateurl} is more or less like that of
@code{@@samp} (@pxref{@code{@@samp}}).

@node @code{@@email}
@subsection @code{@@email}@{@var{email-address}[, @var{displayed-text}]@}

@anchor{email}@c old name
@findex email

Use the @code{@@email} command to indicate an electronic mail address.
It takes one mandatory argument, the address, and one optional argument, the
text to display (the default is the address itself).

@cindex Mailto link
In Info, the address is shown in angle brackets, preceded by the text
to display if any.  In @TeX{}, the angle brackets are omitted.  In
HTML output, @code{@@email} produces a @samp{mailto} link that usually
brings up a mail composition window.  For example:

@example
Send bug reports to @@email@{bug-texinfo@@@@gnu.org@},
suggestions to the @@email@{bug-texinfo@@@@gnu.org, same place@}.
@end example

@noindent produces

@display
Send bug reports to @email{bug-texinfo@@gnu.org},
suggestions to the @email{bug-texinfo@@gnu.org, same place}.
@end display

@node Emphasis
@section Emphasizing Text
@cindex Emphasizing text

Usually, Texinfo changes the font to mark words in the text according
to the category the words belong to; an example is the @code{@@code}
command.  Most often, this is the best way to mark words.  However,
sometimes you will want to emphasize text without indicating a
category.  Texinfo has two commands to do this.  Also, Texinfo has
several commands that specify the font in which text will be output.
These commands have no effect in Info and only one of them, the
@code{@@r} command, has any regular use.

@menu
* @code{@@emph @@strong}::               How to emphasize text in Texinfo.
* Smallcaps::                   How to use the small caps font.
* Fonts::                       Various font commands for printed output.
@end menu

@node @code{@@emph @@strong}
@subsection @code{@@emph}@{@var{text}@} and @code{@@strong}@{@var{text}@}

@anchor{emph & strong}@c oldname
@findex emph
@findex strong
@cindex Emphasizing text, font for

The @code{@@emph} and @code{@@strong} commands are for emphasis;
@code{@@strong} is stronger.  In printed output, @code{@@emph} produces
@emph{italics} and @code{@@strong} produces @strong{bold}.
In the Info output, @code{@@emph} surrounds the text with underscores
(@samp{_}), and @code{@@strong} puts asterisks around the text.

For example,

@example
@group
@@strong@{Caution:@} @@samp@{rm *@}
removes @@emph@{all@} normal files.
@end group
@end example

@noindent
produces the following:

@quotation
@strong{Caution}: @samp{rm * .[^.]*}
removes @emph{all} normal files.
@end quotation

The @code{@@strong} command is seldom used except to mark what is, in
effect, a typographical element, such as the word `Caution' in the
preceding example.

@quotation Caution
Do not use @code{@@strong} with the word @samp{Note} followed by a
space; Info will mistake the combination for a cross-reference.  Use a
phrase such as @strong{Please notice} or @strong{Caution} instead, or
the optional argument to @code{@@quotation}---@samp{Note} is allowable
there.
@end quotation

@node Smallcaps
@subsection @code{@@sc}@{@var{text}@}: The Small Caps Font
@cindex Small caps font
@findex sc @r{(small caps font)}

Use the @samp{@@sc} command to set text in @sc{a small caps font}
(where possible).  Write the text you want to be in small caps between
braces in lowercase, like this:

@example
Richard @@sc@{Stallman@} commenc@'{e} GNU.
@end example

@noindent
This produces:

@display
Richard @sc{Stallman} commenc@'{e} GNU.
@end display

As shown here, we recommend reserving @code{@@sc} for special cases
where you want typographic small caps; family names are one such,
especially in languages other than English, though there are no
hard-and-fast rules about such things.

@cindex @code{<small>} tag
@TeX{} typesets any uppercase letters between the braces of an
@code{@@sc} command in full-size capitals; only lowercase letters are
printed in the small caps font.  In the Info output, the argument to
@code{@@sc} is printed in all uppercase.  In HTML, the argument is
uppercased and the output marked with the @code{<small>} tag to reduce
the font size, since HTML cannot easily represent true small caps.

Overall, we recommend using standard upper- and lowercase letters
wherever possible.

@node Fonts
@subsection Fonts for Printing
@cindex Fonts for printing

@findex fonttextsize
@cindex Font size, reducing
@cindex Reducing font size
@cindex Smaller fonts
Texinfo provides one command to change the size of the main body font
in the @TeX{} output for a document: @code{@@fonttextsize}.  It has no
effect in other output.  It takes a single argument on the remainder
of the line, which must be either @samp{10} or @samp{11}.  For
example:

@example
@@fonttextsize 10
@end example

@cindex Printing cost, reducing
The effect is to reduce the body font to a 10@dmn{pt} size (the
default is 11@dmn{pt}).  Fonts for other elements, such as sections
and chapters, are reduced accordingly.  This should only be used in
conjunction with @code{@@smallbook} (@pxref{@code{@@smallbook}}) or
similar, since 10@dmn{pt} fonts on standard paper (8.5x11 or A4) are
too small.  One reason to use this command is to save pages, and hence
printing cost, for physical books.

Texinfo does not at present have commands to switch the font family
to use, or more general size-changing commands.

Texinfo also provides a number of font commands that specify font
changes in the printed manual and (where possible) in the HTML output.
They have no effect in Info.  All the commands apply to a following
argument surrounded by braces.

@table @code
@item @@b
@findex b @r{(bold font)}
@cindex Bold font
selects @b{bold} face;

@item @@i
@findex i @r{(italic font)}
@cindex Italic font
selects an @i{italic} font;

@item @@r
@findex r @r{(roman font)}
@cindex Roman font
@cindex Default font
selects a @r{roman} font, which is the usual font in which text is
printed.  It may or may not be seriffed.

@item @@sansserif
@findex sansserif @r{(sans serif font)}
@cindex Sans serif font
selects a @sansserif{sans serif} font;

@item @@slanted
@findex slanted @r{(slanted font)}
@cindex Slanted font
@cindex Oblique font
selects a @slanted{slanted} font;

@item @@t
@findex t @r{(typewriter font)}
@cindex Monospace font
@cindex Fixed-width font
@cindex Typewriter font
selects the @t{fixed-width}, typewriter-style font used by @code{@@code};

@end table

(The commands with longer names were invented much later than the
others, at which time it did not seem desirable to use very short
names for such infrequently needed features.)

@cindex @code{<lineannotation>} Docbook tag
The @code{@@r} command can be useful in example-like environments, to
write comments in the standard roman font instead of the fixed-width
font.  This looks better in printed output, and produces a
@code{<lineannotation>} tag in Docbook output.

For example,

@example
@group
@@lisp
(+ 2 2)    ; @@r@{Add two plus two.@}
@@end lisp
@end group
@end example

@noindent
produces

@lisp
(+ 2 2)    ; @r{Add two plus two.}
@end lisp

The @code{@@t} command can occasionally be useful to produce output in
a typewriter font where that is supported (e.g., HTML and PDF), but no
distinction is needed in Info or plain text: @code{@@t@{foo@}}
produces @t{foo}, cf. @code{@@code@{foo@}} producing @code{foo}.

In general, the other font commands are unlikely to be useful; they
exist primarily to make it possible to document the functionality of
specific font effects, such as in @TeX{} and related packages.

@node Quotations and Examples
@chapter Quotations and Examples

Quotations and examples are blocks of text consisting of one or more
whole paragraphs that are set off from the bulk of the text and
treated differently.  They are usually indented in the output.

@findex end
In Texinfo, you always begin a quotation or example by writing an
@@-command at the beginning of a line by itself, and end it by writing
an @code{@@end} command that is also at the beginning of a line by
itself.  For instance, you begin an example by writing
@code{@@example} by itself at the beginning of a line and end the
example by writing @code{@@end example} on a line by itself, at the
beginning of that line, and with only one space between the
@code{@@end} and the @code{example}.

@menu
* Block Enclosing Commands::    Different constructs for different purposes.
* @code{@@quotation}::                  Writing a quotation.
* @code{@@indentedblock}::              Block of text indented on left.
* @code{@@example}::                    Writing an example in a fixed-width font.
* @code{@@verbatim}::                   Writing a verbatim example.
* @code{@@lisp}::                       Illustrating Lisp code.
* @code{@@display}::                    Writing an example in the current font.
* @code{@@format}::                     Writing an example without narrowed margins.
* @code{@@exdent}::                     Undo indentation on a line.
* @code{@@flushleft @@flushright}::      Pushing text flush left or flush right.
* @code{@@raggedright}::                Avoiding justification on the right.
* @code{@@noindent}::                   Preventing paragraph indentation.
* @code{@@indent}::                     Forcing paragraph indentation.
* @code{@@cartouche}::                  Drawing rounded rectangles around text.
* @code{@@small@dots{}}::                   Examples in a smaller font.
@end menu

@node Block Enclosing Commands
@section Block Enclosing Commands

Here is a summary of commands that enclose blocks of text, also known
as @dfn{environments}.  They're explained further in the following
sections.

@table @code
@item @@quotation
Indicate text that is quoted. The text is filled, indented (from both
margins), and printed in a roman font by default.

@item @@indentedblock
Like @code{@@quotation}, but the text is indented only on the left.

@item @@example
Illustrate code, commands, and the like. The text is printed
in a fixed-width font, and indented but not filled.

@item @@lisp
Like @code{@@example}, but specifically for illustrating Lisp code. The
text is printed in a fixed-width font, and indented but not filled.

@item @@verbatim
Mark a piece of text that is to be printed verbatim; no character
substitutions are made and all commands are ignored, until the next
@code{@@end verbatim}.  The text is printed in a fixed-width font,
and not indented or filled.  Extra spaces and blank lines are
significant, and tabs are expanded.

@item @@display
Display illustrative text.  The text is indented but not filled, and
no font is selected (so, by default, the font is roman).

@item @@format
Like @code{@@display} (the text is not filled and no font is
selected), but the text is not indented.

@item @@smallquotation
@itemx @@smallindentedblock
@itemx @@smallexample
@itemx @@smalllisp
@itemx @@smalldisplay
@itemx @@smallformat
These @code{@@small...} commands are just like their non-small
counterparts, except that they output text in a smaller font size,
where possible.

@item @@flushleft
@itemx @@flushright
Text is not filled, but is set flush with the left or right margin,
respectively.

@item @@raggedright
Text is filled, but only justified on the left, leaving the right
margin ragged.

@item @@cartouche
Highlight text, often an example or quotation, by drawing a box with
rounded corners around it.
@end table

The @code{@@exdent} command is used within the above constructs to
undo the indentation of a line.

The @code{@@noindent} command may be used after one of the above
constructs (or at the beginning of any paragraph) to prevent the
following text from being indented as a new paragraph.

@node @code{@@quotation}
@section @code{@@quotation}: Block Quotations
@anchor{quotation}@c old name

@cindex Quotations
@findex quotation

The text of a quotation is processed like normal text (regular font,
text is filled) except that:

@itemize @bullet
@item
both the left and right margins are closer to the center of the page,
so the whole of the quotation is indented;

@item
the first lines of paragraphs are indented no more than other lines; and

@item
an @code{@@author} command may be given to specify the author of the
quotation.
@end itemize

@quotation
This is an example of text written between a @code{@@quotation}
command and an @code{@@end quotation} command.  A @code{@@quotation}
command is most often used to indicate text that is excerpted from
another (real or hypothetical) printed work.
@end quotation

Write a @code{@@quotation} command as text on a line by itself.  This
line will disappear from the output.  Mark the end of the quotation
with a line beginning with and containing only @code{@@end quotation}.
The @code{@@end quotation} line will likewise disappear from the
output.

@code{@@quotation} takes one optional argument, given on the remainder
of the line.  This text, if present, is included at the beginning of
the quotation in bold or otherwise emphasized, and followed with a
@samp{:}.  For example:

@example
@@quotation Note
This is
a foo.
@@end quotation
@end example

@noindent
produces

@quotation Note
This is
a foo.
@end quotation

If the @code{@@quotation} argument is one of these English words
(case-insensitive):

@example
Caution  Important  Note  Tip  Warning
@end example

@cindex @code{<caution>} Docbook tag
@cindex @code{<important>} Docbook tag
@cindex @code{<note>} Docbook tag
@cindex @code{<tip>} Docbook tag
@cindex @code{<warning>} Docbook tag
@cindex @code{<blockquote>} HTML tag
@noindent then the Docbook output uses corresponding special tags
(@code{<note>}, etc.)@: instead of the default @code{<blockquote>}.
HTML output always uses @code{<blockquote>}.

If the author of the quotation is specified in the @code{@@quotation}
block with the @code{@@author} command, a line with the author name is
displayed after the quotation:

@example
@@quotation
People sometimes ask me if it is a sin in the Church of Emacs to use
vi.  Using a free version of vi is not a sin; it is a penance.  So happy
hacking.

@@author Richard Stallman
@@end quotation
@end example

@noindent
produces

@quotation
People sometimes ask me if it is a sin in the Church of Emacs to use
vi.  Using a free version of vi is not a sin; it is a penance.  So happy
hacking.

@author Richard Stallman
@end quotation

@findex smallquotation
Texinfo also provides a command @code{@@smallquotation}, which is just
like @code{@@quotation} but uses a smaller font size where possible.
@xref{@code{@@small@dots{}}}.

@node @code{@@indentedblock}
@section @code{@@indentedblock}: Indented text blocks
@cindex Indented text block
@findex indentedblock

The @code{@@indentedblock} environment is similar to
@code{@@quotation}, except that text is only indented on the left (and
there is no optional argument for an author).  Thus, the text font
remains unchanged, and text is gathered and filled as usual, but the
left margin is increased.  For example:

@indentedblock
This is an example of text written between an @code{@@indentedblock}
command and an @code{@@end indentedblock} command.  The
@code{@@indentedblock} environment can contain any text or other
commands desired.
@end indentedblock

This is written in the Texinfo source as:

@example
@@indentedblock
This is an example ...
@@end indentedblock
@end example

@findex smallindentedblock
Texinfo also provides a command @code{@@smallindentedblock}, which is
just like @code{@@indentedblock} but uses a smaller font size where
possible.  @xref{@code{@@small@dots{}}}.

@node @code{@@example}
@section @code{@@example}: Example Text

@anchor{example}@c old name
@findex example
@cindex Examples, formatting them
@cindex Formatting examples

The @code{@@example} environment is used to indicate an example that
is not part of the running text, such as computer input or output.
Write an @code{@@example} command at the beginning of a line by
itself.  Mark the end of the example with an @code{@@end example}
command, also written at the beginning of a line by itself.

An @code{@@example} environment has the following characteristics:

@itemize
@item Each line in the input file is a line in the output; that is,
the source text is not filled as it normally is.
@item Extra spaces and blank lines are significant.
@item The output is indented.
@item The output uses a fixed-width font.
@item Texinfo commands @emph{are} expanded; if you want the output to
be the input verbatim, use the @code{@@verbatim} environment instead
(@pxref{@code{@@verbatim}}).
@end itemize

For example,

@example
@@example
cp foo @@var@{dest1@}; \
 cp foo @@var@{dest2@}
@@end example
@end example

@noindent
produces

@example
cp foo @var{dest1}; \
 cp foo @var{dest2}
@end example

The lines containing @code{@@example} and @code{@@end example} will
disappear from the output.  To make the output look good, you should
put a blank line before the @code{@@example} and another blank line
after the @code{@@end example}.  Blank lines inside the beginning
@code{@@example} and the ending @code{@@end example}, on the other
hand, do appear in the output.

@quotation Caution
Do not use tabs in the lines of an example!  (Or anywhere else in
Texinfo, except in verbatim environments.)  @TeX{} treats tabs as
single spaces, and that is not what they look like.  In Emacs, you can
use @kbd{M-x untabify} to convert tabs in a region to multiple spaces.
@end quotation

Examples are often, logically speaking, ``in the middle'' of a
paragraph, and the text that continues afterwards should not be
indented, as in the example above.  The @code{@@noindent} command
prevents a piece of text from being indented as if it were a new
paragraph (@pxref{@code{@@noindent}}).

If you want to embed code fragments within sentences, instead of
displaying them, use the @code{@@code} command or its relatives
(@pxref{@code{@@code}}).

If you wish to write a ``comment'' on a line of an example in the
normal roman font, you can use the @code{@@r} command (@pxref{Fonts}).

@node @code{@@verbatim}
@section @code{@@verbatim}: Literal Text

@anchor{verbatim}@c old name
@findex verbatim
@cindex Verbatim environment

Use the @code{@@verbatim} environment for printing of text that may
contain special characters or commands that should not be interpreted,
such as computer input or output (@code{@@example} interprets its text
as regular Texinfo commands).  This is especially useful for including automatically
generated files in a Texinfo manual.

In general, the output will be just the same as the input.  No
character substitutions are made, e.g., all spaces and blank lines are
significant, including tabs.  In the printed manual, the text is
typeset in a fixed-width font, and not indented or filled.

Write a @code{@@verbatim} command at the beginning of a line by
itself.  This line will disappear from the output.  Mark the end of
the verbatim block with an @code{@@end verbatim} command, also written
at the beginning of a line by itself.  The @code{@@end verbatim} will
also disappear from the output.

For example:
@c oops, got to trick this a bit: can't use @end verbatim inside @verbatim

@example
@exdent @t{@@verbatim}
@exdent @t{@{}
@exdent @key{TAB}@t{@@command with strange characters: @@'e}
@exdent @t{expand@key{TAB}me}
@exdent @t{@}}
@exdent @t{@@end verbatim}
@end example

@noindent
This produces:

@verbatim
{
        @command with strange characters: @'e
expand	me
}
@end verbatim

Since the lines containing @code{@@verbatim} and @code{@@end verbatim}
produce no output, typically you should put a blank line before the
@code{@@verbatim} and another blank line after the @code{@@end
verbatim}.  Blank lines between the beginning @code{@@verbatim} and
the ending @code{@@end verbatim} will appear in the output.

@cindex Verbatim, small
@cindex Small verbatim
You can get a ``small'' verbatim by enclosing the @code{@@verbatim} in
an @code{@@smallformat} environment, as shown here:

@c more cheating ...
@smallexample
@exdent @t{@@smallformat}
@exdent @t{@@verbatim}
@exdent @t{... still verbatim, but in a smaller font ...}
@exdent @t{@@end verbatim}
@exdent @t{@@end smallformat}
@end smallexample

Finally, a word of warning: it is not reliable to use
@code{@@verbatim} inside other Texinfo constructs.

See also @ref{@code{@@verbatiminclude}}.

@node @code{@@lisp}
@section @code{@@lisp}: Marking a Lisp Example

@anchor{lisp}@c old name
@findex lisp
@cindex Lisp example

The @code{@@lisp} command is used for Lisp code.  It is synonymous
with the @code{@@example} command.

@lisp
This is an example of text written between an
@code{@@lisp} command and an @code{@@end lisp} command.
@end lisp

Use @code{@@lisp} instead of @code{@@example} to preserve information
regarding the nature of the example.  This is useful, for example, if
you write a function that evaluates only and all the Lisp code in a
Texinfo file.  Then you can use the Texinfo file as a Lisp
library.  Mark the end of @code{@@lisp} with @code{@@end lisp} on a line
by itself.

@node @code{@@display}
@section @code{@@display}: Examples Using the Text Font

@anchor{display}@c old name
@findex display
@cindex Display formatting

The @code{@@display} command begins another kind of environment, where
the font is left unchanged, not switched to typewriter as with
@code{@@example}.  Each line of input still produces a line of output,
and the output is still indented.

@display
This is an example of text written between a @code{@@display} command
and an @code{@@end display} command.  The @code{@@display} command
indents the text, but does not fill it.
@end display

@findex smalldisplay
Texinfo also provides the environment @code{@@smalldisplay}, which is
like @code{@@display} but uses a smaller font size.
@xref{@code{@@small@dots{}}}.

@node @code{@@format}
@section @code{@@format}: Examples Using the Full Line Width

@anchor{format}@c old name
@findex format

The @code{@@format} command is similar to @code{@@display}, except it
leaves the text unindented.  Like @code{@@display}, it does not select
the fixed-width font.

@format
This is an example of text written between a @code{@@format} command
and an @code{@@end format} command.  As you can see
from this example,
the @code{@@format} command does not fill the text.
@end format

@findex smallformat
Texinfo also provides the environment @code{@@smallformat}, which is
like @code{@@format} but uses a smaller font size.
@xref{@code{@@small@dots{}}}.

@node @code{@@exdent}
@section @code{@@exdent}: Undoing a Line's Indentation

@anchor{exdent}@c old name
@findex exdent
@cindex Indentation undoing

The @code{@@exdent} command removes any indentation a line might have.
The command is written at the beginning of a line and applies only to
the text that follows the command that is on the same line.  Do not use
braces around the text.  In a printed manual, the text on an
@code{@@exdent} line is printed in the roman font.

@code{@@exdent} is usually used within examples.  Thus,

@example
@group
@@example
This line follows an @@@@example command.
@@exdent This line is exdented.
This line follows the exdented line.
The @@@@end example comes on the next line.
@@end example
@end group
@end example

@noindent
produces

@example
@group
This line follows an @@example command.
@exdent This line is exdented.
This line follows the exdented line.
The @@end example comes on the next line.
@end group
@end example

In practice, the @code{@@exdent} command is rarely used.  Usually, you
un-indent text by ending the example and returning the page to its
normal width.

@code{@@exdent} has no effect in HTML output.

@node @code{@@flushleft @@flushright}
@section @code{@@flushleft} and @code{@@flushright}

@anchor{flushleft & flushright}@c old name
@findex flushleft
@findex flushright
@cindex Ragged right, without filling
@cindex Ragged left, without filling

The @code{@@flushleft} and @code{@@flushright} commands line up the
ends of lines on the left and right margins of a page,
but do not fill the text.  The commands are written on lines of their
own, without braces.  The @code{@@flushleft} and @code{@@flushright}
commands are ended by @code{@@end flushleft} and @code{@@end
flushright} commands on lines of their own.

@need 1500
For example,

@example
@group
@@flushleft
This text is
written flushleft.
@@end flushleft
@end group
@end example

@noindent
produces

@quotation
@flushleft
This text is
written flushleft.
@end flushleft
@end quotation

@code{@@flushright} produces the type of indentation often used in the
return address of letters.  For example,

@example
@group
@@flushright
Here is an example of text written
flushright.  The @@code@{@@flushright@} command
right justifies every line but leaves the
left end ragged.
@@end flushright
@end group
@end example

@noindent
produces

@flushright
Here is an example of text written
flushright.  The @code{@@flushright} command
right justifies every line but leaves the
left end ragged.
@end flushright

@node @code{@@raggedright}
@section @code{@@raggedright}: Ragged Right Text

@anchor{raggedright}@c old name
@findex raggedright
@cindex Ragged right, with filling

The @code{@@raggedright} fills text as usual, but the text is only
justified on the left; the right margin is ragged.  The command is
written on a line of its own, without braces.  The
@code{@@raggedright} command is ended by @code{@@end raggedright} on a
line of its own.  This command has no effect in Info and HTML output,
where text is always set ragged right.

The @code{@@raggedright} command can be useful with paragraphs
containing lists of commands with long names, when it is known in
advance that justifying the text on both margins will make the
paragraph look bad.

An example (from elsewhere in this manual):

@example
@group
@@raggedright
Commands for double and single angle quotation marks:
@@code@{@@@@guillemetleft@@@{@@@}@}, @@code@{@@@@guillemetright@@@{@@@}@},
@@code@{@@@@guillemotleft@@@{@@@}@}, @@code@{@@@@guillemotright@@@{@@@}@},
@@code@{@@@@guilsinglleft@@@{@@@}@}, @@code@{@@@@guilsinglright@@@{@@@}@}.
@@end raggedright
@end group
@end example

@noindent
produces

@raggedright
Commands for double and single angle quotation marks:
@code{@@guillemetleft@{@}}, @code{@@guillemetright@{@}},
@code{@@guillemotleft@{@}}, @code{@@guillemotright@{@}},
@code{@@guilsinglleft@{@}}, @code{@@guilsinglright@{@}}.
@end raggedright

@node @code{@@noindent}
@section @code{@@noindent}: Omitting Indentation

@anchor{noindent}@c old name
@findex noindent
@cindex Omitting indentation
@cindex Suppressing indentation
@cindex Indentation, omitting

An example or other inclusion can break a paragraph into segments.
Ordinarily, the formatters indent text that follows an example as a new
paragraph.  You can prevent this on a case-by-case basis by writing
@code{@@noindent} at the beginning of a line, preceding the continuation
text.  You can also disable indentation for all paragraphs globally with
@code{@@paragraphindent} (@pxref{@code{@@paragraphindent}}).

Here is an example showing how to eliminate the normal indentation of
the text after an @code{@@example}, a common situation:

@example
@group
@@example
This is an example
@@end example

@@noindent
This line is not indented.  As you can see, the
beginning of the line is fully flush left with the
line that follows after it.
@end group
@end example

@noindent produces:

@display
@example
This is an example
@end example

@noindent
This line is not indented.  As you can see, the
beginning of the line is fully flush left with the
line that follows after it.
@end display

The standard usage of @code{@@noindent} is just as above: at the
beginning of what would otherwise be a paragraph, to eliminate the
indentation that normally happens there.  It can either be followed by
text or be on a line by itself.  There is no reason to use it
in other contexts, such as in the middle of a paragraph or inside an
environment (@pxref{Quotations and Examples}).

You can control the number of blank lines in the Info file output by
adjusting the input as desired: a line containing just
@code{@@noindent} does not generate a blank line, and neither does an
@code{@@end} line for an environment.

Do not put braces after a @code{@@noindent} command; they are not
used, since @code{@@noindent} is a command used outside of paragraphs
(@pxref{Command Syntax}).

@node @code{@@indent}
@section @code{@@indent}: Forcing Indentation

@anchor{indent}@c old name
@findex indent
@cindex Forcing indentation
@cindex Inserting indentation
@cindex Indentation, forcing

@indent
To complement the @code{@@noindent} command (see the previous
section), Texinfo provides the @code{@@indent} command to force a
paragraph to be indented.  For instance, this paragraph (the first in
this section) is indented using an @code{@@indent} command.

And indeed, the first paragraph of a section is the most likely place
to use @code{@@indent}, to override the normal behavior of no
indentation there (@pxref{@code{@@paragraphindent}}).  It can either be
followed by text or be on a line by itself.

As a special case, when @code{@@indent} is used in an environment
where text is not filled, it produces a paragraph indentation space in
the @TeX{} output.  (These environments are where a line of input
produces a line of output, such as @code{@@example} and
@code{@@display}; for a summary of all environments, @pxref{Block
Enclosing Commands}.)

Do not put braces after an @code{@@indent} command; they are not used,
since @code{@@indent} is a command used outside of paragraphs
(@pxref{Command Syntax}).

@node @code{@@cartouche}
@section @code{@@cartouche}: Rounded Rectangles

@anchor{cartouche}@c old name
@findex cartouche
@cindex Box with rounded corners
@cindex Rounded rectangles, around text

In a printed manual, the @code{@@cartouche} command draws a box with
rounded corners around its contents.  In HTML, a normal rectangle is
drawn.  @code{@@cartouche} has no effect in Info output.

You can use this command to further highlight an example or quotation.
For instance, you could write a manual in which one type of example is
surrounded by a cartouche for emphasis.

For example,

@example
@@cartouche
@@example
% pwd
/usr/local/share/emacs
@@end example
@@end cartouche
@end example

@noindent
surrounds the two-line example with a box with rounded corners, in the
printed manual.

The output from the example looks like this (if you're reading this in
Info, you'll see the @code{@@cartouche} had no effect):

@cartouche
@example
% pwd
/usr/local/share/emacs
@end example
@end cartouche

@code{@@cartouche} also implies @code{@@group} (@pxref{@code{@@group}}).

@node @code{@@small@dots{}}
@section @code{@@small@dots{}} Block Commands

@anchor{small}@c old name
@findex smallexample
@findex smallformat
@findex smalllisp
@findex smallquotation
@cindex Small examples
@cindex Examples in smaller fonts
@cindex Quotations in smaller fonts
@cindex Lisp examples in smaller fonts

In addition to the regular @code{@@example} and similar commands,
Texinfo has ``small'' example-style commands.  These are
@code{@@smallquotation}, @code{@@smallindentedblock},
@code{@@smalldisplay}, @code{@@smallexample}, @code{@@smallformat},
and @code{@@smalllisp}.

In Info output, the @code{@@small@dots{}} commands are equivalent to
their non-small companion commands.

In @TeX{}, however, the @code{@@small@dots{}} commands typeset text in
a smaller font than the non-small example commands.  Thus, for
instance, code examples can contain longer lines and still fit on a
page without needing to be rewritten.

A smaller font size is also requested in HTML output, and (as usual)
retained in the Texinfo@tie{}XML transliteration.

Mark the end of a @code{@@small@dots{}} block with a corresponding
@code{@@end small@dots{}}.  For example, pair @code{@@smallexample} with
@code{@@end smallexample}.

Here is an example of the font used by the @code{@@smallexample}
command (in Info, the output will be the same as usual):

@smallexample
@dots{} to make sure that you have the freedom to
distribute copies of free software (and charge for
this service if you wish), that you receive source
code or can get it if you want it, that you can
change the software or use pieces of it in new free
programs; and that you know you can do these things.
@end smallexample

The @code{@@small@dots{}} commands use the same font style as their
normal counterparts: @code{@@smallexample} and @code{@@smalllisp} use
a fixed-width font, and everything else uses the regular font.
They also have the same behavior in other respects---whether filling
is done and whether margins are narrowed.

As a general rule, a printed document looks better if you use only one
of (for instance) @code{@@example} or @code{@@smallexample}
consistently within a chapter.

@node Lists and Tables
@chapter Lists and Tables
@cindex Making lists and tables
@cindex Lists and tables, making
@cindex Tables and lists, making

Texinfo has several ways of making lists and tables.  Lists can be
bulleted or numbered; two-column tables can highlight the items in
the first column; multi-column tables are also supported.

@menu
* Introducing Lists::           Texinfo formats lists for you.
* @code{@@itemize}::                    How to construct a simple list.
* @code{@@enumerate}::                  How to construct a numbered list.
* Two-column Tables::           How to construct a two-column table.
* Multi-column Tables::         How to construct generalized tables.
@end menu

@node Introducing Lists
@section Introducing Lists

Texinfo automatically indents the text in lists or tables, and numbers
an enumerated list.  This last feature is useful if you modify the
list, since you do not need to renumber it yourself.

Numbered lists and tables begin with the appropriate @@-command at the
beginning of a line, and end with the corresponding @code{@@end}
command on a line by itself.  The table and itemized-list commands
also require that you write formatting information on the same line as
the beginning @@-command.

Begin an enumerated list, for example, with an @code{@@enumerate}
command and end the list with an @code{@@end enumerate} command.
Begin an itemized list with an @code{@@itemize} command, followed on
the same line by a formatting command such as @code{@@bullet}, and end
the list with an @code{@@end itemize} command.
@findex end

Precede each element of a list with an @code{@@item} or @code{@@itemx}
command.

@sp 1
@noindent
Here is an itemized list of the different kinds of table and lists:

@itemize @bullet
@item
Itemized lists with and without bullets.

@item
Enumerated lists, using numbers or letters.

@item
Two-column tables with highlighting.
@end itemize

@sp 1
@noindent
Here is an enumerated list with the same items:

@enumerate
@item
Itemized lists with and without bullets.

@item
Enumerated lists, using numbers or letters.

@item
Two-column tables with highlighting.
@end enumerate

@sp 1
@noindent
And here is a two-column table with the same items and their
@w{@@-commands}:

@table @code
@item @@itemize
Itemized lists with and without bullets.

@item @@enumerate
Enumerated lists, using numbers or letters.

@item @@table
@itemx @@ftable
@itemx @@vtable
Two-column tables, optionally with indexing.
@end table

@node @code{@@itemize}
@section @code{@@itemize}: Making an Itemized List

@anchor{itemize}@c old name
@findex itemize
@cindex Itemization

The @code{@@itemize} command produces a sequence of ``items'', each
starting with a bullet or other mark inside the left margin, and
generally indented.

@cindex @code{@@w}, for blank items
Begin an itemized list by writing @code{@@itemize} at the beginning of
a line.  Follow the command, on the same line, with a character or a
Texinfo command that generates a mark.  Usually, you will use
@code{@@bullet} after @code{@@itemize}, but you can use
@code{@@minus}, or any command or character that results in a single
character in the Info file.  (When you write the mark command such as
@code{@@bullet} after an @code{@@itemize} command, you may omit the
@samp{@{@}}.)  If you don't specify a mark command, the default is
@code{@@bullet}.  If you don't want any mark at all, but still want
logical items, use @code{@@w@{@}} (in this case the braces are
required).

@findex item
After the @code{@@itemize}, write your items, each starting with
@code{@@item}.  Text can follow on the same line as the @code{@@item}.
The text of an item can continue for more than one paragraph.

There should be at least one @code{@@item} inside the @code{@@itemize}
environment.  If none are present, @code{makeinfo} gives a warning.
If you just want indented text and not a list of items, use
@code{@@indentedblock}; @pxref{@code{@@indentedblock}}.

Index entries and comments that are given before an @code{@@item}
including the first, are automatically moved (internally) to after the
@code{@@item}, so the output is as expected.  Historically this has
been a common practice.

Usually, you should put a blank line between items.  This puts a blank
line in the Info file. (@TeX{} inserts the proper vertical space in
any case.)  Except when the entries are very brief, these blank lines
make the list look better.

Here is an example of the use of @code{@@itemize}, followed by the
output it produces.  @code{@@bullet} produces an @samp{*} in Info and
a round dot in other output formats.

@example
@group
@@itemize @@bullet
@@item
Some text for foo.

@@item
Some text
for bar.
@@end itemize
@end group
@end example

@noindent
This produces:

@quotation
@itemize @bullet
@item
Some text for foo.

@item
Some text
for bar.
@end itemize
@end quotation

Itemized lists may be embedded within other itemized lists.  Here is a
list marked with dashes embedded in a list marked with bullets:

@example
@group
@@itemize @@bullet
@@item
First item.

@@itemize @@minus
@@item
Inner item.

@@item
Second inner item.
@@end itemize

@@item
Second outer item.
@@end itemize
@end group
@end example

@noindent
This produces:

@quotation
@itemize @bullet
@item
First item.

@itemize @minus
@item
Inner item.

@item
Second inner item.
@end itemize

@item
Second outer item.
@end itemize
@end quotation

@node @code{@@enumerate}
@section @code{@@enumerate}: Making a Numbered or Lettered List

@anchor{enumerate}@c old name
@findex enumerate
@cindex Enumeration

@code{@@enumerate} is like @code{@@itemize} (@pxref{@code{@@itemize}}),
except that the labels on the items are successive integers or letters
instead of bullets.

Write the @code{@@enumerate} command at the beginning of a line.  The
command does not require an argument, but accepts either a number or a
letter as an option.  Without an argument, @code{@@enumerate} starts the
list with the number @samp{1}.  With a numeric argument, such as
@samp{3}, the command starts the list with that number.  With an upper-
or lowercase letter, such as @samp{a} or @samp{A}, the command starts
the list with that letter.

Write the text of the enumerated list in the same way as an itemized
list: write a line starting with @code{@@item} at the beginning of
each item in the enumeration.  It is ok to have text following the
@code{@@item}, and the text for an item can continue for several
paragraphs.

You should put a blank line between entries in the list.
This generally makes it easier to read the Info file.

@need 1500
Here is an example of @code{@@enumerate} without an argument:

@example
@group
@@enumerate
@@item
Underlying causes.

@@item
Proximate causes.
@@end enumerate
@end group
@end example

@noindent
This produces:

@enumerate
@item
Underlying causes.

@item
Proximate causes.
@end enumerate
@sp 1
Here is an example with an argument of @kbd{3}:
@sp 1
@example
@group
@@enumerate 3
@@item
Predisposing causes.

@@item
Precipitating causes.

@@item
Perpetuating causes.
@@end enumerate
@end group
@end example

@noindent
This produces:

@enumerate 3
@item
Predisposing causes.

@item
Precipitating causes.

@item
Perpetuating causes.
@end enumerate
@sp 1
Here is a brief summary of the alternatives.  The summary is constructed
using @code{@@enumerate} with an argument of @kbd{a}.
@sp 1
@enumerate a
@item
@code{@@enumerate}

Without an argument, produce a numbered list, with the first item
numbered@tie{}1.

@item
@code{@@enumerate @var{unsigned-integer}}

With an (unsigned) numeric argument, start a numbered list with that
number.  You can use this to continue a list that you interrupted with
other text.

@item
@code{@@enumerate @var{upper-case-letter}}

With an uppercase letter as argument, start a list
in which each item is marked
by a letter, beginning with that uppercase letter.

@item
@code{@@enumerate @var{lower-case-letter}}

With a lowercase letter as argument, start a list
in which each item is marked by
a letter, beginning with that lowercase letter.
@end enumerate

You can also nest enumerated lists, as in an outline.

@node Two-column Tables
@section Making a Two-column Table

@cindex Tables, making two-column
@findex table

@code{@@table} is similar to @code{@@itemize}
(@pxref{@code{@@itemize}}), but allows you to specify a name or
heading line for each item.  The @code{@@table} command is used to
produce two-column tables, and is especially useful for glossaries,
explanatory exhibits, and command-line option summaries.

@menu
* @code{@@table}::                      How to construct a two-column table.
* @code{@@ftable @@vtable}::             Automatic indexing for two-column tables.
* @code{@@itemx}::                      How to put more entries in the first column.
@end menu

@node @code{@@table}
@subsection Using the @code{@@table} Command

@anchor{table}@c old name

@cindex Definition lists, typesetting
Use the @code{@@table} command to produce a two-column table.  This
command is typically used when you have a list of items and a brief text
with each one, such as a list of definitions.

Write the @code{@@table} command at the beginning of a line, after a
blank line, and follow it on the same line with an argument that is an
`indicating' command, such as @code{@@code}, @code{@@samp},
@code{@@var}, @code{@@option}, or @code{@@kbd} (@pxref{Indicating}).
This command will be applied to the text in the first column.  For
example, @code{@@table @@code} will cause the text in the first column
to be output as if it had been the argument to a @code{@@code} command.

@anchor{@code{@@asis}}@c command name with @, for consistency
@findex asis
You may use the @code{@@asis} command as an argument to
@code{@@table}.  @code{@@asis} is a command that does nothing: if you
use this command after @code{@@table}, the first column entries are
output without added highlighting (``as is'').

The @code{@@table} command works with other commands besides those
explicitly mentioned here.  However, you can only use predefined
Texinfo commands that take an argument in braces.  You cannot
reliably use a new command defined with @code{@@macro}, although an
@code{@@alias} (for a suitable predefined command) is acceptable.
@xref{Defining New Texinfo Commands}.

@findex item
Begin each table entry with an @code{@@item} command at the beginning
of a line.  Write the text for the first column on the same line as the
@code{@@item} command.  Write the text for the second column on the line
following the @code{@@item} line and on subsequent lines.  You may
write as many lines of supporting text as you wish, even several
paragraphs.  But only the text on the same line as the @code{@@item}
will be placed in the first column (including any footnotes).
You do not need to type anything for an empty second column.

Normally, you should put a blank line before an @code{@@item} line
(except the first one).  This puts a blank line in the Info file.
Except when the entries are very brief, a blank line looks better.
End the table with a line consisting of @code{@@end table}, followed
by a blank line.  @TeX{} will always start a new paragraph after the
table, so the blank line is needed for the Info output to be analogous.

@need 1500
For example, the following table highlights the text in the first
column with the @code{@@samp} command:

@example
@group
@@table @@samp
@@item foo
This is the text for
@@samp@{foo@}.

@@item bar
Text for @@samp@{bar@}.
@@end table
@end group
@end example

@noindent
This produces:

@table @samp
@item foo
This is the text for
@samp{foo}.
@item bar
Text for @samp{bar}.
@end table

If you want to list two or more named items with a single block of
text, use the @code{@@itemx} command.  (@xref{@code{@@itemx}}.)

The @code{@@table} command (@pxref{@code{@@table}}) is not supported
inside @code{@@display}.  Since @code{@@display} is line-oriented, it
doesn't make sense to use them together.  If you want to indent a
table, try @code{@@quotation} (@pxref{@code{@@quotation}}) or
@code{@@indentedblock} (@pxref{@code{@@indentedblock}}).

@node @code{@@ftable @@vtable}
@subsection @code{@@ftable} and @code{@@vtable}

@anchor{ftable vtable}@c old name
@findex ftable
@findex vtable
@cindex Tables with indexing
@cindex Indexing table entries automatically

The @code{@@ftable} and @code{@@vtable} commands are the same as the
@code{@@table} command except that @code{@@ftable} automatically enters
each of the items in the first column of the table into the index of
functions and @code{@@vtable} automatically enters each of the items in
the first column of the table into the index of variables.  This
simplifies the task of creating indices.  Only the items on the same
line as the @code{@@item} or @code{@@itemx} commands are indexed, and
they are indexed in exactly the form that they appear on that line.
@xref{Indices}, for more information about indices.

Begin a two-column table using @code{@@ftable} or @code{@@vtable} by
writing the @@-command at the beginning of a line, followed on the same
line by an argument that is a Texinfo command such as @code{@@code},
exactly as you would for a @code{@@table} command; and end the table
with an @code{@@end ftable} or @code{@@end vtable} command on a line by
itself.

See the example for @code{@@table} in the previous section.

@node @code{@@itemx}
@subsection @code{@@itemx}: Second and Subsequent Items

@anchor{itemx}@c old name
@cindex Two named items for @code{@@table}
@findex itemx

Use the @code{@@itemx} command inside a table when you have two or more
first column entries for the same item, each of which should appear on a
line of its own.

Use @code{@@item} for the first entry, and @code{@@itemx} for all
subsequent entries; @code{@@itemx} must always follow an @code{@@item}
command, with no blank line intervening.

The @code{@@itemx} command works exactly like @code{@@item} except
that it does not generate extra vertical space above the first column
text.  If you have multiple consecutive @code{@@itemx} commands, do
not insert any blank lines between them.

For example,

@example
@group
@@table @@code
@@item upcase
@@itemx downcase
These two functions accept a character or a string as
argument, and return the corresponding uppercase (lowercase)
character or string.
@@end table
@end group
@end example

@noindent
This produces:

@table @code
@item upcase
@itemx downcase
These two functions accept a character or a string as
argument, and return the corresponding uppercase (lowercase)
character or string.
@end table

@noindent
(Note also that this example illustrates multi-line supporting text in
a two-column table.)

@node Multi-column Tables
@section @code{@@multitable}: Multi-column Tables

@findex multitable
@cindex Tables, making multi-column

@code{@@multitable} allows you to construct tables with any number of
columns, with each column having any width you like.

You define the column widths on the @code{@@multitable} line itself, and
write each row of the actual table following an @code{@@item} command,
with columns separated by a @code{@@tab} command.  Finally, @code{@@end
multitable} completes the table.  Details in the sections below.

@menu
* Multitable Column Widths::    Defining multitable column widths.
* Multitable Rows::             Defining multitable rows, with examples.
@end menu

@node Multitable Column Widths
@subsection Multitable Column Widths
@cindex Multitable column widths
@cindex Column widths, defining for multitables
@cindex Widths, defining multitable column

You can define the column widths for a multitable in two ways: as
fractions of the line length; or with a prototype row.  Mixing the two
methods is not supported.  In either case, the widths are defined
entirely on the same line as the @code{@@multitable} command.

@enumerate
@item
@findex columnfractions
@cindex Line length, column widths as fraction of
To specify column widths as fractions of the line length, write
@code{@@columnfractions} and the decimal numbers (presumably less than
1; a leading zero is allowed and ignored) after the
@code{@@multitable} command, as in:

@example
@@multitable @@columnfractions .33 .33 .33
@end example

The fractions need not add up exactly to 1.0, as these do not.  This
allows you to produce tables that do not need the full line length.

@item
@cindex Prototype row, column widths defined by
To specify a prototype row, write the longest entry for each column
enclosed in braces after the @code{@@multitable} command.  For example:

@example
@@multitable @{some text for column one@} @{for column two@}
@end example

@noindent
The first column will then have the width of the typeset `some text for
column one', and the second column the width of `for column two'.

The prototype entries need not appear in the table itself.

Although we used simple text in this example, the prototype entries can
contain Texinfo commands; markup commands such as @code{@@code} are
particularly likely to be useful.

@end enumerate

@node Multitable Rows
@subsection Multitable Rows

@cindex Multitable rows
@cindex Rows, of a multitable

@findex item
@findex tab
After the @code{@@multitable} command defining the column widths (see
the previous section), you begin each row in the body of a multitable
with @code{@@item}, and separate the column entries with @code{@@tab}.
Line breaks are not special within the table body, and you may break
input lines in your source file as necessary.

@findex headitem
@cindex Heading row, in table
@cindex @code{<thead>} HTML/XML tag
You can also use @code{@@headitem} instead of @code{@@item} to produce
a @dfn{heading row}.  The @TeX{} output for such a row is in bold, and
the HTML and Docbook output uses the @code{<thead>} tag.  In Info, the
heading row is followed by a separator line made of dashes (@samp{-}
characters).

@findex headitemfont
@cindex Font for multitable heading rows
The command @code{@@headitemfont} can be used in templates when the
entries in a @code{@@headitem} row need to be used in a template.  It
is a synonym for @code{@@b}, but using @code{@@headitemfont} avoids
any dependency on that particular font style, in case we provide a way
to change it in the future.

Here is a complete example of a multi-column table (the text is from
@cite{The GNU Emacs Manual}, @pxref{Split Window,, Splitting Windows,
emacs, The GNU Emacs Manual}):

@example
@@multitable @@columnfractions .15 .45 .4
@@headitem Key @@tab Command @@tab Description
@@item C-x 2
@@tab @@code@{split-window-vertically@}
@@tab Split the selected window into two windows,
with one above the other.
@@item C-x 3
@@tab @@code@{split-window-horizontally@}
@@tab Split the selected window into two windows
positioned side by side.
@@item C-Mouse-2
@@tab
@@tab In the mode line or scroll bar of a window,
split that window.
@@end multitable
@end example

@noindent produces:

@multitable @columnfractions .15 .45 .4
@headitem Key @tab Command @tab Description
@item C-x 2
@tab @code{split-window-vertically}
@tab Split the selected window into two windows,
with one above the other.
@item C-x 3
@tab @code{split-window-horizontally}
@tab Split the selected window into two windows
positioned side by side.
@item C-Mouse-2
@tab
@tab In the mode line or scroll bar of a window,
split that window.
@end multitable

@node Special Displays
@chapter Special Displays
@cindex Special displays

The commands in this chapter allow you to write text that is specially
displayed (output format permitting), outside of the normal document
flow.

One set of such commands is for creating ``floats'', that is, figures,
tables, and the like, set off from the main text, possibly numbered,
captioned, and/or referred to from elsewhere in the document.  Images
are often included in these displays.

Another group of commands is for creating footnotes in Texinfo.

@menu
* Floats::                      Figures, tables, and the like.
* Images::                      Including graphics and images.
* Footnotes::                   Writing footnotes.
@end menu

@node Floats
@section Floats
@cindex Floats, in general

A @dfn{float} is a display which is set off from the main text.  It is
typically labeled as being a ``Figure'', ``Table'', ``Example'', or
some similar type.

@cindex Floating, not yet implemented
A float is so-named because, in principle, it can be moved to the
bottom or top of the current page, or to a following page, in the
printed output.  (Floating does not make sense in other output
formats.)  In the present version of Texinfo, however, this floating
is unfortunately not yet implemented.  Instead, the floating material
is simply output at the current location, more or less as if it were
an @code{@@group} (@pxref{@code{@@group}}).

@menu
* @code{@@float}::                      Producing floating material.
* @code{@@caption @@shortcaption}::      Specifying descriptions for floats.
* @code{@@listoffloats}::               A table of contents for floats.
@end menu

@node @code{@@float}
@subsection @code{@@float} [@var{type}][,@var{label}]: Floating Material

@anchor{float}@c old name
@findex float
@cindex Float environment

To produce floating material, enclose the material you want to be
displayed separate between @code{@@float} and @code{@@end float}
commands, on lines by themselves.

Floating material often uses @code{@@image} to display an
already-existing graphic (@pxref{Images}), or @code{@@multitable} to
display a table (@pxref{Multi-column Tables}).  However, the contents
of the float can be anything.  Here's an example with simple text:

@example
@@float Figure,fig:ex1
This is an example float.
@@end float
@end example

@noindent And the output:

@float Figure,fig:ex1
This is an example float.
@end float

As shown in the example, @code{@@float} takes two arguments (separated
by a comma), @var{type} and @var{label}.  Both are optional.

@table @var
@item type
Specifies the sort of float this is; typically a word such as
``Figure'', ``Table'', etc.  If this is not given, and @var{label} is,
any cross-referencing will simply use a bare number.

@item label
Specifies a cross-reference label for this float.  If given, this
float is automatically given a number, and will appear in any
@code{@@listoffloats} output (@pxref{@code{@@listoffloats}}).  Cross
references to @var{label} are allowed.

@cindex Floats, making unnumbered
@cindex Unnumbered float, creating
On the other hand, if @var{label} is not given, then the float will
not be numbered and consequently will not appear in the
@code{@@listoffloats} output or be cross-referenceable.
@end table

@noindent Ordinarily, you specify both @var{type} and @var{label}, to get a
labeled and numbered float.

@cindex Floats, numbering of
@cindex Numbering of floats
In Texinfo, all floats are numbered in the same way: with the chapter
number (or appendix letter), a period, and the float number, which
simply counts 1, 2, 3, @dots{}, and is reset at each chapter.  Each
float type is counted independently.

Floats within an @code{@@unnumbered}, or outside of any chapter, are
simply numbered consecutively from 1.

These numbering conventions are not, at present, changeable.

@node @code{@@caption @@shortcaption}
@subsection @code{@@caption} & @code{@@shortcaption}

@anchor{caption shortcaption}@c old name
@findex caption
@findex shortcaption
@cindex Captions, for floats
@cindex Short captions, for lists of floats

You may write a @code{@@caption} anywhere within a @code{@@float}
environment, to define a caption for the float.  It is not allowed in
any other context.  @code{@@caption} takes a single argument, enclosed
in braces.  Here's an example:

@example
@@float
An example float, with caption.
@@caption@{Caption for example float.@}
@@end float
@end example

@noindent The output is:

@float
An example float, with caption.
@caption{Caption for example float.}
@end float

@code{@@caption} can appear anywhere within the float; it is not
processed until the @code{@@end float}.  The caption text is usually a
sentence or two, but may consist of several paragraphs if necessary.

In the output, the caption always appears below the float; this is not
currently changeable.  It is preceded by the float type and/or number,
as specified to the @code{@@float} command (see the previous section).

The @code{@@shortcaption} command likewise may be used only within
@code{@@float}, and takes a single argument in braces.  The short
caption text is used instead of the caption text in a list of floats
(see the next section).  Thus, you can write a long caption for the
main document, and a short title to appear in the list of floats.  For
example:

@example
@@float
... as above ...
@@shortcaption@{Text for list of floats.@}
@@end float
@end example

The text for @code{@@shortcaption} may not contain comments
(@code{@@c}), verbatim text (@code{@@verb}), environments such as
@code{@@example}, footnotes (@code{@@footnote}) or other complex
constructs.  The same constraints apply to @code{@@caption} unless
there is a @code{@@shortcaption}.

@node @code{@@listoffloats}
@subsection @code{@@listoffloats}: Tables of Contents for Floats

@anchor{listoffloats}@c old name
@findex listoffloats
@cindex List of floats
@cindex Floats, list of
@cindex Table of contents, for floats

You can write a @code{@@listoffloats} command to generate a list of
floats for a given float type (@pxref{@code{@@float}}), analogous to
the document's overall table of contents.  Typically, it is written in
its own @code{@@unnumbered} node to provide a heading and structure,
rather like @code{@@printindex} (@pxref{Printing Indices & Menus}).

@code{@@listoffloats} takes one optional argument, the float type.
Here's an example:

@example
@@node List of Figures
@@unnumbered List of Figures
@@listoffloats Figure
@end example

@noindent And here's what the output from @code{@@listoffloats}
looks like, given the example figure earlier in this chapter (the Info
output is formatted as a menu):

@display
@ifinfo
*      Figure 12.1:      fig:ex1.
@end ifinfo
@ifnotinfo
@listoffloats Figure
@end ifnotinfo
@end display

Without any argument, @code{@@listoffloats} generates a list of floats
for which no float type was specified, i.e., no first argument to the
@code{@@float} command (@pxref{@code{@@float}}).

Each line in the list of floats contains the float type (if any),
the float number, and the caption, if any---the @code{@@shortcaption}
argument, if it was specified, else the @code{@@caption} argument.
In Info, the result is a menu where each float can be selected.  In
HTML, each line is a link to the float.  In printed output, the page
number is included.

Unnumbered floats (those without cross-reference labels) are omitted
from the list of floats.

@node Images
@section Inserting Images

@cindex Images, inserting
@cindex Pictures, inserting
@findex image

You can insert an image given in an external file with the
@code{@@image} command.  Although images can be used anywhere,
including the middle of a paragraph, we describe them in this chapter
since they are most often part of a displayed figure or example.

@menu
* Image Syntax::
* Image Scaling::
@end menu

@node Image Syntax
@subsection Image Syntax

Here is the synopsis of the @code{@@image} command:

@example
@@image@{@var{filename}@r{[,} @var{width}@r{[,} @var{height}@r{[,} @var{alttext}@r{[, }@var{extension}@r{]]]]}@}
@end example

@cindex Formats for images
@cindex Image formats
The @var{filename} argument is mandatory, and must not have an
extension, because the different processors support different formats:

@itemize @bullet
@item
@pindex eps image format
@TeX{} (DVI output) reads the file @file{@var{filename}.eps}
(Encapsulated PostScript format).

@item
@pindex pdftex@r{, and images}
@pindex png image format
@pindex jpeg image format
@pindex pdf image inclusions
pdf@TeX{} reads @file{@var{filename}.pdf}, @file{@var{filename}.png},
@file{@var{filename}.jpg}, or @file{@var{filename}.jpeg} (in that
order).  It also tries uppercase versions of the extensions.  The PDF
format does not support EPS images, so such must be converted first.

@item
For Info, @code{makeinfo} includes @file{@var{filename}.txt} verbatim
(more or less as if it were in @code{@@verbatim}).  The Info output
may also include a reference to @file{@var{filename}.png} or
@file{@var{filename}.jpg}.  (See below.)

@item
For HTML, @code{makeinfo} outputs a reference to
@file{@var{filename}.png}, @file{@var{filename}.jpg},
@file{@var{filename}.jpeg} or @file{@var{filename}.gif} (in that
order).  If none of those exist, it gives an error, and outputs a
reference to @file{@var{filename}.jpg} anyway.

@item
@cindex SVG images, used in Docbook
For Docbook, @code{makeinfo} outputs references to
@file{@var{filename}.eps}, @file{@var{filename}.gif}
@file{@var{filename}.jpeg}, @file{@var{filename}.jpg},
@file{@var{filename}.pdf}, @file{@var{filename}.png} and
@file{@var{filename}.svg}, for every file found.  Also,
@file{@var{filename}.txt} is included verbatim, if present.  (The
subsequent Docbook processor is supposed to choose the appropriate one.)

@item
For Info and HTML output, @code{makeinfo} uses the optional fifth
argument @var{extension} to @code{@@image} for the filename extension,
if it is specified and the file is found.  Any leading period should
be included in @var{extension}.  For example:

@pindex XPM image format
@example
@@image@{foo,,,,.xpm@}
@end example

@end itemize

If you want to install image files for use by Info readers too, we
recommend putting them in a subdirectory like @samp{@var{foo}-figures}
for a package @var{foo}.  Copying the files into
@code{$(infodir)/@var{foo}-figures/} should be done in your
@code{Makefile}.

The @var{width} and @var{height} arguments are described in the next
section.

For @TeX{} output, if an image is the only thing in a paragraph it
will ordinarily be displayed on a line by itself, respecting the
current environment indentation, but without the normal paragraph
indentation.  If you want it centered, use @code{@@center}
(@pxref{@code{@@titlefont @@center @@sp}}).

@cindex Alt attribute for images
@cindex Images, alternate text for
@findex @sortas{-} -@r{ (in image alt string)}
For HTML output, @code{makeinfo} sets the @dfn{alt attribute} for
inline images to the optional @var{alttext} (fourth) argument to
@code{@@image}, if supplied.  If not supplied, @code{makeinfo} uses
the full file name of the image being displayed.  The @var{alttext} is
processed as Texinfo text, so special characters such as @samp{"} and
@samp{<} and @samp{&} are escaped in the HTML output; also, you can
get an empty @code{alt} string with @code{@@-} (a command that
produces no output; @pxref{@code{@@- @@hyphenation}}).

For Info output, the @code{alt} string is also processed as Texinfo
text and output.  In this case, @samp{\} is escaped as @samp{\\} and
@samp{"} as @samp{\"}; no other escapes are done.

In Info output, @code{makeinfo} writes a reference to the binary image
file (trying @var{filename} suffixed with @file{@var{extension}},
@file{@var{.extension}}, @file{.png}, or @file{.jpg}, in that order)
if one exists.  It also literally includes the @file{.txt} file if one
exists.  This way, Info readers which can display images (such as the
Emacs Info browser, running under X) can do so, whereas Info readers
which can only use text (such as the standalone Info reader) can
display the textual version.

@cindex @samp{^@@^H} for images in Info
The implementation of this is to put the following construct into the
Info output:

@example
^@@^H[image src="@var{binaryfile}" text="@var{txtfile}"
           alt="@var{alttext} ... ^@@^H]
@end example

@noindent where @samp{^@@} and @samp{^H} stand for the actual null and
backspace control characters.  If one of the files is not present, the
corresponding argument is omitted.

The reason for mentioning this here is that older Info browsers (this
feature was introduced in Texinfo version 4.6) will display the above
literally, which, although not pretty, should not be harmful.

@node Image Scaling
@subsection Image Scaling

@cindex Images, scaling
@cindex Scaling images
@cindex Width of images
@cindex Height of images
@cindex Aspect ratio of images
@cindex Distorting images
The optional @var{width} and @var{height} arguments to the
@code{@@image} command (see the previous section) specify the size to
which to scale the image.  They are only taken into account in @TeX{}.
If neither is specified, the image is presented in its natural size
(given in the file); if only one is specified, the other is scaled
proportionately; and if both are specified, both are respected, thus
likely distorting the original image by changing its aspect ratio.

@cindex Dimensions and image sizes
The @var{width} and @var{height} may be specified using any valid @TeX{}
dimension, namely:

@table @asis
@item pt
@cindex Points (dimension)
point (72.27pt = 1in)
@item pc
@cindex Picas
pica (1pc = 12pt)
@item bp
@cindex Big points
big point (72bp = 1in)
@item in
@cindex Inches
inch
@item cm
@cindex Centimeters
centimeter (2.54cm = 1in)
@item mm
@cindex Millimeters
millimeter (10mm = 1cm)
@item dd
@cindex Did@^ot points
did@^ot point (1157dd = 1238pt)
@item cc
@cindex Ciceros
cicero (1cc = 12dd)
@item sp
@cindex Scaled points
scaled point (65536sp = 1pt)
@end table

@pindex ridt.eps
For example, the following will scale a file @file{ridt.eps} to one
inch vertically, with the width scaled proportionately:

@example
@@image@{ridt,,1in@}
@end example

@pindex epsf.tex
For @code{@@image} to work with @TeX{}, the file @file{epsf.tex} must be
installed somewhere that @TeX{} can find it.  (The standard location is
@file{@var{texmf}/tex/generic/dvips/epsf.tex}, where @var{texmf} is a
root of your @TeX{} directory tree.)  This file is included in the
Texinfo distribution and is also available from
@uref{ftp://tug.org/tex/epsf.tex}, among other places.

@code{@@image} can be used within a line as well as for displayed
figures.  Therefore, if you intend it to be displayed, be sure to leave
a blank line before the command, or the output will run into the
preceding text.

Image scaling is presently implemented only in @TeX{}, not in HTML or
any other sort of output.

@node Footnotes
@section Footnotes
@cindex Footnotes
@findex footnote

A @dfn{footnote} is for a reference that documents or elucidates the
primary text.@footnote{A footnote should complement or expand upon the
primary text, but a reader should not need to read a footnote to
understand the primary text.  For a thorough discussion of footnotes,
see @cite{The Chicago Manual of Style}, which is published by the
University of Chicago Press.}

Footnotes are distracting; use them sparingly at most, and it is best
to avoid them completely.  Standard bibliographical references are
usually better placed in a bibliography at the end of a document
instead of in footnotes throughout.

@menu
* Footnote Commands::           How to write a footnote in Texinfo.
* Footnote Styles::             Controlling how footnotes appear in Info.
@end menu

@node Footnote Commands
@subsection Footnote Commands

In Texinfo, footnotes are created with the @code{@@footnote} command.
This command is followed immediately by a left brace, then by the text
of the footnote, and then by a terminating right brace.  Footnotes may
be of any length (they will be broken across pages if necessary), but
are usually short.  The template is:

@example
ordinary text@@footnote@{@var{text of footnote}@}
@end example

As shown here, the @code{@@footnote} command should come right after the
text being footnoted, with no intervening space; otherwise, the footnote
marker might end up starting a line.

For example, this clause is followed by a sample footnote@footnote{Here
is the sample footnote.}; in the Texinfo source, it looks like
this:

@example
@dots{}a sample footnote@@footnote@{Here is the sample
footnote.@}; in the Texinfo source@dots{}
@end example

As you can see, this source includes two punctuation marks next to
each other; in this case, @samp{.@};} is the sequence.  This is normal
(the first ends the footnote and the second belongs to the sentence
being footnoted), so don't worry that it looks odd.  (Another style,
perfectly acceptable, is to put the footnote after punctuation
belonging to the sentence, as in @samp{;@@footnote@{...}.)

In a printed manual or book, the reference mark for a footnote is a
small, superscripted number; the text of the footnote appears at the
bottom of the page, below a horizontal line.

In Info, the reference mark for a footnote is a pair of parentheses
with the footnote number between them, like this: @samp{(1)}.  The
reference mark is followed by a cross-reference link to the footnote
text if footnotes are put in separate nodes (@pxref{Footnote Styles}).

In the HTML output, footnote references are generally marked with a
small, superscripted number which is rendered as a hypertext link to
the footnote text.

@cindex Critical editions
@cindex Nested footnotes
Footnotes cannot be nested, and cannot appear in section headings of
any kind or other ``unusual'' places.

A final tip: footnotes in the argument of an @code{@@item} command for
an @code{@@table} must be entirely on the same line as the
@code{@@item} (as usual).  @xref{Two-column Tables}.

@node Footnote Styles
@subsection Footnote Styles

Info has two footnote styles, which determine where the text of the
footnote is located:

@itemize @bullet
@cindex @samp{@r{End}} node footnote style
@item
In the `End' node style, all the footnotes for a single node are
placed at the end of that node.  The footnotes are separated from the
rest of the node by a line of dashes with the word @samp{Footnotes}
within it.  Each footnote begins with an @samp{(@var{n})} reference
mark.

@need 700
@noindent
Here is an example of the Info output for a single footnote in the
end-of-node style:

@example
@group
--------- Footnotes ---------

(1)  Here is a sample footnote.
@end group
@end example

@cindex @samp{@r{Separate}} footnote style
@item
In the `Separate' node style, all the footnotes for a single
node are placed in an automatically constructed node of
their own.  In this style, a ``footnote reference'' follows
each @samp{(@var{n})} reference mark in the body of the
node.  The footnote reference is actually a cross-reference
which you use to reach the footnote node.

The name of the node with the footnotes is constructed
by appending @w{@samp{-Footnotes}} to the name of the node
that contains the footnotes. (Consequently, the footnotes'
node for the @file{Footnotes} node is
@w{@file{Footnotes-Footnotes}}!)  The footnotes' node has an
`Up' node pointer that leads back to its parent node.

@noindent
Here is how the first footnote in this manual looks after being
formatted for Info in the separate node style:

@smallexample
@group
File: texinfo.info  Node: Overview-Footnotes, Up: Overview

(1) The first syllable of "Texinfo" is pronounced like "speck", not
"hex". @dots{}
@end group
@end smallexample
@end itemize

Unless your document has long and important footnotes (as in, say,
Gibbon's @cite{Decline and Fall @dots{}}), we recommend the @samp{end}
style, as it is simpler for readers to follow.

@findex footnotestyle
Use the @code{@@footnotestyle} command to specify an Info file's
footnote style.  Write this command at the beginning of a line followed
by an argument, either @samp{end} for the end node style or
@samp{separate} for the separate node style.

@need 700
For example,

@example
@@footnotestyle end
@end example
@noindent
or
@example
@@footnotestyle separate
@end example

Write a @code{@@footnotestyle} command before or shortly after the
end-of-header line at the beginning of a Texinfo file.  (You should
include any @code{@@footnotestyle} command between the start-of-header
and end-of-header lines, so the region formatting commands will format
footnotes as specified.)

In HTML, when the footnote style is @samp{end}, or if the output is
not split, footnotes are put at the end of the output.  If set to
@samp{separate}, and the output is split, they are placed in a
separate file.

@node Indices
@chapter Indices
@cindex Indices

Using Texinfo, you can generate indices without having to sort and
collate entries manually.  In an index, the entries are listed in
alphabetical order, together with information on how to find the
discussion of each entry.  In a printed manual, this information
consists of page numbers.  In an Info file, this information is a menu
entry leading to the first node referenced.

Texinfo provides several predefined kinds of index: an index for
functions, an index for variables, an index for concepts, and so on.
You can combine indices or use them for other than their canonical
purpose.  Lastly, you can define your own new indices.

@menu
* Predefined Indices::          Use different indices for different kinds
                                 of entries.
* Indexing Commands::           How to make an index entry.
* Index Entries::               Choose different words for index entries.
* Printing Indices & Menus::    How to print an index in hardcopy and
                                 generate index menus in Info.
* Combining Indices::           How to combine indices.
* New Indices::                 How to define your own indices.
@end menu

@node Predefined Indices
@section Predefined Indices

Texinfo provides six predefined indices.  Here are their nominal
meanings, abbreviations, and the corresponding index entry commands:

@table @samp
@item cp
@cindex @code{cp} (concept) index
@findex cindex
(@code{@@cindex}) concept index, for general concepts.
@item fn
@cindex @code{fn} (function) index
@findex findex
(@code{@@findex}) function index, for function and function-like
names (such as entry points of libraries).
@item ky
@cindex @code{ky} (keystroke) index
@findex kindex
(@code{@@kindex}) keystroke index, for keyboard commands.
@item pg
@cindex @code{pg} (program) index
@findex pindex
(@code{@@pindex}) program index, for names of programs.
@item tp
@cindex @code{tp} (data type) index
@findex tindex
(@code{@@tindex}) data type index, for type names (such as structures
defined in header files).
@item vr
@cindex @code{vr} (variable) index
@findex vindex
(@code{@@vindex}) variable index, for variable names (such as global
variables of libraries).
@end table

@noindent
Not every manual needs all of these, and most manuals use only two or
three at most.  The present manual, for example, has two indices: a
concept index and an @@-command index (that is actually the function
index but is called a command index in the chapter heading).

You are not required to use the predefined indices strictly for their
canonical purposes.  For example, suppose you wish to index some C
preprocessor macros.  You could put them in the function index along
with actual functions, just by writing @code{@@findex} commands for
them; then, when you print the ``Function Index'' as an unnumbered
chapter, you could give it the title `Function and Macro Index' and
all will be consistent for the reader.

On the other hand, it is best not to stray too far from the meaning of
the predefined indices.  Otherwise, in the event that your text is
combined with other text from other manuals, the index entries will
not match up.  Instead, define your own new index (@pxref{New
Indices}).

We recommend having a single index in the final document whenever
possible, however many source indices you use, since then readers have
only one place to look.  Two or more source indices can be combined
into one output index using the @code{@@synindex} or
@code{@@syncodeindex} commands (@pxref{Combining Indices}).

@node Indexing Commands
@section Defining the Entries of an Index

@cindex Defining indexing entries
@cindex Index entries
@cindex Entries for an index
@cindex Specifying index entries
@cindex Creating index entries

The data to make an index come from many individual indexing commands
scattered throughout the Texinfo source file.  Each command says to add
one entry to a particular index; after formatting, the index will give
the current page number or node name as the reference.

An index entry consists of an indexing command at the beginning of a
line followed, on the rest of the line, by the entry.

For example, this section begins with the following five entries for
the concept index:

@example
@@cindex Defining indexing entries
@@cindex Index entries, defining
@@cindex Entries for an index
@@cindex Specifying index entries
@@cindex Creating index entries
@end example

Each predefined index has its own indexing command---@code{@@cindex}
for the concept index, @code{@@findex} for the function index, and so
on, as listed in the previous section.

Index entries should precede the visible material that is being
indexed.  For instance:

@example
@@cindex hello
Hello, there!
@end example

@noindent Among other reasons, that way following indexing links (in
whatever context) ends up before the material, where readers want to
be, instead of after.

@cindex Index font types
By default, entries for a concept index are printed in a small roman
font and entries for the other indices are printed in a small
@code{@@code} font.  You may change the way part of an entry is
printed with the usual Texinfo commands, such as @code{@@file} for
file names (@pxref{Marking Text}), and @code{@@r} for the normal roman
font (@pxref{Fonts}).

@findex sortas
@cindex sort keys for index entries
@cindex index sorting
For the printed output, you may specify an explicit sort key for an
index entry using @code{@@sortas} immediately following the index
command.  For example: @samp{@@findex @@sortas@{\@} \ @@r@{(literal
\ in @@code@{@@@@math@})} sorts the index entry this produces under
backslash.

@vindex txiindexbackslashignore
@vindex txiindexhyphenignore
@vindex txiindexlessthanignore
@vindex txiindexatsignignore
To reduce the quantity of sort keys you need to provide explicitly,
you may choose to ignore certain characters in index entries
for the purposes of sorting.  The characters that you can
currently choose to ignore are @samp{\}, @samp{-}, @samp{<}
and @samp{@@}, which are ignored by giving as an argument to the
@code{@@set} command, respectively, @code{txiindexbackslashignore},
@code{txiindexhyphenignore}, @code{txiindexlessthanignore} and
@code{txiindexatsignignore}.  For example, specifying @samp{@@set
txiindexbackslashignore} causes the @samp{\mathopsup} entry in the
index for this manual to be sorted as if it were @samp{mathopsup},
so that it appears among the other entries beginning `M'.

@quotation Caution
Do not use a colon in an index entry.  In Info, a colon separates the
menu entry name from the node name, so a colon in the entry itself
confuses Info.  @xref{Menu Parts}, for more information about the
structure of a menu entry.
@end quotation

@node Index Entries
@section Making Index Entries
@cindex Index entries, making
@cindex Entries, making index

@cindex Writing index entries
@cindex Index entries, advice on writing
@cindex Advice on writing entries
@cindex Capitalization of index entries
Concept index entries consist of text.  The best way to write an index
is to devise entries which are terse yet clear.  If you can do this,
the index usually looks better if the entries are written just as they
would appear in the middle of a sentence, that is, capitalizing only
proper names and acronyms that always call for uppercase letters.
This is the case convention we use in most GNU manuals' indices.

If you don't see how to make an entry terse yet clear, make it longer
and clear---not terse and confusing.  If many of the entries are
several words long, the index may look better if you use a different
convention: to capitalize the first word of each entry.  Whichever
case convention you use, use it consistently.

In any event, do not ever capitalize a case-sensitive name such as a C
or Lisp function name or a shell command; that would be a spelling
error.  Entries in indices other than the concept index are symbol
names in programming languages, or program names; these names are
usually case-sensitive, so likewise use upper- and lowercase as
required.

@cindex Unique index entries
It is a good idea to make index entries unique wherever feasible.
That way, people using the printed output or online completion of
index entries don't see undifferentiated lists.  Consider this an
opportunity to make otherwise-identical index entries be more
specific, so readers can more easily find the exact place they are
looking for.

When you are making index entries, it is good practice to think of the
different ways people may look for something.  Different people
@emph{do not} think of the same words when they look something up.  A
helpful index will have items indexed under all the different words
that people may use.  For example, one reader may think it obvious
that the two-letter names for indices should be listed under
``Indices, two-letter names, since ``Indices'' are the general
concept.  But another reader may remember the specific concept of
two-letter names and search for the entry listed as ``Two letter names
for indices''.  A good index will have both entries and will help both
readers.

Like typesetting, the construction of an index is a skilled art, the
subtleties of which may not be appreciated until you need to do it
yourself.

@node Printing Indices & Menus
@section Printing Indices and Menus
@cindex Printing an index
@cindex Indices, printing and menus
@cindex Generating menus with indices
@cindex Menus generated with indices

To print an index means to include it as part of a manual or Info file.
This does not happen automatically just because you use @code{@@cindex}
or other index-entry generating commands in the Texinfo file; those just
cause the raw data for the index to be accumulated.  To generate an
index, you must include the @code{@@printindex} command at the place in
the document where you want the index to appear.  Also, as part of the
process of creating a printed manual, you must run a program called
@code{texindex} (@pxref{Hardcopy}) to sort the raw data to produce a
sorted index file.  The sorted index file is what is actually used to
print the index.

Texinfo offers six separate types of predefined index, which suffice
in most cases.  @xref{Indices}, for information on this, as well
defining your own new indices, combining indices, and, most
importantly advice on writing the actual index entries.  This section
focuses on printing indices, which is done with the
@code{@@printindex} command.

@findex printindex
@code{@@printindex} takes one argument, a two-letter index
abbreviation.  It reads the corresponding sorted index file (for
printed output), and formats it appropriately into an index.

The @code{@@printindex} command does not generate a chapter heading
for the index, since different manuals have different needs.
Consequently, you should precede the @code{@@printindex} command with
a suitable section or chapter command (usually @code{@@appendix} or
@code{@@unnumbered}) to supply the chapter heading and put the index
into the table of contents.  Precede the chapter heading with an
@code{@@node} line as usual.

For example:

@smallexample
@group
@@node Variable Index
@@unnumbered Variable Index

@@printindex vr
@end group

@group
@@node Concept Index
@@unnumbered Concept Index

@@printindex cp
@end group
@end smallexample

If you have more than one index, we recommend placing the concept index last.

@itemize
@item
In printed output, @code{@@printindex} produces a traditional
two-column index, with dot leaders between the index terms and page
numbers.

@item
In Info output, @code{@@printindex} produces a special menu containing
the line number of the entry, relative to the start of the node.  Info
readers can use this to go to the exact line of an entry, not just the
containing node.  (Older Info readers will just go to the node.)
Here's an example:

@smallexample
* First index entry:   Top.   (line  7)
@end smallexample

@noindent The actual number of spaces is variable, to right-justify
the line number; it's been reduced here to make the line fit in the
printed manual.

@item
In plain text output, @code{@@printindex} produces the same menu, but
the line numbers are relative to the start of the file, since that's
more convenient for that format.

@item
In HTML output, @code{@@printindex} produces links to the index
entries.

@item
In XML and Docbook output, it simply records the index to be printed.
@end itemize

@node Combining Indices
@section Combining Indices
@cindex Combining indices
@cindex Indices, combining them

Sometimes you will want to combine two disparate indices such as
functions and concepts, perhaps because you have few enough entries
that a separate index would look silly.

You could put functions into the concept index by writing
@code{@@cindex} commands for them instead of @code{@@findex} commands,
and produce a consistent manual by printing the concept index with the
title `Function and Concept Index' and not printing the `Function
Index' at all; but this is not a robust procedure.  It works only if
your document is never included as part of another document that is
designed to have a separate function index; if your document were to
be included with such a document, the functions from your document and
those from the other would not end up together.  Also, to make your
function names appear in the right font in the concept index, you
would need to enclose every one of them between the braces of
@code{@@code}.

@menu
* @code{@@syncodeindex}::               How to merge two indices, using @code{@@code}
                                 font for the merged-from index.
* @code{@@synindex}::                   How to merge two indices, using the
                                 roman font for the merged-from index.
@end menu

@node @code{@@syncodeindex}
@subsection @code{@@syncodeindex}: Combining indices using @code{@@code}

@anchor{syncodeindex}@c old name
@findex syncodeindex

When you want to combine functions and concepts into one index, you
should index the functions with @code{@@findex} and index the concepts
with @code{@@cindex}, and use the @code{@@syncodeindex} command to
redirect the function index entries into the concept index.

The @code{@@syncodeindex} command takes two arguments; they are the name
of the index to redirect, and the name of the index to redirect it to.
The template looks like this:

@example
@@syncodeindex @var{from} @var{to}
@end example

@cindex Predefined names for indices
@cindex Two letter names for indices
@cindex Indices, two letter names
@cindex Names for indices
For this purpose, the indices are given two-letter names:

@table @samp
@item cp
concept index
@item fn
function index
@item vr
variable index
@item ky
key index
@item pg
program index
@item tp
data type index
@end table

Write a @code{@@syncodeindex} command before or shortly after the
end-of-header line at the beginning of a Texinfo file.  For example,
to merge a function index with a concept index, write the
following:

@example
@@syncodeindex fn cp
@end example

@noindent
This will cause all entries designated for the function index to merge
in with the concept index instead.

To merge both a variables index and a function index into a concept
index, write the following:

@example
@group
@@syncodeindex vr cp
@@syncodeindex fn cp
@end group
@end example

@cindex Fonts for indices
The @code{@@syncodeindex} command puts all the entries from the `from'
index (the redirected index) into the @code{@@code} font, overriding
whatever default font is used by the index to which the entries are
now directed.  This way, if you direct function names from a function
index into a concept index, all the function names are printed in the
@code{@@code} font as you would expect.

@node @code{@@synindex}
@subsection @code{@@synindex}: Combining indices

@anchor{synindex}@c old name
@findex synindex

The @code{@@synindex} command is nearly the same as the
@code{@@syncodeindex} command, except that it does not put the `from'
index entries into the @code{@@code} font; rather it puts them in the
roman font.  Thus, you use @code{@@synindex} when you merge a concept
index into a function index.

@xref{Printing Indices & Menus}, for information about printing an index
at the end of a book or creating an index menu in an Info file.

@node New Indices
@section Defining New Indices

@cindex Defining new indices
@cindex Indices, defining new
@cindex New index defining
@findex defindex
@findex defcodeindex

In addition to the predefined indices (@pxref{Predefined Indices}),
you may use the @code{@@defindex} and @code{@@defcodeindex} commands
to define new indices.  These commands create new indexing @@-commands
with which you mark index entries.  The @code{@@defindex} command is
used like this:

@example
@@defindex @var{name}
@end example

New index names are usually two-letter words, such as @samp{au}.
For example:

@example
@@defindex au
@end example

This defines a new index, called the @samp{au} index.  At the same
time, it creates a new indexing command, @code{@@auindex}, that you
can use to make index entries.  Use this new indexing command just as
you would use a predefined indexing command.

For example, here is a section heading followed by a concept index
entry and two @samp{au} index entries.

@example
@@section Cognitive Semantics
@@cindex kinesthetic image schemas
@@auindex Johnson, Mark
@@auindex Lakoff, George
@end example

@noindent
(Evidently, @samp{au} serves here as an abbreviation for ``author''.)

Texinfo constructs the new indexing command by concatenating the name
of the index with @samp{index}; thus, defining an @samp{xy} index
leads to the automatic creation of an @code{@@xyindex} command.

Use the @code{@@printindex} command to print the index, as you do with
the predefined indices.  For example:

@example
@group
@@node Author Index
@@unnumbered Author Index

@@printindex au
@end group
@end example

The @code{@@defcodeindex} is like the @code{@@defindex} command,
except that, in the printed output, it prints entries in an
@code{@@code} font by default instead of a roman font.

You should define new indices before the end-of-header line of a
Texinfo file, and (of course) before any @code{@@synindex} or
@code{@@syncodeindex} commands (@pxref{Texinfo File Header}).

As mentioned earlier (@pxref{Predefined Indices}), we recommend having
a single index in the final document whenever possible, however many
source indices you use, since then readers have only one place to
look.

When creating an index, @TeX{} creates a file whose extension is the
name of the index (@pxref{Names of index files}).  Therefore you
should avoid using index names that collide with extensions used for
other purposes, such as @samp{.aux} or @samp{.xml}.
@command{makeinfo} already reports an error if a new index conflicts
well-known extension name.

@node Insertions
@chapter Special Insertions
@cindex Inserting special characters and symbols
@cindex Special insertions

Texinfo provides several commands for inserting characters that have
special meaning in Texinfo, such as braces, and for other graphic
elements that do not correspond to simple characters you can type.

@iftex
These are:

@itemize @bullet
@item The Texinfo special characters: @samp{@@ @{@} , \ #}.
@item Whitespace within and around a sentence.
@item Accents.
@item Dots and bullets.
@item The @TeX{} logo and the copyright symbol.
@item The euro and pounds currency symbols.
@item The degrees symbol.
@item The minus sign.
@item Mathematical expressions.
@item Glyphs for examples of programming: evaluation, macros, errors, etc.
@item Footnotes.
@end itemize
@end iftex

@menu
* Special Characters::          Inserting @@ @{@} , \ #
* Inserting Quote Characters::  Inserting left and right quotes, in code.
* Inserting Space::             Inserting the right amount of whitespace.
* Inserting Accents::           Inserting accents and special characters.
* Inserting Quotation Marks::   Inserting quotation marks.
* Inserting Subscripts and Superscripts:: Inserting sub/superscripts.
* Inserting Math::              Formatting mathematical expressions.
* Glyphs for Text::             Inserting dots, bullets, currencies, etc.
* Glyphs for Programming::      Indicating results of evaluation,
                                 expansion of macros, errors, etc.
* Inserting Unicode::           Inserting a Unicode character by code point.
@end menu

@node Special Characters
@section Special Characters: Inserting @@ @{@} , \ #
@anchor{Braces Atsign}@c previous names for this node
@anchor{Atsign Braces Comma}
@cindex Special characters, inserting
@cindex Commands to insert special characters

@samp{@@} and curly braces are the basic special characters in
Texinfo.  To insert these characters so they appear in text, you must
put an @samp{@@} in front of these characters to prevent Texinfo from
misinterpreting them.  Alphabetic commands are also provided.

The other characters (comma, backslash, hash) are special only in
restricted contexts, as explained in the respective sections.

@menu
* Inserting an Atsign::         @code{@@@@}, @code{@@atchar@{@}}.
* Inserting Braces::            @code{@@@{ @@@}}, @code{@@l rbracechar@{@}}.
* Inserting a Comma::           , and @code{@@comma@{@}}.
* Inserting a Backslash::       \ and @code{@@backslashchar@{@}}.
* Inserting a Hashsign::        # and @code{@@hashchar@{@}}.
@end menu

@node Inserting an Atsign
@subsection Inserting `@@' with @code{@@@@} and @code{@@atchar@{@}}
@cindex At sign, inserting
@cindex Inserting @@ @r{(literal @samp{@@})}
@findex @sortas{@@} @@ @r{(literal @samp{@@})}
@findex atchar@{@} @r{(literal @samp{@@})}

@code{@@@@} produces a single @samp{@@} character in the output.  Do
not put braces after an @code{@@@@} command.

@code{@@atchar@{@}} also produces a single @samp{@@} character in the
output.  It does need following braces, as usual for alphabetic
commands.  In inline conditionals (@pxref{Inline Conditionals}), it
can be necessary to avoid using the literal @samp{@@} character in the
source (and may be clearer in other contexts).

@node Inserting Braces
@subsection Inserting `@{ `@}' with @code{@@@{ @@@}} and @code{@@l rbracechar@{@}}

@findex @{ @r{(literal @samp{@{})}
@findex @} @r{(literal @samp{@}})}
@findex lbracechar@{@} @r{(literal @samp{@{})}
@findex rbracechar@{@} @r{(literal @samp{@}})}
@cindex Braces, inserting

@code{@@@{} produces a single @samp{@{} in the output, and @code{@@@}}
produces a single @samp{@}}.  Do not put braces after either an
@code{@@@{} or an @code{@@@}} command.

@code{@@lbracechar@{@}} and @code{@@rbracechar@{@}} also produce
single @samp{@{} and @samp{@}} characters in the output.  They do need
following braces, as usual for alphabetic commands.  In inline
conditionals (@pxref{Inline Conditionals}), it can be
necessary to avoid using literal brace characters in the source (and
may be clearer in other contexts).

@node Inserting a Comma
@subsection Inserting `,' with @code{@@comma@{@}}

@findex comma
@cindex Comma, inserting

Ordinarily, a comma `,' is a normal character that can be simply typed
in your input where you need it.

However, Texinfo uses the comma as a special character only in one
context: to separate arguments to those Texinfo commands, such as
@code{@@acronym} (@pxref{@code{@@acronym}}) and @code{@@xref}
(@pxref{Cross References}), as well as user-defined macros
(@pxref{Defining Macros}), which take more than one argument.

Since a comma character would confuse Texinfo's parsing for these
commands, you must use the command @samp{@@comma@{@}} instead if you want
to pass an actual comma.  Here are some examples:

@example
@@acronym@{ABC, A Bizarre @@comma@{@}@}
@@xref@{Comma,, The @@comma@{@} symbol@}
@@mymac@{One argument@@comma@{@} containing a comma@}
@end example

Although @samp{@@comma@{@}} can be used nearly anywhere, there is no
need for it anywhere except in this unusual case.

(Incidentally, the name @samp{@@comma} lacks the @samp{char} suffix used
in its companion commands only for historical reasons.  It didn't seem
important enough to define a synonym.)

@node Inserting a Backslash
@subsection Inserting `\' with @code{@@backslashchar@{@}}

@findex backslashchar
@cindex Backslash, inserting

Ordinarily, a backslash `\' is a normal character in Texinfo that can
be simply typed in your input where you need it.  The result is to
typeset the backslash from the typewriter font.

However, Texinfo uses the backslash as a special character in one
restricted context: to delimit formal arguments in the bodies of
user-defined macros (@pxref{Defining Macros}).

Due to the vagaries of macro argument parsing, it is more reliable to
pass an alphabetic command that produces a backslash instead of using
a literal \.  Hence @code{@@backslashchar@{@}}.  Here is an example
macro call:

@example
@@mymac@{One argument@@backslashchar@{@} with a backslash@}
@end example

@findex \backslash
Texinfo documents may also use \ as a command character inside
@code{@@math} (@pxref{Inserting Math}).  In this case, @code{@@\} or
@code{\backslash} produces a ``math'' backslash (from the math symbol
font), while @code{@@backslashchar@{@}} produces a typewriter
backslash as usual.

Although @samp{@@backslashchar@{@}} can be used nearly anywhere, there
is no need for it except in these unusual cases.

@node Inserting a Hashsign
@subsection Inserting `#' with @code{@@hashchar@{@}}

@findex hashchar@{@} @r{(literal @samp{#})}
@cindex Inserting #
@cindex Hash sign, inserting

Ordinarily, a hash `#' is a normal character in Texinfo that can be
simply typed in your input where you need it.  The result is to
typeset the hash character from the current font.

@cindex Number sign, inserting
@cindex Octotherp, inserting
@cindex Sharp sign (not), inserting
This character has many other names, varying by locale, such as
``number sign'', ``pound'', and ``octothorp''.  It is also sometimes
called ``sharp'' or ``sharp sign'' since it vaguely resembles the
musical symbol by that name.  In situations where Texinfo is used,
``hash'' is the most common in our experience.

However, Texinfo uses the hash character as a special character in one
restricted context: to introduce the so-called @code{#line} directive
and variants (@pxref{External Macro Processors}).

So, in order to typeset an actual hash character in such a place (for
example, in a program that needs documentation about @code{#line}),
it's necessary to use @code{@@hashchar@{@}} or some other construct.
Here's an example:

@example
@@hashchar@{@} 10 "example.c"
@end example

Although @samp{@@hashchar@{@}} can be used nearly anywhere, there
is no need for it anywhere except this unusual case.

@node Inserting Quote Characters
@section Inserting Quote Characters

@cindex Inserting quote characters
@cindex Quote characters, inserting

As explained in the early section on general Texinfo input conventions
(@pxref{Conventions}), Texinfo source files use the ASCII character
@code{`} (96 decimal) to produce a left quote (`), and ASCII @code{'}
(39 decimal) to produce a right quote (').  Doubling these input
characters (@code{``} and @code{''}) produces double quotes (`` and
'').  These are the conventions used by @TeX{}.

This works all right for text.  However, in examples of computer code,
readers are especially likely to cut and paste the text
verbatim---and, unfortunately, some document viewers will mangle these
characters.  (The free PDF reader @command{xpdf} works fine, but other
PDF readers, both free and nonfree, have problems.)

If this is a concern for you, Texinfo provides these two commands:

@table @code
@item @@codequoteundirected @var{on-off}
@findex codequoteundirected
@cindex undirected single quote
causes the output for the @code{'} character in code environments to
be the undirected single quote, like this:
@set txicodequoteundirected on
@code{'}.
@set txicodequoteundirected off

@item @@codequotebacktick @var{on-off}
@findex codequotebacktick
@cindex backtick
@cindex grave accent, standalone
causes the output for the @code{`} character in code environments to
be the backtick character (standalone grave accent), like this:
@set txicodequotebacktick on
@code{`}.
@set txicodequotebacktick off
@end table

If you want these settings for only part of the document,
@code{@@codequote... off} will restore the normal behavior, as in
@code{@@codequoteundirected off}.

These settings affect @code{@@code}, @code{@@example}, @code{@@kbd},
@code{@@samp}, @code{@@verb}, and @code{@@verbatim}.  @xref{Useful
Highlighting}.

@vindex txicodequoteundirected@r{, obsolete variable}
@vindex txicodequotebacktick@r{, obsolete variable}
This feature used to be controlled by using @code{@@set} to change the
values of the corresponding variables @code{txicodequoteundirected}
and @code{txicodequotebacktick}; they are still supported, but the
command interface is preferred.

@node Inserting Space
@section Inserting Space

@cindex Inserting space
@cindex Spacing, inserting
The following sections describe commands that control spacing of various
kinds within and after sentences.

@menu
* Multiple Spaces::             Inserting multiple spaces.
* Not Ending a Sentence::       Sometimes a . doesn't end a sentence.
* Ending a Sentence::           Sometimes it does.
* @code{@@frenchspacing}::              Specifying end-of-sentence spacing.
* @code{@@dmn}::                        Formatting a dimension.
@end menu

@node Multiple Spaces
@subsection Multiple Spaces

@cindex Multiple spaces
@cindex Whitespace, inserting
@cindex Space, inserting horizontal
@findex <space>
@findex <tab>
@findex <newline>

Ordinarily, multiple whitespace characters (space, tab, and newline)
are collapsed into a single space.

Occasionally, you may want to produce several consecutive spaces,
either for purposes of example (e.g., what your program does with
multiple spaces as input), or merely for purposes of appearance in
headings or lists.  Texinfo supports three commands:
@code{@@@kbd{SPACE}}, @code{@@@kbd{TAB}}, and @code{@@@kbd{NL}}, all
of which insert a single space into the output.  (Here,
@code{@@@kbd{SPACE}} represents an @samp{@@} character followed by a
space, i.e., @samp{@@ }, @kbd{TAB} represents an actual tab character,
and @code{@@@kbd{NL}} represents an @samp{@@} character and end-of-line,
i.e., when @samp{@@} is the last character on a line.)

For example,
@example
Spacey@@ @@ @@ @@
example.
@end example

@noindent produces

@example
Spacey@ @ @ @
example.
@end example

Other possible uses of @code{@@@kbd{SPACE}} have been subsumed by
@code{@@multitable} (@pxref{Multi-column Tables}).

Do not follow any of these commands with braces.

To produce a non-breakable space, see @ref{@code{@@tie}}.

@node Not Ending a Sentence
@subsection Not Ending a Sentence

@cindex Not ending a sentence
@cindex Sentence non-ending punctuation
@cindex Periods, inserting
@cindex Spacing, in the middle of sentences
When a period, exclamation point or question mark is
at the end of a sentence, slightly more space is
inserted after it in a typeset manual.

@findex <colon> @r{(suppress end-of-sentence space)}
@findex :
Usually, Texinfo can determine automatically when a period ends a
sentence.  However, special commands are needed in some circumstances.
Use the @code{@@:} command after a period, question mark, exclamation
mark or colon that should not be followed by extra space.  This is
necessary in the following situations:

@enumerate
@item After a period that ends a lowercase abbreviation which is not at
the end of a sentences.

@item When a parenthetical remark in the middle of a sentence (like
this one!)@: ends with a period, exclamation point or question mark,
@code{@@:} should be used after the right parenthesis.  Similarly for
right brackets and right quotes (both single and double).
@end enumerate

For example:

@example
@samp{foo vs.@@: bar (or?)@@: baz},
@end example

@noindent
The first line below shows the output, and for comparison, the second
line shows the spacing when the @samp{@@:} commands were not used.

@quotation
foo vs.@: bar (or?)@: baz@*
foo vs. bar (or?) baz
@end quotation

@iftex
If you look carefully, you will see a bit of extraneous space after the
@samp{vs.}@: and @samp{(or?)}@:.
@end iftex

It may help you to remember what @code{@@:} does by imagining that it
stands for an invisible lower-case character that stops a word ending in
a period.

A few Texinfo commands force normal interword spacing, so that you
don't have to insert @code{@@:} where you otherwise would.  These are
the code-like highlighting commands, @code{@@var}, @code{@@abbr}, and
@code{@@acronym} (@pxref{Useful Highlighting}).  For example, in
@samp{@@code@{foo. bar@}} the period is not considered to be the end of a
sentence, and no extra space is inserted.

@code{@@:} has no effect on the HTML or Docbook output.

@node Ending a Sentence
@subsection Ending a Sentence

@cindex Ending a Sentence
@cindex Sentence ending punctuation

@findex . @r{(end of sentence)}
@findex ! @r{(end of sentence)}
@findex ? @r{(end of sentence)}
@cindex Spacing, at ends of sentences
As mentioned above, Texinfo normally inserts additional space after
the end of a sentence.  It uses the same heuristic for this as @TeX{}:
a sentence ends with a period, exclamation point, or question mark,
either preceded or followed by optional closing punctuation, and then
whitespace, and @emph{not} preceded by a capital letter.

Use @code{@@.}@: instead of a period, @code{@@!}@: instead of an
exclamation point, and @code{@@?}@: instead of a question mark at the
end of a sentence that does end with a capital letter.  Do not put
braces after any of these commands.  For example:

@example
Give it to M.I.B. and to M.E.W@@.  Also, give it to R.J.C@@.
Give it to M.I.B. and to M.E.W.  Also, give it to R.J.C.
@end example

@noindent
The output follows.  In printed output and Info, you can see the
desired extra whitespace after the @samp{W} in the first line.

@quotation
Give it to M.I.B. and to M.E.W@.  Also, give it to R.J.C@.@*
Give it to M.I.B. and to M.E.W.  Also, give it to R.J.C.
@end quotation

In the HTML output, @code{@@.}@: is equivalent to a simple @samp{.};
likewise for @code{@@!}@: and @code{@@?}@:.

@cindex Closing punctuation, and sentence ending
The ``closing punctuation'' mentioned above is defined as a right
parenthesis (@samp{)}, right bracket (@samp{]}), or right quote,
either single or double (@samp{'} and @samp{''}; the many possible
additional Unicode right quotes are not included).  These characters
can be thought of as invisible with respect to whether a given period
ends a sentence.  (This is the same rule as @TeX{}.)  For instance,
the periods in @samp{foo.) Bar} and @samp{foo.'' Bar} do end
sentences.

The meanings of @code{@@:} and @code{@@.}, etc.@: in Texinfo are
designed to work well with the Emacs sentence motion commands
(@pxref{Sentences,,, emacs, The GNU Emacs Manual}).  It may help to
imagine that the @samp{@@} in @samp{@@.}, etc., is an invisible
lower-case letter `a' which makes an upper-case letter before it
immaterial for the purposes of deciding whether the period ends the
sentence.

A few Texinfo commands are not considered as being an abbreviation,
even though they may end with a capital letter when expanded, so that
you don't have to insert @code{@@.} and companions.  Notably, this is
the case for code-like highlighting commands, @code{@@var} arguments
ending with a capital letter, @code{@@LaTeX}, and @code{@@TeX}.  For
example, that sentence ended with @samp{... @@code@{@@@@TeX@}.};
@code{@@.} was not needed.  Similarly, in
@code{... @@var@{VARNAME@}. Text} the period after @var{VARNAME} ends
the sentence; there is no need to use @code{@@.}.

@node @code{@@frenchspacing}
@subsection @code{@@frenchspacing} @var{val}: Control Sentence Spacing

@anchor{frenchspacing}@c old name
@findex frenchspacing
@cindex French spacing
@cindex Sentences, spacing after
@cindex Space, after sentences

In American typography, it is traditional and correct to put extra
space at the end of a sentence.  This is the default in Texinfo
(implemented in Info and printed output; for HTML, we don't try to
override the browser).  In French typography (and others), this extra
space is wrong; all spaces are uniform.

Therefore Texinfo provides the @code{@@frenchspacing} command to
control the spacing after punctuation.  It reads the rest of the line
as its argument, which must be the single word @samp{on} or @samp{off}
(always these words, regardless of the language of the document).
Here is an example:

@example
@@frenchspacing on
This is text. Two sentences. Three sentences. French spacing.

@@frenchspacing off
This is text. Two sentences. Three sentences. Non-French spacing.
@end example

@noindent produces:

@frenchspacing on
This is text. Two sentences. Three sentences. French spacing.

@frenchspacing off
This is text. Two sentences. Three sentences. Non-French spacing.

@code{@@frenchspacing} also affects the output after @code{@@.},
@code{@@!}, and @code{@@?} (@pxref{Ending a Sentence}).

@code{@@frenchspacing} has no effect on the HTML or Docbook output;
for XML, it outputs a transliteration of itself (@pxref{Output
Formats}).

@node @code{@@dmn}
@subsection @code{@@dmn}@{@var{dimension}@}: Format a Dimension

@anchor{dmn}@c old name
@cindex Thin space between number, dimension
@cindex Dimension formatting
@cindex Format a dimension
@findex dmn

You can use the @code{@@dmn} command to format a dimension with a
little extra space in the printed output.  That is, on seeing
@code{@@dmn}, @TeX{} inserts just enough space for proper typesetting;
in other output formats, the formatting commands insert no space at
all.

To use the @code{@@dmn} command, write the number and then follow it
immediately, with no intervening space, by @code{@@dmn}, and then by
the dimension within braces.  For example,

@example
A4 paper is 8.27@@dmn@{in@} wide.
@end example

@noindent
produces

@quotation
A4 paper is 8.27@dmn{in} wide.
@end quotation

Not everyone uses this style.  Some people prefer `8.27@tie{}in.'@: or
`8.27@tie{}inches'.  In these cases, however, you need to use
@code{@@tie} (@pxref{@code{@@tie}}) or @code{@@w} (@pxref{@code{@@w}})
so that no line break can occur between the number and the dimension.
Also, if you write a period after an abbreviation within a sentence
(as with the `in.'@: above), you should write @samp{@@:} after the
period to prevent @TeX{} from inserting extra whitespace, as shown
here.  @xref{Not Ending a Sentence}.

@node Inserting Accents
@section Inserting Accents

@cindex Inserting accents
@cindex Accents, inserting
@cindex Floating accents, inserting

Here is a table with the commands Texinfo provides for inserting
floating accents.  They all need an argument, the character to accent,
which can either be given in braces as usual (@code{@@'@{e@}}), or, as
a special case, the braces can be omitted, in which case the argument
is the next character (@code{@@'e}).  This is to make the source as
convenient as possible to type and read, since accented characters are
very common in some languages.

If the command is alphabetic, such as @code{@@dotaccent}, then there
must be a space between the command name and argument if braces are
not used.  If the command is non-alphabetic, such as @code{@@'}, then
there must @emph{not} be a space; the argument is the very next
character.

Exception: the argument to @code{@@tieaccent} must be enclosed in
braces (since it is two characters instead of one).

To get the true accented characters output in Info, not just the ASCII
transliterations, it is necessary to specify @code{@@documentencoding}
with an encoding which supports the required characters
(@pxref{@code{@@documentencoding}}).  In this case, you can also use
non-ASCII (e.g., pre-accented) characters in the source file.

@findex " @r{(umlaut accent)}
@cindex Umlaut accent
@findex ' @r{(acute accent)}
@cindex Acute accent
@findex = @r{(macron accent)}
@cindex Macron accent
@findex ^ @r{(circumflex accent)}
@cindex Circumflex accent
@findex ` @r{(grave accent)}
@cindex Grave accent
@findex ~ @r{(tilde accent)}
@cindex Tilde accent
@findex , @r{(cedilla accent)}
@cindex Cedilla accent
@findex dotaccent
@cindex Dot accent
@findex H @r{(Hungarian umlaut accent)}
@cindex Hungarian umlaut accent
@findex ogonek
@cindex Ogonek diacritic
@findex ringaccent
@cindex Ring accent
@findex tieaccent
@cindex Tie-after accent
@findex u @r{(breve accent)}
@cindex Breve accent
@findex ubaraccent
@cindex Underbar accent
@findex udotaccent
@cindex Underdot accent
@findex v @r{(caron)}
@cindex Hacek accent
@cindex Check accent
@cindex Caron
@multitable {@t{@@questiondown@{@}}} {Output} {caron/hacek/check accent}
@headitem Command           @tab Output         @tab What
@item @t{@@"o}              @tab @"o            @tab umlaut accent
@item @t{@@'o}              @tab @'o            @tab acute accent
@item @t{@@,@{c@}}          @tab @,{c}          @tab cedilla accent
@item @t{@@=o}              @tab @=o            @tab macron/overbar accent
@item @t{@@^o}              @tab @^o            @tab circumflex accent
@item @t{@@`o}              @tab @`o            @tab grave accent
@item @t{@@~o}              @tab @~o            @tab tilde accent
@item @t{@@dotaccent@{o@}}  @tab @dotaccent{o}  @tab overdot accent
@item @t{@@H@{o@}}          @tab @H{o}          @tab long Hungarian umlaut
@item @t{@@ogonek@{a@}}     @tab @ogonek{a}     @tab ogonek
@item @t{@@ringaccent@{o@}} @tab @ringaccent{o} @tab ring accent
@item @t{@@tieaccent@{oo@}} @tab @tieaccent{oo} @tab tie-after accent
@item @t{@@u@{o@}}          @tab @u{o}          @tab breve accent
@item @t{@@ubaraccent@{o@}} @tab @ubaraccent{o} @tab underbar accent
@item @t{@@udotaccent@{o@}} @tab @udotaccent{o} @tab underdot accent
@item @t{@@v@{o@}}          @tab @v{o}          @tab caron/hacek/check accent
@end multitable

This table lists the Texinfo commands for inserting other characters
commonly used in languages other than English.

@findex questiondown
@cindex @questiondown{}
@findex exclamdown
@cindex @exclamdown{}
@findex aa
@cindex @aa{}
@findex AA
@cindex @AA{}
@findex ae
@cindex @ae{}
@findex AE
@cindex @AE{}
@cindex Icelandic
@cindex Eth
@findex dh
@cindex @dh{}
@findex DH
@cindex @DH{}
@findex dotless
@cindex @dotless{i} (dotless i)
@cindex @dotless{j} (dotless j)
@cindex Dotless i, j
@findex l
@cindex @l{}
@findex L
@cindex @L{}
@findex o
@cindex @o{}
@findex O
@cindex @O{}
@findex oe
@cindex @oe{}
@findex OE
@cindex @OE{}
@cindex Romance ordinals
@cindex Ordinals, Romance
@cindex Feminine ordinal
@findex ordf
@cindex @ordf{}
@cindex Masculine ordinal
@findex ordm
@cindex @ordm{}
@findex ss
@cindex @ss{}
@cindex Es-zet
@cindex Sharp S
@cindex German S
@cindex Thorn
@findex th
@cindex @th{}
@findex TH
@cindex @TH{}
@multitable {@t{@@questiondown@{@}}} {oe OE} {es-zet or sharp S}
@item @t{@@exclamdown@{@}}      @tab @exclamdown{}   @tab upside-down !
@item @t{@@questiondown@{@}}    @tab @questiondown{} @tab upside-down ?
@item @t{@@aa@{@} @@AA@{@}}     @tab @aa{} @AA{}     @tab a,A with circle
@item @t{@@ae@{@} @@AE@{@}}     @tab @ae{} @AE{}     @tab ae,AE ligatures
@item @t{@@dh@{@} @@DH@{@}}     @tab @dh{} @DH{}     @tab Icelandic eth
@item @t{@@dotless@{i@}}        @tab @dotless{i}     @tab dotless i
@item @t{@@dotless@{j@}}        @tab @dotless{j}     @tab dotless j
@item @t{@@l@{@} @@L@{@}}       @tab @l{} @L{}       @tab suppressed-L,l
@item @t{@@o@{@} @@O@{@}}       @tab @o{} @O{}       @tab O,o with slash
@item @t{@@oe@{@} @@OE@{@}}     @tab @oe{} @OE{}     @tab oe,OE ligatures
@item @t{@@ordf@{@} @@ordm@{@}} @tab @ordf{} @ordm{} @tab Spanish ordinals
@item @t{@@ss@{@}}              @tab @ss{}           @tab es-zet or sharp S
@item @t{@@th@{@} @@TH@{@}}     @tab @th{} @TH{}     @tab Icelandic thorn
@end multitable

@node Inserting Quotation Marks
@section Inserting Quotation Marks
@cindex Inserting quotation marks
@cindex Quotation marks, inserting

@cindex Quotation characters (`'), in source
Use doubled single-quote characters to begin and end quotations:
@w{@t{`@w{}`@dots{}'@w{}'}}.  @TeX{} converts two single quotes to
left- and right-hand doubled quotation marks,
@c this comes out as "like this" in Info, which is just confusing.
@iftex
``like this'',
@end iftex
and Info converts doubled single-quote characters to ASCII
double-quotes: @w{@t{`@w{}`@dots{}'@w{}'}} becomes @w{@t{"@dots{}"}}.

You may occasionally need to produce two consecutive single quotes;
for example, in documenting a computer language such as Maxima where
@t{'@w{}'} is a valid command.  You can do this with the input
@t{'@@w@{@}'}; the empty @code{@@w} command stops the combination into
the double-quote characters.

@cindex Unicode quotation characters
@cindex Grave accent, vs. left quote
The left quote character (@t{`}, ASCII code 96) used in Texinfo is a
grave accent in ANSI and ISO character set standards.  We use it as a
quote character because that is how @TeX{} is set up, by default.

Texinfo supports several other quotation marks used in languages other
than English.  Below is a table with the commands Texinfo provides for
inserting quotation marks.

@cindex UTF-8
@cindex ISO 8859-15
@cindex Latin 9
@cindex ISO 8859-1
@cindex Latin 1
In order to get the symbols for the quotation marks in encoded Info
output, it is necessary to specify @code{@@documentencoding UTF-8}.
(@xref{@code{@@documentencoding}}.)  Double guillemets are also
present in ISO 8859-1 (aka Latin@tie{}1) and ISO 8859-15 (aka
Latin@tie{}9).

@cindex European Computer Modern fonts
@cindex EC fonts
The standard @TeX{} fonts support the usual quotation marks used in
English (the ones produced with single and doubled ASCII
single-quotes).  For the other quotation marks, @TeX{} uses European
Computer Modern (EC) fonts (@file{ecrm1000} and other variants).
These fonts are freely available, of course; you can download them
from @url{http://ctan.org/pkg/ec}, among other places.

@cindex CM-Super fonts
The free EC fonts are bitmap fonts created with Metafont.  Especially
for on-line viewing, Type@tie{}1 (vector) versions of the fonts are
preferable; these are available in the CM-Super font package
(@url{http://ctan.org/pkg/cm-super}).

Both distributions include installation instructions.

@cindex Single quotation marks
@cindex Double quotation marks
@cindex Left quotation marks
@cindex Right quotation marks
@findex quotedblleft
@cindex `@w{}`
@findex quoteleft
@cindex `
@cindex " (undirected double quote character)
@findex quotedblright
@cindex '@w{}'
@findex quoteright
@cindex '
@cindex Double low-9 quotation mark
@cindex Single low-9 quotation mark
@findex quotedblbase
@cindex @quotedblbase{} (double low-9 quotation mark)
@findex quotesinglbase
@cindex @quotesinglbase{} (single low-9 quotation mark)
@cindex Angle quotation marks
@cindex Guillemets
@cindex Guillemots
@cindex French quotation marks
@cindex Quotation marks, French
@cindex German quotation marks
@cindex Quotation marks, German
@cindex Double guillemets
@cindex Single guillemets
@cindex Double angle quotation marks
@cindex Single angle quotation marks
@cindex Left-pointing angle quotation marks
@cindex Right-pointing angle quotation marks
@cindex Double left-pointing angle quotation mark
@cindex Double right-pointing angle quotation mark
@cindex Single left-pointing angle quotation mark
@cindex Single right-pointing angle quotation mark
@findex guillemetleft
@findex guillemotleft
@cindex @sortas{<<} @guillemetleft{}
@findex guillemetright
@findex guillemotright
@cindex @guillemetright{}
@findex guilsinglleft
@cindex @sortas{<} @guilsinglleft{}
@findex guilsinglright
@cindex @guilsinglright{}
@c The third column doesn't have the full text in the prototype so that
@c the Info output fits within 72 columns.
@multitable {@t{@@quotedblright@{@} '@w{}'}} {Glyph} {Right-pointing double angle quotation}
@headitem Command                    @tab Glyph             @tab Unicode name (point)
@item @verb{.@quotedblleft{} ``.}    @tab @quotedblleft{}   @tab Left double quotation mark (U+201C)
@item @verb{.@quotedblright{} ''.}   @tab @quotedblright{}  @tab Right double quotation mark (U+201D)
@item @verb{.@quoteleft{} `.}        @tab @quoteleft{}      @tab Left single quotation mark (U+2018)
@item @verb{.@quoteright{} '.}       @tab @quoteright{}     @tab Right single quotation mark (U+2019)
@item @t{@@quotedblbase@{@}}         @tab @quotedblbase{}   @tab Double low-9 quotation mark (U+201E)
@item @t{@@quotesinglbase@{@}}       @tab @quotesinglbase{} @tab Single low-9 quotation mark (U+201A)
@item @t{@@guillemetleft@{@}}        @tab @guillemetleft{}  @tab Left-pointing double angle quotation mark (U+00AB)
@item @t{@@guillemetright@{@}}       @tab @guillemetright{} @tab Right-pointing double angle quotation mark (U+00BB)
@item @t{@@guilsinglleft@{@}}        @tab @guilsinglleft{}  @tab Single left-pointing angle quotation mark (U+2039)
@item @t{@@guilsinglright@{@}}       @tab @guilsinglright{} @tab Single right-pointing angle quotation mark (U+203A)
@end multitable

@cindex Auk, bird species
For the double angle quotation marks, Adobe and @LaTeX{} glyph names
are also supported:  @code{@@guillemotleft} and
@code{@@guillemotright}.  These names are incorrect; a
``guillemot'' is a bird species (a type of auk).

Traditions for quotation mark usage vary to a great extent between
languages (@url{http://en.wikipedia.org/wiki/Quotation_mark}).
Texinfo does not provide commands or configurations for typesetting
quotation marks according to the numerous traditions.  Therefore, you
have to choose the commands appropriate for the language of your
manual.  Sometimes aliases (@pxref{@code{@@alias}}) can simplify the
usage and make the source code more readable.  For example, in German,
@code{@@quotedblbase} is used for the left double quote, and the right
double quote is the glyph produced by @code{@@quotedblleft}, which is
counter-intuitive.  Thus, in this case the following aliases would be
convenient:

@example
@@alias lgqq = quotedblbase
@@alias rgqq = quotedblleft
@end example

@node Inserting Subscripts and Superscripts
@section @code{@@sub} and @code{@@sup}: Inserting Subscripts and Superscripts

@findex sub
@findex sup
@cindex Subscripts and superscripts, text

You can insert subscripts and superscripts, in either text or math,
with the @code{@@sub} and @code{@@sup} commands.  (For other
mathematical expressions, see the next section.)  For example, here is
a purely textual subscript and superscript:

@example
here@@sub@{below@}@@sup@{above@}
@end example

@noindent produces:

@display
here@sub{below}@sup{above}
@end display

@cindex Math italic font
Inside @code{@@math}, @code{@@sub} and @code{@@sup} produce
mathematical subscripts and superscripts.  This uses a different font
in the @TeX{} output (math italic instead of text italic); it makes no
difference in the other output formats.  Here's an example:

@example
@@math@{e@@sup@{x@}@}
@end example

@noindent produces:

@display
@math{e@sup{x}}
@end display

In Info and plain text, regardless of being used inside @code{@@math},
@code{@@sub@{@var{text}@}} is output as @samp{_@{@var{text}@}} and
@code{@@sup@{@var{text}@}} as @samp{^@{@var{text}@}}, including the
literal braces (to mark the beginning and end of the ``script'' text
to the reader).

When the output format (and display program) permit (@TeX{} math,
HTML), the superscript is set above the subscript when both commands
are given consecutively.

@node Inserting Math
@section @code{@@math}: Inserting Mathematical Expressions

@anchor{math}@c old name
@findex math
@cindex Mathematical expressions, inserting
@cindex Formulas, mathematical

You can write a short mathematical expression with the @code{@@math}
command.  Write the mathematical expression between braces, like this:

@example
@@math@{(a + b) = (b + a)@}
@end example

@iftex
@noindent This produces the following in @TeX{}:

@display
@math{(a + b) = (b + a)}
@end display

@noindent and the following in other formats:
@end iftex
@ifnottex
@noindent This produces the following in Info and HTML:
@end ifnottex

@example
(a + b) = (b + a)
@end example

@cindex MathML, not used
The @code{@@math} command has no special effect on the Info and HTML
output.  @command{makeinfo} expands any @@-commands as usual, but it
does not try to use produce good mathematical formatting in any way
(no use of MathML, etc.).  The HTML output is enclosed by
@code{<em>...</em>}, but nothing more.

@findex \mathopsup
However, as far as the @TeX{} output is concerned, plain @TeX{}
mathematical commands are allowed in @code{@@math}, starting with
@samp{\}.  In essence, @code{@@math} switches into plain @TeX{} math
mode.  (Exception: the plain @TeX{} command @code{\sup}, which
typesets the mathematical operator name `sup', must be accessed as
@code{\mathopsup}, due to the conflict with Texinfo's @code{@@sup}
command.)

This allows you to use all the plain @TeX{} math control sequences for
symbols, functions, and so on, and thus get proper formatting in the
@TeX{} output, at least.

The @code{@@sub} and @code{@@sup} commands described in the previous
section produce subscripts and superscripts in HTML output as well as
@TeX{}; the plain @TeX{} characters @code{_} and @code{^} for
subscripts and superscripts are recognized by @TeX{} inside
@code{@@math}, but do nothing special in HTML or other output formats.

It's best to use @samp{\} instead of @samp{@@} for any such
mathematical commands; otherwise, @command{makeinfo} will complain.
On the other hand, @command{makeinfo} does allow input with matching
(but unescaped) braces, such as @samp{k_@{75@}}; it complains about
such bare braces in regular input.

Here's an example:

@example
@@math@{\sin 2\pi \equiv \cos 3\pi@}
@end example

@iftex
@noindent which looks like this in @TeX{}:
@display
@math{\sin 2\pi \equiv \cos 3\pi}
@end display

@noindent but
@end iftex
@noindent which looks like the input in Info and HTML:
@example
\sin 2\pi \equiv \cos 3\pi
@end example

@findex @sortas{\} \ @r{(literal \ in @code{@@math})}
Since @samp{\} is an escape character inside @code{@@math}, you can
use @code{@@\} to get a literal backslash (@code{\\} will work in
@TeX{}, but you'd get the literal two characters @samp{\\} in Info).
@code{@@\} is not defined outside of @code{@@math}, since a @samp{\}
ordinarily produces a literal (typewriter) @samp{\}.  You can also use
@code{@@backslashchar@{@}} in any mode to get a typewriter backslash.
@xref{Inserting a Backslash}.

@cindex Displayed equations
@cindex Equations, displayed
For displayed equations, you must at present use @TeX{} directly
(@pxref{Raw Formatter Commands}).

@node Glyphs for Text
@section Glyphs for Text

@anchor{Glyphs}@c old name
@anchor{TeX and copyright}@c another old node, now split into two
@cindex Glyphs for text
@cindex Textual glyphs

Texinfo has support for a few additional glyphs that are commonly used
in printed text but not available in ASCII@.  Of course, there are
many thousands more.  It is possible to use Unicode characters as-is
as far as @code{makeinfo} is concerned, but @TeX{} is not so lucky.

@menu
* @code{@@TeX @@LaTeX}::                 The @TeX{} logos.
* @code{@@copyright}::                  The copyright symbol (c in a circle).
* @code{@@registeredsymbol}::           The registered symbol (R in a circle).
* @code{@@dots}::                       How to insert ellipses: @dots{} and @enddots{}
* @code{@@bullet}::                     How to insert a bullet: @bullet{}
* @code{@@euro}::                       How to insert the euro currency symbol.
* @code{@@pounds}::                     How to insert the pounds currency symbol.
* @code{@@textdegree}::                 How to insert the degrees symbol.
* @code{@@minus}::                      How to insert a minus sign.
* @code{@@geq @@leq}::                   How to insert greater/less-than-or-equal signs.
@end menu

@node @code{@@TeX @@LaTeX}
@subsection @code{@@TeX}@{@} (@TeX{}) and @code{@@LaTeX}@{@} (@LaTeX{})

@anchor{tex}@c old name
@findex TeX
@findex LaTeX
@cindex Logos, @TeX{}
@cindex @TeX{} logo
@cindex @LaTeX{} logo

Use the @code{@@TeX@{@}} command to generate `@TeX{}'.  In a printed
manual, this is a special logo that is different from three ordinary
letters.  In Info, it just looks like @samp{TeX}.

Similarly, use the @code{@@LaTeX@{@}} command to generate `@LaTeX{}',
which is even more special in printed manuals (and different from the
incorrect @code{La@@TeX@{@}}.  In Info, the result is just
@samp{LaTeX}.  (@LaTeX{} is another macro package built on top of
@TeX{}, very loosely analogous to Texinfo in that it emphasizes
logical structure, but much (much) larger.)

The spelling of these commands are unusual for Texinfo, in that they
use both uppercase and lowercase letters.

@node @code{@@copyright}
@subsection @code{@@copyright@{@}} (@copyright{})

@anchor{copyright symbol}@c old name
@findex copyright
@cindex Copyright symbol

Use the @code{@@copyright@{@}} command to generate the copyright
symbol, `@copyright{}'.  Where possible, this is a @samp{c} inside a
circle; in Info, this is @samp{(C)}.

Legally, it's not necessary to use the copyright symbol; the English
word `Copyright' suffices, according to international treaty.

@node @code{@@registeredsymbol}
@subsection @code{@@registeredsymbol@{@}} (@registeredsymbol{})

@anchor{registered symbol}@c old name
@findex registeredsymbol
@cindex Registered symbol

Use the @code{@@registeredsymbol@{@}} command to generate the
registered symbol, `@registeredsymbol{}'.  Where possible, this is an
@samp{R} inside a circle; in Info, this is @samp{(R)}.

@node @code{@@dots}
@subsection @code{@@dots} (@dots{}) and @code{@@enddots} (@enddots{})

@anchor{dots}@c old name
@findex dots
@findex enddots
@cindex Inserting dots
@cindex Inserting ellipsis
@cindex Dots, inserting
@cindex Ellipsis, inserting

@anchor{Dots Bullets}@c old name

An @dfn{ellipsis} (a sequence of dots) would be spaced wrong when
typeset as a string of periods, so a special command is used in
Texinfo: use the @code{@@dots@{@}} command to generate a normal
ellipsis, which is three dots in a row, appropriately spaced @dots{}
like so.  To emphasize: do not simply write three periods in the input
file; that would work for the Info file output, but would produce the
wrong amount of space between the periods in the printed manual.

The @code{@@enddots@{@}} command generates an end-of-sentence
ellipsis, which also has three dots, but with different spacing
afterwards, @enddots{}  Look closely to see the difference.

Here is an ellipsis: @dots{}
Here are three periods in a row: ...

In printed (and usually HTML) output, the three periods in a row are
much closer together than the dots in the ellipsis.

@node @code{@@bullet}
@subsection @code{@@bullet} (@bullet{})

@anchor{bullet}@c old name
@findex bullet

Use the @code{@@bullet@{@}} command to generate a large round dot, or
the closest possible thing to one.  In Info, an asterisk is used.
Here is a bullet: @bullet{}

When you use @code{@@bullet} in @code{@@itemize}, you do not need to
type the braces, because @code{@@itemize} supplies them.
(@pxref{@code{@@itemize}}).

@node @code{@@euro}
@subsection @code{@@euro} (@euro{}): Euro Currency Symbol

@anchor{euro}@c old name
@findex euro
@cindex Euro symbol, producing

Use the @code{@@euro@{@}} command to generate `@euro{}'.  Where
possible, this is the symbol for the Euro currency.  Otherwise, the
word @samp{Euro} is used.

Texinfo cannot magically synthesize support for the Euro symbol where
the underlying system (fonts, software, whatever) does not support it.
Therefore, you may find it preferable to use the word ``Euro''.  (In
banking contexts, the abbreviation for the Euro is EUR@.)

@cindex ISO 8859-15, and Euro
@cindex Latin 9, and Euro
In order to get the Euro symbol in encoded Info output, for example,
it is necessary to specify @code{@@documentencoding ISO-8859-15} or
@code{@@documentencoding UTF-8} (@xref{@code{@@documentencoding}}.)
The Euro symbol is in ISO 8859-15 (aka Latin@tie{}9), and is
@emph{not} in the more widely-used ISO 8859-1 (Latin@tie{}1).

@pindex feymr10
@cindex Euro font
The Euro symbol does not exist in the standard @TeX{} fonts (which
were designed before the Euro was legislated into existence).
Therefore, @TeX{} uses an additional font, named @code{feymr10} (along
with other variables).  It is freely available, of course; you can
download it from @url{http://ctan.org/pkg/eurosym}, among other
places.  The distribution includes installation instructions.

@node @code{@@pounds}
@subsection @code{@@pounds} (@pounds{}): Pounds Sterling

@anchor{pounds}@c old name
@findex pounds
@cindex Pounds symbol

Use the @code{@@pounds@{@}} command to generate `@pounds{}'.  Where
possible, this is the symbol for the pounds sterling British currency.
Otherwise, it is @samp{#}.

@node @code{@@textdegree}
@subsection @code{@@textdegree} (@textdegree{}): Degrees Symbol

@anchor{textdegree}@c old name
@findex textdegree
@cindex Degree symbol

Use the @code{@@textdegree@{@}} command to generate `@textdegree{}'.
Where possible, this is the normal symbol for degrees.  Otherwise,
it is an @samp{o}.

@node @code{@@minus}
@subsection @code{@@minus} (@minus{}): Inserting a Minus Sign

@anchor{minus}@c old name
@findex minus
@cindex Minus sign

@cindex Em dash, compared to minus sign
@cindex Hyphen, compared to minus
Use the @code{@@minus@{@}} command to generate a minus sign.  In a
fixed-width font, this is a single hyphen, but in a proportional font,
the symbol is the customary length for a minus sign---a little longer
than a hyphen, shorter than an em-dash:

@display
@samp{@minus{}} is a minus sign generated with @samp{@@minus@{@}},

`-' is a hyphen generated with the character @samp{-},

`---' is an em-dash for text.
@end display

@noindent
In the fixed-width font used by Info, @code{@@minus@{@}} is the same
as a hyphen.

You should not use @code{@@minus@{@}} inside @code{@@code} or
@code{@@example} because the width distinction is not made in the
fixed-width font they use.

When you use @code{@@minus} to specify the mark beginning each entry
in an itemized list, you do not need to type the braces
(@pxref{@code{@@itemize}}).

If you actually want to typeset some math that does a subtraction, it
is better to use @code{@@math}.  Then the regular @samp{-} character
produces a minus sign, as in @code{@@math@{a-b@}} (@pxref{Inserting
Math}).

@node @code{@@geq @@leq}
@subsection @code{@@geq} (@geq{}) and @code{@@leq} (@leq{}): Inserting Relations

@anchor{geq leq}@c old name
@findex geq
@findex leq

Use the @code{@@geq@{@}} and @code{@@leq@{@}} commands to generate
greater-than-or-equal and less-than-equal-signs, `@geq{}' and
`@leq{}'.  When those symbols are not available, the ASCII sequences
@samp{>=} and @samp{<=} are output.

@node Glyphs for Programming
@section Glyphs for Programming

@cindex Glyphs for programming
@cindex Examples, glyphs for
@cindex Programming, glyphs for

In Texinfo, code is often illustrated in examples that are delimited
by @code{@@example} and @code{@@end example}, or by @code{@@lisp} and
@code{@@end lisp}.  In such examples, you can indicate the results of
evaluation or an expansion using @samp{@result{}} or
@samp{@expansion{}}.  Likewise, there are commands to insert glyphs to
indicate printed output, error messages, equivalence of expressions,
the location of point in an editor, and GUI operation sequences.

The glyph-insertion commands do not need to be used within an example,
but most often they are.  All glyph-insertion commands are followed by
empty braces.

@menu
* Glyphs Summary::
* @code{@@result}::                     How to show the result of expression.
* @code{@@expansion}::                  How to indicate an expansion.
* @code{@@print}::                      How to indicate generated output.
* @code{@@error}::                      How to indicate an error message.
* @code{@@equiv}::                      How to indicate equivalence.
* @code{@@point}::                      How to indicate the location of point.
* Click Sequences::             Inserting GUI usage sequences.
@end menu

@node Glyphs Summary
@subsection Glyphs Summary

Here is a summary of the glyph commands:

@table @asis
@item @result{}
@code{@@result@{@}} indicates the result of an expression.

@item @expansion{}
@code{@@expansion@{@}} indicates the results of a macro expansion.

@item @print{}
@code{@@print@{@}} indicates printed output.

@item @error{}
@code{@@error@{@}} indicates the following text is an error message.

@item @equiv{}
@code{@@equiv@{@}} indicates the exact equivalence of two forms.

@item @point{}
@code{@@point@{@}} shows the location of point.

@item @clicksequence{A @click{} B}
@code{@@clicksequence@{A @@click@{@} B} indicates a GUI operation
sequence: first A, then clicking B, or choosing B from a menu, or
otherwise selecting it.
@end table

@node @code{@@result}
@subsection @code{@@result@{@}} (@result{}): Result of an Expression

@anchor{result}@c old name
@findex result
@cindex Result of an expression
@cindex Indicating evaluation
@cindex Evaluation glyph
@cindex Value of an expression, indicating

Use the @code{@@result@{@}} command to indicate the result of
evaluating an expression.

The @code{@@result@{@}} command is displayed as @samp{@result{}},
either a double stemmed arrow or (when that is not available) the
ASCII sequence @samp{=>}.

Thus, the following,

@lisp
(cdr '(1 2 3))
    @result{} (2 3)
@end lisp

@noindent
may be read as ``@code{(cdr '(1 2 3))} evaluates to @code{(2 3)}''.

@node @code{@@expansion}
@subsection @code{@@expansion@{@}} (@expansion{}): Indicating an Expansion

@anchor{expansion}@c old name
@cindex Expansion, indicating
@cindex Macro expansion, indicating
@findex expansion

When an expression is a macro call, it expands into a new expression.
You can indicate the result of the expansion with the
@code{@@expansion@{@}} command.

The @code{@@expansion@{@}} command is displayed as
@samp{@expansion{}}, either a long arrow with a flat base or (when
that is not available) the ASCII sequence @samp{==>}.

@need 700
For example, the following

@example
@group
@@lisp
(third '(a b c))
    @@expansion@{@} (car (cdr (cdr '(a b c))))
    @@result@{@} c
@@end lisp
@end group
@end example

@noindent
produces

@lisp
@group
(third '(a b c))
    @expansion{} (car (cdr (cdr '(a b c))))
    @result{} c
@end group
@end lisp

@noindent
which may be read as:

@quotation
@code{(third '(a b c))} expands to @code{(car (cdr (cdr '(a b c))))};
the result of evaluating the expression is @code{c}.
@end quotation

@noindent
Often, as in this case, an example looks better if the
@code{@@expansion@{@}} and @code{@@result@{@}} commands are indented.

@node @code{@@print}
@subsection @code{@@print@{@}} (@print{}): Indicating Generated Output

@anchor{Print Glyph}@c old name
@findex print
@cindex Printed output, indicating

Sometimes an expression will generate output during its execution.
You can indicate such displayed output with the @code{@@print@{@}}
command.

The @code{@@print@{@}} command is displayed as @samp{@print{}}, either
a horizontal dash butting against a vertical bar or (when that is not
available) the ASCII sequence @samp{-|}.

In the following example, the printed text is indicated with
@samp{@print{}}, and the value of the expression follows on the
last line.

@lisp
@group
(progn (print 'foo) (print 'bar))
    @print{} foo
    @print{} bar
    @result{} bar
@end group
@end lisp

@noindent
In a Texinfo source file, this example is written as follows:

@lisp
@group
@@lisp
(progn (print 'foo) (print 'bar))
    @@print@{@} foo
    @@print@{@} bar
    @@result@{@} bar
@@end lisp
@end group
@end lisp

@node @code{@@error}
@subsection @code{@@error@{@}} (@error{}): Indicating an Error Message

@anchor{Error Glyph}@c old name
@cindex Error message, indicating
@findex error

A piece of code may cause an error when you evaluate it.  You can
designate the error message with the @code{@@error@{@}} command.

The @code{@@error@{@}} command is displayed as @samp{@error{}}, either
the word `error' in a box in the printed output, the word error
followed by an arrow in other formats or (when no arrow is available)
@samp{error-->}.

@need 700
Thus,

@example
@@lisp
(+ 23 'x)
@@error@{@} Wrong type argument: integer-or-marker-p, x
@@end lisp
@end example

@noindent
produces

@lisp
(+ 23 'x)
@error{} Wrong type argument: integer-or-marker-p, x
@end lisp

@noindent
This indicates that the following error message is printed
when you evaluate the expression:

@lisp
Wrong type argument: integer-or-marker-p, x
@end lisp

The word @samp{@error{}} itself is not part of the error message.

@node @code{@@equiv}
@subsection @code{@@equiv@{@}} (@equiv{}): Indicating Equivalence

@anchor{Equivalence}@c oldname
@cindex Equivalence, indicating
@findex equiv

Sometimes two expressions produce identical results.  You can indicate
the exact equivalence of two forms with the @code{@@equiv@{@}}
command.  The @code{@@equiv@{@}} command is displayed as
@samp{@equiv{}}, either a standard mathematical equivalence sign
(three parallel horizontal lines) or (when that is not available) as
the ASCII sequence @samp{==}.

Thus,

@example
@@lisp
(make-sparse-keymap) @@equiv@{@} (list 'keymap)
@@end lisp
@end example

@noindent
produces

@lisp
(make-sparse-keymap) @equiv{} (list 'keymap)
@end lisp

@noindent
This indicates that evaluating @code{(make-sparse-keymap)} produces
identical results to evaluating @code{(list 'keymap)}.

@node @code{@@point}
@subsection @code{@@point@{@}} (@point{}): Indicating Point in a Buffer

@anchor{Point Glyph}@c old name
@cindex Point, indicating in a buffer
@findex point

Sometimes you need to show an example of text in an Emacs buffer.  In
such examples, the convention is to include the entire contents of the
buffer in question between two lines of dashes containing the buffer
name.

You can use the @samp{@@point@{@}} command to show the location of
point in the text in the buffer.  (The symbol for point, of course, is
not part of the text in the buffer; it indicates the place
@emph{between} two characters where point is located.)

The @code{@@point@{@}} command is displayed as @samp{@point{}}, either
a pointed star or (when that is not available) the ASCII sequence
@samp{-!-}.

The following example shows the contents of buffer @file{foo} before
and after evaluating a Lisp command to insert the word @code{changed}.

@example
@group
---------- Buffer: foo ----------
This is the @point{}contents of foo.
---------- Buffer: foo ----------

@end group
@end example

@example
@group
(insert "changed ")
    @result{} nil
---------- Buffer: foo ----------
This is the changed @point{}contents of foo.
---------- Buffer: foo ----------

@end group
@end example

In a Texinfo source file, the example is written like this:

@example
@@example
---------- Buffer: foo ----------
This is the @@point@{@}contents of foo.
---------- Buffer: foo ----------

(insert "changed ")
    @@result@{@} nil
---------- Buffer: foo ----------
This is the changed @@point@{@}contents of foo.
---------- Buffer: foo ----------
@@end example
@end example

@node Click Sequences
@subsection Click Sequences

@cindex Click sequences
@cindex Sequence of clicks
@cindex GUI click sequence

@findex clicksequence
When documenting graphical interfaces, it is necessary to describe
sequences such as `Click on @samp{File}, then choose @samp{Open}, then
@dots{}'.  Texinfo offers commands @code{@@clicksequence} and
@code{click} to represent this, typically used like this:

@example
@dots{} @@clicksequence@{File @@click@{@} Open@} @dots{}
@end example

@noindent
which produces:

@display
@dots{} @clicksequence{File @click{} Open} @dots{}
@end display

@findex click
@findex arrow
The @code{@@click} command produces a right arrow by default; this
glyph is also available independently via the command
@code{@@arrow@{@}}.

@findex clickstyle
You can change the glyph produced by @code{@@click} with the command
@code{@@clickstyle}, which takes a command name as its single argument
on the rest of the line, much like @code{@@itemize} and friends
(@pxref{@code{@@itemize}}).  The command should produce a glyph, and
the usual empty braces @samp{@{@}} are omitted.  Here's an example:

@example
@@clickstyle @@result
@dots{} @@clicksequence@{File @@click@{@} Open@} @dots{}
@end example

@noindent
now produces:

@display
@clickstyle @result
@dots{} @clicksequence{File @click{} Open} @dots{}
@end display

@node Inserting Unicode
@section Inserting Unicode: @code{@@U}

@cindex Unicode character, inserting
@cindex Code point of Unicode character, inserting by
@findex U

The command @code{@@U@{@var{hex}@}} inserts a representation of the
Unicode character U+@var{hex}.  For example, @code{@@U@{0132@}}
inserts the Dutch `IJ' ligature (poorly shown here as simply the two
letters `I' and `J').

The @var{hex} value should be at least four hex digits; leading zeros
are @emph{not} added.  In general, @var{hex} must specify a valid
normal Unicode character; e.g., U+10FFFF (the very last code point) is
invalid by definition, and thus cannot be inserted this way.

@cindex ASCII, source document portability using
@code{@@U} is useful for inserting occasional glyphs for which Texinfo
has no dedicated command, while allowing the Texinfo source to remain
purely 7-bit ASCII for maximum portability.

@cindex Unicode and @TeX{}
This command has many limitations---the same limitations as inserting
Unicode characters in UTF-8 or another binary form.  First and most
importantly, @TeX{} knows nothing about most of Unicode.  Supporting
specific additional glyphs upon request is possible, but it's not
viable for @file{texinfo.tex} to support whole additional scripts
(Japanese, Urdu, @dots{}).  The @code{@@U} command does nothing to
change this.  If the specified character is not supported in @TeX{},
an error is given.  (@xref{@code{@@documentencoding}}.)

@cindex Entity reference in HTML et al.
@cindex @samp{&#x@var{hex};}, output from @code{@@U}
In HTML, XML, and Docbook, the output from @code{@@U} is always an
entity reference of the form @samp{&#x@var{hex};}, as in
@samp{Ĳ} for the example above.  This should work even when an
HTML document uses some other encoding (say, Latin@tie{}1) and the
given character is not supported in that encoding.

@cindex UTF-8, output from @code{@@U}
In Info and plain text, if the document encoding is specified
explicitly to be UTF-8, the output will be the UTF-8 representation of
the character U+@var{hex} (presuming it's a valid character).  In all
other cases, the output is the ASCII sequence @samp{U+@var{hex}}, as
in the six ASCII characters @samp{U+0132} for the example above.

That's all.  No magic!

@node Breaks
@chapter Forcing and Preventing Breaks

@cindex Forcing line and page breaks
@cindex Making line and page breaks
@cindex Preventing line and page breaks
@cindex Line breaks, awkward
@cindex Page breaks, awkward

Line and page breaks can sometimes occur in the `wrong' place in one
or another form of output.  It's up to you to ensure that text looks
right in all the output formats.

For example, in a printed manual, page breaks may occur awkwardly in
the middle of an example; to prevent this, you can hold text together
using a grouping command that keeps the text from being split across
two pages.  Conversely, you may want to force a page break where none
would occur normally.

You can use the break, break prevention, or pagination commands to fix
problematic line and page breaks.

@menu
* Break Commands::              Summary of break-related commands.
* Line Breaks::                 Forcing line breaks.
* @code{@@- @@hyphenation}::             Helping @TeX{} with hyphenation points.
* @code{@@allowcodebreaks}::            Controlling line breaks within @@code text.
* @code{@@w}::                          Preventing unwanted line breaks in text.
* @code{@@tie}::                        Inserting an unbreakable but varying space.
* @code{@@sp}::                         Inserting blank lines.
* @code{@@page}::                       Forcing the start of a new page.
* @code{@@group}::                      Preventing unwanted page breaks.
* @code{@@need}::                       Another way to prevent unwanted page breaks.
@end menu

@node Break Commands
@section Break Commands

The break commands create or allow line and paragraph breaks:

@table @code
@item @@*
Force a line break.

@item @@sp @var{n}
Skip @var{n} blank lines.

@item @@-
Insert a discretionary hyphen.

@item @@hyphenation@{@var{hy-phen-a-ted words}@}
Define hyphen points in @var{hy-phen-a-ted words}.
@end table

These commands hold text together on a single line:

@table @code
@item @@w@{@var{text}@}
Prevent @var{text} from being split and hyphenated across two lines.

@item @@tie@{@}
Insert a normal interword space at which a line break may not occur.
@end table

The pagination commands apply only to printed output, since other
output formats do not have pages.

@table @code
@item @@page
Start a new page.

@item @@group
Hold text together that must appear on one page.

@item @@need @var{mils}
Start a new page if not enough space on this one.
@end table

@node Line Breaks
@section @code{@@*} and @code{@@/}: Generate and Allow Line Breaks

@findex * @r{(force line break)}
@findex / @r{(allow line break)}
@cindex Line breaks, controlling
@cindex Controlling line breaks
@cindex Breaks in a line
@cindex Force line break
@cindex Allow line break

The @code{@@*} command forces a line break in all output formats.
The @code{@@/} command allows a line break (printed manual only).

Here is an example with @code{@@*}:

@example
This sentence is broken @@*into two lines.
@end example

@noindent produces

@example
@group
This sentence is broken
into two lines.
@end group
@end example

The @code{@@/} command can be useful within long urls or other
identifiers where @TeX{} can't find a good place to break.  @TeX{}
will automatically break urls at the natural places (@pxref{URL Line
Breaking}), so only use @code{@@/} if you need it.  @code{@@/} has no
effect in the other output format.

@node @code{@@- @@hyphenation}
@section @code{@@-} and @code{@@hyphenation}: Helping @TeX{} Hyphenate

@anchor{- and hyphenation}@c old name
@findex @sortas{-} - @r{(discretionary hyphen)}
@findex hyphenation
@cindex Hyphenation, helping @TeX{} do
@cindex Fine-tuning, and hyphenation

Although @TeX{}'s hyphenation algorithm is generally pretty good, it
does miss useful hyphenation points from time to time.  (Or, far more
rarely, insert an incorrect hyphenation.)  So, for documents with an
unusual vocabulary or when fine-tuning for a printed edition, you may
wish to help @TeX{} out.  Texinfo supports two commands for this:

@table @code
@item @@-
Insert a discretionary hyphen, i.e., a place where @TeX{} can (but does
not have to) hyphenate.  This is especially useful when you notice an
overfull hbox is due to @TeX{} missing a hyphenation (@pxref{Overfull
hboxes}).  @TeX{} will not insert any hyphenation points itself into a
word containing @code{@@-}.

@item @@hyphenation@{@var{hy-phen-a-ted words}@}
Tell @TeX{} how to hyphenate @var{hy-phen-a-ted words}.  As shown, you
put a @samp{-} at each hyphenation point.  For example:
@example
@@hyphenation@{man-u-script man-u-scripts@}
@end example
@noindent @TeX{} only uses the specified hyphenation points when the
words match exactly, so give all necessary variants, such as plurals.
@end table

Info, HTML, and other non-@TeX{} output is not hyphenated, so none of
these commands have any effect there.

@node @code{@@allowcodebreaks}
@section @code{@@allowcodebreaks}: Control Line Breaks in @code{@@code}

@anchor{allowcodebreaks}@c old name
@findex allowcodebreaks
@cindex Breaks, within @code{@@code}
@cindex @sortas{-} -, breakpoint within @code{@@code}
@cindex Hyphen, breakpoint within @code{@@code}
@cindex Dash, breakpoint within @code{@@code}
@cindex _, breakpoint within @code{@@code}
@cindex Underscore, breakpoint within @code{@@code}

Ordinarily, @TeX{} considers breaking lines at @samp{-} and @samp{_}
characters within @code{@@code} and related commands
(@pxref{@code{@@code}}), more or less as if they were ``empty''
hyphenation points.

This is necessary since many manuals, especially for Lisp-family
languages, must document very long identifiers.  On the other hand,
some manuals don't have this problems, and you may not wish to allow a
line break at the underscore in, for example, @code{SIZE_MAX}, or even
worse, after any of the four underscores in @code{__typeof__}.

So Texinfo provides this command:

@example
@@allowcodebreaks false
@end example

@noindent to prevent from breaking at @samp{-} or @samp{_} within
@code{@@code}.  You can go back to allowing such breaks with
@code{@@allowcodebreaks true}.  Write these commands on lines by
themselves.

These commands can be given anywhere in the document.  For example,
you may have just one problematic paragraph where you need to turn off
the breaks, but want them in general, or vice versa.

This command has no effect except in HTML and @TeX{} output.

@node @code{@@w}
@section @code{@@w}@{@var{text}@}: Prevent Line Breaks

@anchor{w}@c old name
@findex w
@cindex Line breaks, preventing

@code{@@w@{@var{text}@}} outputs @var{text}, while prohibiting line
breaks within @var{text}.

@cindex Non-breakable space, fixed
@cindex Unbreakable space, fixed
Thus, you can use @code{@@w} to produce a non-breakable space, fixed at
the width of a normal interword space:

@example
@@w@{ @} @@w@{ @} @@w@{ @} indentation.
@end example

@noindent produces:

@display
@w{ } @w{ } @w{ } indentation.
@end display

The space from @code{@@w@{@w{ }@}}, as well as being non-breakable,
also will not stretch or shrink.  Sometimes that is what you want, for
instance if you're doing manual indenting.  However, usually you want
a normal interword space that does stretch and shrink (in the printed
output); for that, see the @code{@@tie} command in the next section.

@cindex Hyphenation, preventing
You can also use the @code{@@w} command to prevent @TeX{} from
automatically hyphenating a long name or phrase that happens to fall
near the end of a line.  @command{makeinfo} does not ever hyphenate
words.

@cindex Keyword expansion, preventing
@cindex Version control keywords, preventing expansion of
@cindex $Id expansion, preventing
You can also use @code{@@w} to avoid unwanted keyword expansion in
source control systems.  For example, to literally write @t{@w{$}Id$}
in your document, use @code{@@w@{$@}Id$}.  This trick isn't effective
in Info or plain text output, though.

@node @code{@@tie}
@section @code{@@tie@{@}}: Inserting an Unbreakable Space

@anchor{tie}@c old name
@findex tie @r{(unbreakable interword space)}
@cindex Tied space
@cindex Non-breakable space, variable
@cindex Unbreakable space, variable

The @code{@@tie@{@}} command produces a normal interword space at which
a line break may not occur.  Always write it with following (empty)
braces, as usual for commands used within a paragraph.  Here's an
example:

@example
@@TeX@{@} was written by Donald E.@@tie@{@}Knuth.
@end example

@noindent produces:

@display
@TeX{} was written by Donald E.@tie{}Knuth.
@end display

There are two important differences between @code{@@tie@{@}} and
@code{@@w@{@w{ }@}}:

@itemize
@item
The space produced by @code{@@tie@{@}} will stretch and shrink slightly
along with the normal interword spaces in the paragraph; the space
produced by @code{@@w@{@w{ }@}} will not vary.

@item
@code{@@tie@{@}} allows hyphenation of the surrounding words, while
@code{@@w@{@w{ }@}} inhibits hyphenation of those words (for @TeX{}nical
reasons, namely that it produces an @samp{\hbox}).

@end itemize

@node @code{@@sp}
@section @code{@@sp} @var{n}: Insert Blank Lines

@anchor{sp}@c old name
@findex sp @r{(line spacing)}
@cindex Space, inserting vertical
@cindex Blank lines
@cindex Line spacing

A line beginning with and containing only @code{@@sp @var{n}}
generates @var{n} blank lines of space in both the printed manual and
the Info file.  @code{@@sp} also forces a paragraph break.  For
example,

@example
@@sp 2
@end example

@noindent
generates two blank lines.

The @code{@@sp} command is most often used in the title page.

@node @code{@@page}
@section @code{@@page}: Start a New Page

@anchor{page}@c old name
@findex page
@cindex Page breaks, forcing

A line containing only @code{@@page} starts a new page in a printed
manual.  In other formats, without the concept of pages, it starts a
new paragraph.  A @code{@@page} command is often used in the
@code{@@titlepage} section of a Texinfo file to start the copyright
page.

@node @code{@@group}
@section @code{@@group}: Prevent Page Breaks

@anchor{group}@c old name
@findex group
@cindex Group (hold text together vertically)
@cindex Holding text together vertically
@cindex Vertically holding text together

The @code{@@group} command (on a line by itself) is used inside an
@code{@@example} or similar construct to begin an unsplittable vertical
group, which will appear entirely on one page in the printed output.
The group is terminated by a line containing only @code{@@end group}.
These two lines produce no output of their own, and in the Info file
output they have no effect at all.

@c Once said that these environments
@c turn off vertical spacing between ``paragraphs''.
@c Also, quotation used to work, but doesn't in texinfo-2.72
Although @code{@@group} would make sense conceptually in a wide
variety of contexts, its current implementation works reliably only
within @code{@@example} and variants, and within @code{@@display},
@code{@@format}, @code{@@flushleft} and @code{@@flushright}.
@xref{Quotations and Examples}.  (What all these commands have in
common is that each line of input produces a line of output.)  In
other contexts, @code{@@group} can cause anomalous vertical
spacing.

@need 750
This formatting requirement means that you should write:

@example
@group
@@example
@@group
@dots{}
@@end group
@@end example
@end group
@end example

@noindent
with the @code{@@group} and @code{@@end group} commands inside the
@code{@@example} and @code{@@end example} commands.

The @code{@@group} command is most often used to hold an example
together on one page.  In this Texinfo manual, more than 100 examples
contain text that is enclosed between @code{@@group} and @code{@@end
group}.

If you forget to end a group, you may get strange and unfathomable
error messages when you run @TeX{}.  This is because @TeX{} keeps
trying to put the rest of the Texinfo file onto the one page and does
not start to generate error messages until it has processed
considerable text.  It is a good rule of thumb to look for a missing
@code{@@end group} if you get incomprehensible error messages in
@TeX{}.

@node @code{@@need}
@section @code{@@need @var{mils}}: Prevent Page Breaks

@anchor{need}@c old name
@findex need
@cindex Need space at page bottom
@cindex Mils, argument to @code{@@need}

A line containing only @code{@@need @var{n}} starts a new page in a
printed manual if fewer than @var{n} mils (thousandths of an inch)
remain on the current page.  Do not use braces around the argument
@var{n}.  The @code{@@need} command has no effect on other output
formats since they are not paginated.

@need 800
This paragraph is preceded by a @code{@@need} command that tells
@TeX{} to start a new page if fewer than 800 mils (eight-tenths
inch) remain on the page.  It looks like this:

@example
@group
@@need 800
This paragraph is preceded by @dots{}
@end group
@end example

@cindex Orphans, preventing
The @code{@@need} command is useful for preventing orphans: single
lines at the bottoms of printed pages.

@node Definition Commands
@chapter Definition Commands
@cindex Definition commands

The @code{@@deffn} command and the other @dfn{definition commands}
enable you to describe functions, variables, macros, commands, user
options, special forms and other such artifacts in a uniform
format.

In the Info file, a definition causes the entity
category---`Function', `Variable', or whatever---to appear at the
beginning of the first line of the definition, followed by the
entity's name and arguments.  In the printed manual, the command
causes @TeX{} to print the entity's name and its arguments on the left
margin and print the category next to the right margin.  In both
output formats, the body of the definition is indented.  Also, the
name of the entity is entered into the appropriate index:
@code{@@deffn} enters the name into the index of functions,
@code{@@defvr} enters it into the index of variables, and so
on (@pxref{Predefined Indices}).

A manual need not and should not contain more than one definition for
a given name.  An appendix containing a summary should use
@code{@@table} rather than the definition commands.

@menu
* Def Cmd Template::            Writing descriptions using definition commands.
* Def Cmd Continuation Lines::  Continuing the heading over source lines.
* Optional Arguments::          Handling optional and repeated arguments.
* @code{@@deffnx}::                     Group two or more `first' lines.
* Def Cmds in Detail::          Reference for all the definition commands.
* Def Cmd Conventions::         Conventions for writing definitions.
* Sample Function Definition::  An example.
@end menu

@node Def Cmd Template
@section The Template for a Definition
@cindex Definition template
@cindex Template for a definition

The @code{@@deffn} command is used for definitions of entities that
resemble functions.  To write a definition using the @code{@@deffn}
command, write the @code{@@deffn} command at the beginning of a line
and follow it on the same line by the category of the entity, the name
of the entity itself, and its arguments (if any).  Then write the body
of the definition on succeeding lines.  (You may embed examples in the
body.)  Finally, end the definition with an @code{@@end deffn} command
written on a line of its own.

The other definition commands follow the same format: a line with the
@code{@@def@dots{}} command and whatever arguments are appropriate for
that command; the body of the definition; and a corresponding
@code{@@end} line.

The template for a definition looks like this:

@example
@group
@@deffn @var{category} @var{name} @var{arguments}@dots{}
@var{body-of-definition}
@@end deffn
@end group
@end example

@need 700
@noindent
For example,

@example
@group
@@deffn Command forward-word count
This command moves point forward @@var@{count@} words
(or backward if @@var@{count@} is negative). @dots{}
@@end deffn
@end group
@end example

@noindent
produces

@quotation
@deffn Command forward-word count
This command moves point forward @var{count} words
(or backward if @var{count} is negative). @dots{}
@end deffn
@end quotation

Capitalize the category name like a title.  If the name of the
category contains spaces, as in the phrase `Interactive Command',
enclose it in braces.  For example:

@example
@group
@@deffn @{Interactive Command@} isearch-forward
@dots{}
@@end deffn
@end group
@end example

@noindent
Otherwise, the second word will be mistaken for the name of the
entity.  As a general rule, when any of the arguments in the heading
line @emph{except} the last one are more than one word, you need to
enclose them in braces.  This may also be necessary if the text
contains commands, for example, @samp{@{declaraci@@'on@}} if you are
writing in Spanish.

Some of the definition commands are more general than others.  The
@code{@@deffn} command, for example, is the general definition command
for functions and the like---for entities that may take arguments.
When you use this command, you specify the category to which the
entity belongs.  Three predefined, specialized variations
(@code{@@defun}, @code{@@defmac}, and @code{@@defspec}) specify the
category for you: ``Function'', ``Macro'', and ``Special Form''
respectively.  (In Lisp, a special form is an entity much like a
function.)  Similarly, the general @code{@@defvr} command is
accompanied by several specialized variations for describing
particular kinds of variables.

@xref{Sample Function Definition}, for a detailed example of a
function definition, including the use of @code{@@example} inside the
definition.

@node Def Cmd Continuation Lines
@section Definition Command Continuation Lines
@cindex Continuation lines in definition commands
@cindex Definition command headings, continuing
@cindex @sortas{@@} @samp{@@} as continuation in definition commands

The heading line of a definition command can get very long.
Therefore, Texinfo has a special syntax allowing them to be continued
over multiple lines of the source file: a lone @samp{@@} at the end of
each line to be continued.  Here's an example:

@example
@@defun fn-name @@
  arg1 arg2 arg3
This is the basic continued defun.
@@end defun
@end example

@noindent produces:

@defun fn-name   arg1 arg2 arg3
This is the basic continued defun.
@end defun

@noindent
As you can see, the continued lines are combined, as if they had been
typed on one source line.

Although this example only shows a one-line continuation,
continuations may extend over any number of lines, in the same way;
put an @code{@@} at the end of each line to be continued.

@cindex Whitespace, collapsed around continuations
@cindex Collapsing whitespace around continuations
In general, any number of spaces or tabs before the @code{@@}
continuation character are collapsed into a single space.  There is one
exception: the Texinfo processors will not fully collapse whitespace
around a continuation inside braces.  For example:

@example
@@deffn @{Category @@
  Name@} @dots{}
@end example

@noindent The output (not shown) has excess space between `Category'
and `Name'.  To avoid this, elide the unwanted whitespace in your
input, or put the continuation @code{@@} outside braces.

@code{@@} does not function as a continuation character in @emph{any}
other context.  Ordinarily, @samp{@@} followed by a whitespace
character (space, tab, newline) produces a normal interword space
(@pxref{Multiple Spaces}).

@node Optional Arguments
@section Optional and Repeated Arguments
@cindex Optional and repeated arguments
@cindex Repeated and optional arguments
@cindex Arguments, repeated and optional
@cindex Syntax, optional & repeated arguments
@cindex Meta-syntactic chars for arguments

@c This is consistent with the Emacs Lisp Reference Manual.
Some entities take optional or repeated arguments, conventionally
specified by using square brackets and ellipses: an argument enclosed
within square brackets is optional, and an argument followed by an
ellipsis is optional and may be repeated more than once.

Thus, [@var{optional-arg}] means that @var{optional-arg} is optional
and @var{repeated-args}@code{@dots{}} stands for zero or more
arguments.  Parentheses are used when several arguments are grouped
into additional levels of list structure in Lisp.

Here is the @code{@@defspec} line of an example of an imaginary
(complicated) special form:

@quotation
@defspec foobar (var [from to [inc]]) body@dots{}
@end defspec
@end quotation

@noindent
In this example, the arguments @var{from} and @var{to} are optional,
but must both be present or both absent.  If they are present,
@var{inc} may optionally be specified as well.  These arguments are
grouped with the argument @var{var} into a list, to distinguish them
from @var{body}, which includes all remaining elements of the
form.

In a Texinfo source file, this @code{@@defspec} line is written like
this:

@example
@@defspec foobar (var [from to [inc]]) body@@dots@{@}
@end example

@noindent
The function is listed in the Command and Variable Index under
@samp{foobar}.

@node @code{@@deffnx}
@section @code{@@deffnx}, et al.: Two or More `First' Lines

@anchor{deffnx}@c old node
@findex deffnx
@cindex Two `First' Lines for @code{@@deffn}
@cindex Grouping two definitions together
@cindex Definitions grouped together

To create two or more `first' or header lines for a definition, follow
the first @code{@@deffn} line by a line beginning with
@code{@@deffnx}.  The @code{@@deffnx} command works exactly like
@code{@@deffn} except that it does not generate extra vertical white
space between it and the preceding line.

@need 1000
For example,

@example
@group
@@deffn @{Interactive Command@} isearch-forward
@@deffnx @{Interactive Command@} isearch-backward
These two search commands are similar except @dots{}
@@end deffn
@end group
@end example

@noindent
produces

@deffn {Interactive Command} isearch-forward
@deffnx {Interactive Command} isearch-backward
These two search commands are similar except @dots{}
@end deffn

@findex defcvx
@findex defivarx
@findex defmacx
@findex defmethodx
@findex defoptx
@findex defopx
@findex defspecx
@findex deftpx
@findex deftypecvx
@findex deftypefnx
@findex deftypefunx
@findex deftypeivarx
@findex deftypemethodx
@findex deftypeopx
@findex deftypevarx
@findex deftypevrx
@findex defunx
@findex defvarx
@findex defvrx
Each definition command has an `x' form: @code{@@defunx},
@code{@@defvrx}, @code{@@deftypefunx}, etc.

The `x' forms work similarly to @code{@@itemx}
(@pxref{@code{@@itemx}}).

@node Def Cmds in Detail
@section The Definition Commands

Texinfo provides more than a dozen definition commands, all of which
are described in this section.

The definition commands automatically enter the name of the entity in
the appropriate index: for example, @code{@@deffn}, @code{@@defun},
and @code{@@defmac} enter function names in the index of functions;
@code{@@defvr} and @code{@@defvar} enter variable names in the index
of variables.

Although the examples that follow mostly illustrate Lisp, the commands
can be used for other programming languages.

@menu
* Functions Commands::          Commands for functions and similar entities.
* Variables Commands::          Commands for variables and similar entities.
* Typed Functions::             Commands for functions in typed languages.
* Typed Variables::             Commands for variables in typed languages.
* Data Types::                  The definition command for data types.
* Abstract Objects::            Commands for object-oriented programming.
@end menu

@node Functions Commands
@subsection Functions and Similar Entities

This section describes the commands for describing functions and similar
entities:

@table @code
@findex deffn
@item @@deffn @var{category} @var{name} @var{arguments}@dots{}
The @code{@@deffn} command is the general definition command for
functions, interactive commands, and similar entities that may take
arguments.  You must choose a term to describe the category of entity
being defined; for example, ``Function'' could be used if the entity is
a function.  The @code{@@deffn} command is written at the beginning of a
line and is followed on the same line by the category of entity being
described, the name of this particular entity, and its arguments, if
any.  Terminate the definition with @code{@@end deffn} on a line of its
own.

@need 750
For example, here is a definition:

@example
@group
@@deffn Command forward-char nchars
Move point forward @@var@{nchars@} characters.
@@end deffn
@end group
@end example

@noindent
This shows a rather terse definition for a ``command'' named
@code{forward-char} with one argument, @var{nchars}.

@code{@@deffn} prints argument names such as @var{nchars} in slanted
type in the printed output, because we think of these names as
metasyntactic variables---they stand for the actual argument values.
Within the text of the description, however, write an argument name
explicitly with @code{@@var} to refer to the value of the argument.
In the example above, we used @samp{@@var@{nchars@}} in this way.

In the extremely unusual case when an argument name contains
@samp{--}, or another character sequence which is treated specially
(@pxref{Conventions}), use @code{@@code} around the special
characters.  This avoids the conversion to typographic en-dashes and
em-dashes.
@c @var also works; that's what we used to recommend.

The template for @code{@@deffn} is:

@example
@group
@@deffn @var{category} @var{name} @var{arguments}@dots{}
@var{body-of-definition}
@@end deffn
@end group
@end example

@findex defun
@item @@defun @var{name} @var{arguments}@dots{}
The @code{@@defun} command is the definition command for functions.
@code{@@defun} is equivalent to @samp{@@deffn Function @dots{}}.
Terminate the definition with @code{@@end defun} on a line of its own.
Thus, the template is:

@example
@group
@@defun @var{function-name} @var{arguments}@dots{}
@var{body-of-definition}
@@end defun
@end group
@end example

@findex defmac
@item @@defmac @var{name} @var{arguments}@dots{}
The @code{@@defmac} command is the definition command for macros.
@code{@@defmac} is equivalent to @samp{@@deffn Macro @dots{}} and
works like @code{@@defun}.

@findex defspec
@item @@defspec @var{name} @var{arguments}@dots{}
The @code{@@defspec} command is the definition command for special
forms.  (In Lisp, a special form is an entity much like a function;
@pxref{Special Forms,,, elisp, GNU Emacs Lisp Reference Manual}.)
@code{@@defspec} is equivalent to @samp{@@deffn @{Special Form@}
@dots{}} and works like @code{@@defun}.
@end table

All these commands create entries in the index of functions.

@node Variables Commands
@subsection Variables and Similar Entities

Here are the commands for defining variables and similar
entities:

@table @code
@findex defvr
@item @@defvr @var{category} @var{name}
The @code{@@defvr} command is a general definition command for
something like a variable---an entity that records a value.  You must
choose a term to describe the category of entity being defined; for
example, ``Variable'' could be used if the entity is a variable.
Write the @code{@@defvr} command at the beginning of a line and
follow it on the same line by the category of the entity and the
name of the entity.

We recommend capitalizing the category name like a title.  If the name
of the category contains spaces, as in the name ``User Option'',
enclose it in braces.  Otherwise, the second word will be mistaken for
the name of the entity.  For example,

@example
@group
@@defvr @{User Option@} fill-column
This buffer-local variable specifies
the maximum width of filled lines.
@dots{}
@@end defvr
@end group
@end example

Terminate the definition with @code{@@end defvr} on a line of its
own.

The template is:

@example
@group
@@defvr @var{category} @var{name}
@var{body-of-definition}
@@end defvr
@end group
@end example

@code{@@defvr} creates an entry in the index of variables for @var{name}.

@findex defvar
@item @@defvar @var{name}
The @code{@@defvar} command is the definition command for variables.
@code{@@defvar} is equivalent to @samp{@@defvr Variable
@dots{}}.

@need 750
For example:

@example
@group
@@defvar kill-ring
@dots{}
@@end defvar
@end group
@end example

The template is:

@example
@group
@@defvar @var{name}
@var{body-of-definition}
@@end defvar
@end group
@end example

@code{@@defvar} creates an entry in the index of variables for
@var{name}.

@findex defopt
@item @@defopt @var{name}
@cindex User options, marking
The @code{@@defopt} command is the definition command for @dfn{user
options}, i.e., variables intended for users to change according to
taste; Emacs has many such (@pxref{Variables,,, emacs, The GNU Emacs
Manual}).  @code{@@defopt} is equivalent to @samp{@@defvr @{User
Option@} @dots{}} and works like @code{@@defvar}.  It creates an entry
in the index of variables.
@end table

@node Typed Functions
@subsection Functions in Typed Languages

@cindex Typed functions
@cindex Functions, in typed languages

The @code{@@deftypefn} command and its variations are for describing
functions in languages in which you must declare types of variables
and functions, such as C and C++.

@table @code
@findex deftypefn
@item @@deftypefn @var{category} @var{data-type} @var{name} @var{arguments}@dots{}
The @code{@@deftypefn} command is the general definition command for
functions and similar entities that may take arguments and that are
typed.  The @code{@@deftypefn} command is written at the beginning of
a line and is followed on the same line by the category of entity
being described, the type of the returned value, the name of this
particular entity, and its arguments, if any.

@need 800
@noindent
For example,

@example
@group
@@deftypefn @{Library Function@} int foobar @@
  (int @@var@{foo@}, float @@var@{bar@})
@dots{}
@@end deftypefn
@end group
@end example

produces:

@quotation
@deftypefn {Library Function} int foobar  (int @var{foo}, float @var{bar})
@dots{}
@end deftypefn
@end quotation

This means that @code{foobar} is a ``library function'' that returns an
@code{int}, and its arguments are @var{foo} (an @code{int}) and
@var{bar} (a @code{float}).

Since in typed languages, the actual names of the arguments are
typically scattered among data type names and keywords, Texinfo cannot
find them without help.  You can either (a)@tie{}write everything as
straight text, and it will be printed in slanted type; (b)@tie{}use
@code{@@var} for the variable names, which will uppercase the variable
names in Info and use the slanted typewriter font in printed output;
(c)@tie{}use @code{@@var} for the variable names and @code{@@code} for
the type names and keywords, which will be dutifully obeyed.

The template for @code{@@deftypefn} is:

@example
@group
@@deftypefn @var{category} @var{data-type} @var{name} @var{arguments} @dots{}
@var{body-of-description}
@@end deftypefn
@end group
@end example

@noindent
Note that if the @var{category} or @var{data type} is more than one
word then it must be enclosed in braces to make it a single argument.

If you are describing a procedure in a language that has packages,
such as Ada, you might consider using @code{@@deftypefn} in a manner
somewhat contrary to the convention described in the preceding
paragraphs.  For example:

@example
@group
@@deftypefn stacks private push @@
       (@@var@{s@}:in out stack; @@
       @@var@{n@}:in integer)
@dots{}
@@end deftypefn
@end group
@end example

@noindent
(In these examples the @code{@@deftypefn} arguments are shown using
continuations (@pxref{Def Cmd Continuation Lines}), but could be on a
single line.)

In this instance, the procedure is classified as belonging to the
package @code{stacks} rather than classified as a `procedure' and its
data type is described as @code{private}.  (The name of the procedure
is @code{push}, and its arguments are @var{s} and @var{n}.)

@code{@@deftypefn} creates an entry in the index of functions for
@var{name}.

@item @@deftypefun @var{data-type} @var{name} @var{arguments}@dots{}
@findex deftypefun
The @code{@@deftypefun} command is the specialized definition command
for functions in typed languages.  The command is equivalent to
@samp{@@deftypefn Function @dots{}}.  The template is:

@example
@group
@@deftypefun @var{type} @var{name} @var{arguments}@dots{}
@var{body-of-description}
@@end deftypefun
@end group
@end example

@code{@@deftypefun} creates an entry in the index of functions for
@var{name}.

@end table

@cindex Return type, own line for
@findex deftypefnnewline
Ordinarily, the return type is printed on the same line as the
function name and arguments, as shown above.  In source code, GNU
style is to put the return type on a line by itself.  So Texinfo
provides an option to do that: @code{@@deftypefnnewline on}.

This affects typed functions only---not untyped functions, not typed
variables, etc..  Specifically, it affects the commands in this
section, and the analogous commands for object-oriented languages,
namely @code{@@deftypeop} and @code{@@deftypemethod}
(@pxref{Object-Oriented Methods}).

Specifying @code{@@deftypefnnewline off} reverts to the default.

@node Typed Variables
@subsection Variables in Typed Languages

@cindex Typed variables
@cindex Variables, in typed languages

Variables in typed languages are handled in a manner similar to
functions in typed languages.  @xref{Typed Functions}.  The general
definition command @code{@@deftypevr} corresponds to
@code{@@deftypefn} and the specialized definition command
@code{@@deftypevar} corresponds to @code{@@deftypefun}.

@table @code
@findex deftypevr
@item @@deftypevr @var{category} @var{data-type} @var{name}
The @code{@@deftypevr} command is the general definition command for
something like a variable in a typed language---an entity that records
a value.  You must choose a term to describe the category of the
entity being defined; for example, ``Variable'' could be used if the
entity is a variable.

The @code{@@deftypevr} command is written at the beginning of a line
and is followed on the same line by the category of the entity
being described, the data type, and the name of this particular
entity.

@need 800
@noindent
For example:

@example
@group
@@deftypevr @{Global Flag@} int enable
@dots{}
@@end deftypevr
@end group
@end example

@noindent
produces the following:

@quotation
@deftypevr {Global Flag} int enable
@dots{}
@end deftypevr
@end quotation

@need 800
The template is:

@example
@@deftypevr @var{category} @var{data-type} @var{name}
@var{body-of-description}
@@end deftypevr
@end example

@findex deftypevar
@item @@deftypevar @var{data-type} @var{name}
The @code{@@deftypevar} command is the specialized definition command
for variables in typed languages.  @code{@@deftypevar} is equivalent
to @samp{@@deftypevr Variable @dots{}}.  The template is:

@example
@group
@@deftypevar @var{data-type} @var{name}
@var{body-of-description}
@@end deftypevar
@end group
@end example
@end table

These commands create entries in the index of variables.

@node Data Types
@subsection Data Types

Here is the command for data types:

@table @code
@findex deftp
@item @@deftp @var{category} @var{name} @var{attributes}@dots{}
The @code{@@deftp} command is the generic definition command for data
types.  The command is written at the beginning of a line and is
followed on the same line by the category, by the name of the type
(which is a word like @code{int} or @code{float}), and then by names of
attributes of objects of that type.  Thus, you could use this command
for describing @code{int} or @code{float}, in which case you could use
@code{data type} as the category.  (A data type is a category of
certain objects for purposes of deciding which operations can be
performed on them.)

In Lisp, for example,  @dfn{pair} names a particular data
type, and an object of that type has two slots called the
@sc{car} and the @sc{cdr}.  Here is how you would write the first line
of a definition of @code{pair}.

@example
@group
@@deftp @{Data type@} pair car cdr
@dots{}
@@end deftp
@end group
@end example

@need 950
The template is:

@example
@group
@@deftp @var{category} @var{name-of-type} @var{attributes}@dots{}
@var{body-of-definition}
@@end deftp
@end group
@end example

@code{@@deftp} creates an entry in the index of data types.
@end table

@node Abstract Objects
@subsection Object-Oriented Programming

@cindex Object-oriented programming

Here are the commands for formatting descriptions about abstract
objects, such as are used in object-oriented programming.  A class is
a defined type of abstract object.  An instance of a class is a
particular object that has the type of the class.  An instance
variable is a variable that belongs to the class but for which each
instance has its own value.

@menu
* Variables: Object-Oriented Variables.
* Methods:   Object-Oriented Methods.
@end menu

@node Object-Oriented Variables
@subsubsection Object-Oriented Variables

@cindex Variables, object-oriented

These commands allow you to define different sorts of variables in
object-oriented programming languages.

@table @code
@item @@defcv @var{category} @var{class} @var{name}
@findex defcv
The @code{@@defcv} command is the general definition command for
variables associated with classes in object-oriented programming.  The
@code{@@defcv} command is followed by three arguments: the category of
thing being defined, the class to which it belongs, and its
name.  For instance:

@example
@group
@@defcv @{Class Option@} Window border-pattern
@dots{}
@@end defcv
@end group
@end example

@noindent produces:
@defcv {Class Option} Window border-pattern
@dots{}
@end defcv

@code{@@defcv} creates an entry in the index of variables.

@item @@deftypecv @var{category} @var{class} @var{data-type} @var{name}
@findex deftypecv
The @code{@@deftypecv} command is the definition command for typed
class variables in object-oriented programming.  It is analogous to
@code{@@defcv} with the addition of the @var{data-type} parameter to
specify the type of the instance variable.  Ordinarily, the data type
is a programming language construct that should be marked with
@code{@@code}. For instance:

@example
@group
@@deftypecv @{Class Option@} Window @@code@{int@} border-pattern
@dots{}
@@end deftypecv
@end group
@end example

@noindent produces:

@deftypecv {Class Option} Window @code{int} border-pattern
@dots{}
@end deftypecv

@code{@@deftypecv} creates an entry in the index of variables.

@item @@defivar @var{class} @var{name}
@findex defivar
The @code{@@defivar} command is the definition command for instance
variables in object-oriented programming.  @code{@@defivar} is
equivalent to @samp{@@defcv @{Instance Variable@} @dots{}}.  For
instance:

@example
@group
@@defivar Window border-pattern
@dots{}
@@end defivar
@end group
@end example

@noindent produces:

@defivar Window border-pattern
@dots{}
@end defivar

@code{@@defivar} creates an entry in the index of variables.

@item @@deftypeivar @var{class} @var{data-type} @var{name}
@findex deftypeivar
The @code{@@deftypeivar} command is the definition command for typed
instance variables in object-oriented programming.  It is analogous to
@code{@@defivar} with the addition of the @var{data-type} parameter to
specify the type of the instance variable.  Ordinarily, the data type
is a programming language construct that should be marked with
@code{@@code}. For instance:

@example
@group
@@deftypeivar Window @@code@{int@} border-pattern
@dots{}
@@end deftypeivar
@end group
@end example

@noindent produces:

@deftypeivar Window @code{int} border-pattern
@dots{}
@end deftypeivar

@code{@@deftypeivar} creates an entry in the index of variables.

@end table

@node Object-Oriented Methods
@subsubsection Object-Oriented Methods

@cindex Methods, object-oriented

These commands allow you to define different sorts of function-like
entities resembling methods in object-oriented programming languages.
These entities take arguments, as functions do, but are associated with
particular classes of objects.

@table @code

@findex defop
@item @@defop @var{category} @var{class} @var{name} @var{arguments}@dots{}
The @code{@@defop} command is the general definition command for these
method-like entities.

For example, some systems have constructs called @dfn{wrappers} that
are associated with classes as methods are, but that act more like
macros than like functions.  You could use @code{@@defop Wrapper} to
describe one of these.

Sometimes it is useful to distinguish methods and @dfn{operations}.
You can think of an operation as the specification for a method.
Thus, a window system might specify that all window classes have a
method named @code{expose}; we would say that this window system
defines an @code{expose} operation on windows in general.  Typically,
the operation has a name and also specifies the pattern of arguments;
all methods that implement the operation must accept the same
arguments, since applications that use the operation do so without
knowing which method will implement it.

Often it makes more sense to document operations than methods.  For
example, window application developers need to know about the
@code{expose} operation, but need not be concerned with whether a
given class of windows has its own method to implement this operation.
To describe this operation, you would write:

@example
@@defop Operation windows expose
@end example

The @code{@@defop} command is written at the beginning of a line and
is followed on the same line by the overall name of the category of
operation, the name of the class of the operation, the name of the
operation, and its arguments, if any.

The template is:
@example
@group
@@defop @var{category} @var{class} @var{name} @var{arguments}@dots{}
@var{body-of-definition}
@@end defop
@end group
@end example

@code{@@defop} creates an entry, such as `@code{expose} on
@code{windows}', in the index of functions.

@findex deftypeop
@item @@deftypeop @var{category} @var{class} @var{data-type} @var{name} @var{arguments}@dots{}
The @code{@@deftypeop} command is the definition command for typed
operations in object-oriented programming.  It is similar to
@code{@@defop} with the addition of the @var{data-type} parameter to
specify the return type of the method.  @code{@@deftypeop} creates an
entry in the index of functions.

@item @@defmethod @var{class} @var{name} @var{arguments}@dots{}
@findex defmethod
The @code{@@defmethod} command is the definition command for methods
in object-oriented programming.  A method is a kind of function that
implements an operation for a particular class of objects and its
subclasses.
@ignore
@c ADR: Who cares?!?
@c KB: Oh, I don't know, I think this info is crucial!
In the Lisp Machine, methods actually were functions, but
they were usually defined with @code{defmethod}.
@end ignore

@code{@@defmethod} is equivalent to @samp{@@defop Method @dots{}}.
The command is written at the beginning of a line and is followed by
the name of the class of the method, the name of the method, and its
arguments, if any.

@noindent
For example:
@example
@group
@@defmethod @code{bar-class} bar-method argument
@dots{}
@@end defmethod
@end group
@end example

@noindent
illustrates the definition for a method called @code{bar-method} of
the class @code{bar-class}.  The method takes an argument.

@code{@@defmethod} creates an entry in the index of functions.

@item @@deftypemethod @var{class} @var{data-type} @var{name} @var{arguments}@dots{}
@findex deftypemethod
The @code{@@deftypemethod} command is the definition command for methods
in object-oriented typed languages, such as C++ and Java.  It is similar
to the @code{@@defmethod} command with the addition of the
@var{data-type} parameter to specify the return type of the method.
@code{@@deftypemethod} creates an entry in the index of functions.

@end table

The typed commands are affected by the @code{@@deftypefnnewline}
option (@pxref{Typed Functions,, Functions in Typed Languages}).

@node Def Cmd Conventions
@section Conventions for Writing Definitions
@cindex Definition conventions
@cindex Conventions for writing definitions

When you write a definition using @code{@@deffn}, @code{@@defun}, or
one of the other definition commands, please take care to use
arguments that indicate the meaning, as with the @var{count} argument
to the @code{forward-word} function.  Also, if the name of an argument
contains the name of a type, such as @var{integer}, take care that the
argument actually is of that type.

@node Sample Function Definition
@section A Sample Function Definition
@cindex Function definitions
@cindex Command definitions
@cindex Macro definitions, programming-language
@cindex Sample function definition

A function definition uses the @code{@@defun} and @code{@@end defun}
commands.  The name of the function follows immediately after the
@code{@@defun} command and it is followed, on the same line, by the
parameter list.

Here is a definition from @ref{Calling Functions,,, elisp, The GNU Emacs
Lisp Reference Manual}.

@quotation
@defun apply function &rest arguments
@code{apply} calls @var{function} with @var{arguments}, just
like @code{funcall} but with one difference: the last of
@var{arguments} is a list of arguments to give to
@var{function}, rather than a single argument.  We also say
that this list is @dfn{appended} to the other arguments.

@code{apply} returns the result of calling @var{function}.
As with @code{funcall}, @var{function} must either be a Lisp
function or a primitive function; special forms and macros
do not make sense in @code{apply}.

@example
(setq f 'list)
    @result{} list
(apply f 'x 'y 'z)
@error{} Wrong type argument: listp, z
(apply '+ 1 2 '(3 4))
    @result{} 10
(apply '+ '(1 2 3 4))
    @result{} 10

(apply 'append '((a b c) nil (x y z) nil))
    @result{} (a b c x y z)
@end example

An interesting example of using @code{apply} is found in the description
of @code{mapcar}.
@end defun
@end quotation

In the Texinfo source file, this example looks like this:

@example
@group
@@defun apply function &rest arguments
@@code@{apply@} calls @@var@{function@} with
@@var@{arguments@}, just like @@code@{funcall@} but with one
difference: the last of @@var@{arguments@} is a list of
arguments to give to @@var@{function@}, rather than a single
argument.  We also say that this list is @@dfn@{appended@}
to the other arguments.
@end group

@group
@@code@{apply@} returns the result of calling
@@var@{function@}.  As with @@code@{funcall@},
@@var@{function@} must either be a Lisp function or a
primitive function; special forms and macros do not make
sense in @@code@{apply@}.
@end group

@group
@@example
(setq f 'list)
    @@result@{@} list
(apply f 'x 'y 'z)
@@error@{@} Wrong type argument: listp, z
(apply '+ 1 2 '(3 4))
    @@result@{@} 10
(apply '+ '(1 2 3 4))
    @@result@{@} 10

(apply 'append '((a b c) nil (x y z) nil))
    @@result@{@} (a b c x y z)
@@end example
@end group

@group
An interesting example of using @@code@{apply@} is found
in the description of @@code@{mapcar@}.
@@end defun
@end group
@end example

@noindent
In this manual, this function is listed in the Command and Variable
Index under @code{apply}.

Ordinary variables and user options are described using a format like
that for functions except that variables do not take arguments.

@node Internationalization
@chapter Internationalization

@cindex Internationalization
Texinfo has some support for writing in languages other than English,
although this area still needs considerable work.  (If you are
the one helping to translate the fixed strings written to documents,
@pxref{Internationalization of Document Strings}.)

For a list of the various accented and special characters Texinfo
supports, see @ref{Inserting Accents}.

@menu
* @code{@@documentlanguage}::           Declaring the current language.
* @code{@@documentencoding}::           Declaring the input encoding.
@end menu

@node @code{@@documentlanguage}
@section @code{@@documentlanguage @var{ll}[_@var{cc}]}: Set the Document Language
@anchor{documentlanguage}

@findex documentlanguage
@cindex Language, declaring
@cindex Locale, declaring
@cindex Document language, declaring

The @code{@@documentlanguage} command declares the current document
locale.  Write it on a line by itself, near the beginning of the file.

@example
@@documentlanguage @var{ll}[_@var{cc}]
@end example

Include a two-letter ISO@tie{}639-2 language code (@var{ll}) following
the command name, optionally followed by an underscore and two-letter
ISO@tie{}3166 two-letter country code (@var{cc}).  If you have a
multilingual document, the intent is to be able to use this command
multiple times, to declare each language change.  If the command is
not used at all, the default is @code{en_US} for US English.

As with GNU Gettext (@pxref{Top,,, gettext, Gettext}), if the country
code is omitted, the main dialect is assumed where possible.  For
example, @code{de} is equivalent to @code{de_DE} (German as spoken in
Germany).

@cindex Document strings, translation of
For Info and other online output, this command changes the translation
of various @dfn{document strings} such as ``see'' in cross-references
(@pxref{Cross References}), ``Function'' in defuns (@pxref{Definition
Commands}), and so on.  Some strings, such as ``Node:'', ``Next:'',
``Menu:'', etc., are keywords in Info output, so are not translated
there; they are translated in other output formats.

@cindex @file{txi-@var{cc}.tex}
For @TeX{}, this command causes a file @file{txi-@var{locale}.tex} to
be read (if it exists).  If @code{@@documentlanguage} argument
contains the optional @samp{_@var{cc}} suffix, this is tried first.
For example, with @code{@@documentlanguage de_DE}, @TeX{} first looks
for @file{txi-de_DE.tex}, then @file{txi-de.tex}.

Such a @file{txi-*} file is intended to redefine the various English
words used in @TeX{} output, such as `Chapter', `See', and so on.  We
are aware that individual words like these cannot always be translated
in isolation, and that a very different strategy would be required for
ideographic (among other) scripts.  Help in improving Texinfo's
language support is welcome.

@cindex Hyphenation patterns, language-dependent
@code{@@documentlanguage} also changes @TeX{}'s current hyphenation
patterns, if the @TeX{} program being run has the necessary support
included.  This will generally not be the case for @command{tex}
itself, but will usually be the case for up-to-date distributions of
the extended @TeX{} programs @command{etex} (DVI output) and
@command{pdftex} (PDF output).  @command{texi2dvi} will use the
extended @TeX{}s if they are available (@pxref{Format with
@command{texi2dvi}}).

In September 2006, the W3C Internationalization Activity released a
new recommendation for specifying languages:
@url{http://www.rfc-editor.org/rfc/bcp/bcp47.txt}.  When Gettext
supports this new scheme, Texinfo will too.

@cindex ISO 639-2 language codes
@cindex ISO 3166 country codes
@cindex Language codes
@cindex Country codes
Since the lists of language codes and country codes are updated
relatively frequently, we don't attempt to list them here.  The valid
language codes are on the official home page for ISO@tie{}639,
@url{http://www.loc.gov/standards/iso639-2/}.  The country codes and
the official web site for ISO@tie{}3166 can be found via
@url{http://en.wikipedia.org/wiki/ISO_3166}.

@node @code{@@documentencoding}
@section @code{@@documentencoding @var{enc}}: Set Input Encoding

@anchor{documentencoding}@c old name
@findex documentencoding
@cindex Encoding, declaring
@cindex Input encoding, declaring
@cindex Character set, declaring
@cindex Document input encoding

The @code{@@documentencoding} command declares the input document
encoding, and can also affect the encoding of the output.  Write it on
a line by itself, with a valid encoding specification following, near
the beginning of the file.

@example
@@documentencoding @var{enc}
@end example

Texinfo supports these encodings:

@table @code
@item US-ASCII
This has no particular effect, but it's included for completeness.

@item UTF-8
The vast global character encoding, expressed in 8-bit bytes.

@item ISO-8859-1
@itemx ISO-8859-15
@itemx ISO-8859-2
@cindex Euro symbol, and encodings
These specify the standard encodings for Western European (the first
two) and Eastern European languages (the third), respectively.  ISO
8859-15 replaces some little-used characters from 8859-1 (e.g.,
precomposed fractions) with more commonly needed ones, such as the
Euro symbol (@euro{}).

A full description of the encodings is beyond our scope here;
one useful reference is @uref{http://czyborra.com/charsets/iso8859.html}.

@item koi8-r
This is the commonly used encoding for the Russian language.

@item koi8-u
This is the commonly used encoding for the Ukrainian language.

@end table

Specifying an encoding @var{enc} has the following effects:

@cindex Local Variables section, for encoding
@cindex Info output, and encoding
In Info output, a so-called `Local Variables' section (@pxref{File
Variables,,, emacs, The GNU Emacs Manual}) is output including
@var{enc}.  This allows Info readers to set the encoding
appropriately.  It looks like this:

@example
Local Variables:
coding: @var{enc}
End:
@end example

Also, in Info and plain text output, unless the option
@option{--disable-encoding} is given to @command{makeinfo}, accent
constructs and special characters, such as @code{@@'e}, are output as
the actual 8-bit or UTF-8 character in the given encoding where
possible.

@cindex HTML output, and encodings
@cindex @code{http-equiv}, and charset specification
@cindex @code{<meta>} HTML tag, and charset specification
In HTML output, a @samp{<meta>} tag is output, in the @samp{<head>}
section of the HTML, that specifies @var{enc}.  Web servers and
browsers cooperate to use this information so the correct encoding is
used to display the page, if supported by the system.  That looks like
this:

@example
<meta http-equiv="Content-Type" content="text/html;
     charset=@var{enc}">
@end example

In XML and Docbook output, UTF-8 is always used for the output,
according to the conventions of those formats.

@cindex Computer Modern fonts
In @TeX{} output, the characters which are supported in the standard
Computer Modern fonts are output accordingly.  For example, this
means using constructed accents rather than precomposed glyphs.
Using a missing character generates a warning message, as does
specifying an unimplemented encoding.

Although modern @TeX{} systems support nearly every script in use in
the world, this wide-ranging support is not available in
@file{texinfo.tex}, and it's not feasible to duplicate or incorporate
all that effort.  (Our plan to support other scripts is to create a
@LaTeX{} back-end to @command{texi2any}, where the support is already
present.)

For maximum portability of Texinfo documents across the many different
user environments in the world, we recommend sticking to 7-bit ASCII
in the input unless your particular manual needs a substantial amount
of non-ASCII, e.g., it's written in German.  You can use the
@code{@@U} command to insert an occasional needed character
(@pxref{Inserting Unicode}).

@node Conditionals
@chapter Conditionally Visible Text
@cindex Conditionally visible text
@cindex Text, conditionally visible
@cindex Visibility of conditional text
@cindex If text conditionally visible

The @dfn{conditional commands} allow you to use different text for
different output formats, or for general conditions that you define.
For example, you can use them to specify different text for the
printed manual and the Info output.

The conditional commands comprise the following categories.

@itemize @bullet
@item
Commands specific to an output format (Info, @TeX{}, HTML, @dots{}).

@item
Commands specific to any output format @emph{excluding} a given
one (e.g., not Info, not @TeX{}, @dots{}).

@item
`Raw' formatter text for any output format, passed straight
through with minimal (but not zero) interpretation of @@-commands.

@item
Format-independent variable substitutions, and testing if a variable
is set or clear.

@end itemize

@menu
* Conditional Commands::        Text for a given format.
* Conditional Not Commands::    Text for any format other than a given one.
* Raw Formatter Commands::      Using raw formatter commands.
* Inline Conditionals::         Brace-delimited conditional text.
* @code{@@set @@clear @@value}::          Variable tests and substitutions.
* Testing for Texinfo Commands:: Testing if a Texinfo command is available.
* Conditional Nesting::         Using conditionals inside conditionals.
@end menu

@node Conditional Commands
@section Conditional Commands

Texinfo has an @code{@@if@var{format}} environment for each output
format, to allow conditional inclusion of text for a particular output
format.

@findex ifinfo
@code{@@ifinfo} begins segments of text that should be ignored by
@TeX{} when it typesets the printed manual, and by @command{makeinfo}
when not producing Info output.  The segment of text appears only in
the Info file and, for historical compatibility, the plain text
output.

@findex ifdocbook
@findex ifhtml
@findex ifplaintext
@findex iftex
@findex ifxml
The environments for the other formats are analogous:

@table @code
@item @@ifdocbook @dots{} @@end ifdocbook
Text to appear only in the Docbook output.

@item @@ifhtml @dots{} @@end ifhtml
Text to appear only in the HTML output.

@item @@ifplaintext @dots{} @@end ifplaintext
Text to appear only in the plain text output.

@item @@iftex @dots{} @@end iftex
Text to appear only in the printed manual.

@item @@ifxml @dots{} @@end ifxml
Text to appear only in the XML output.
@end table

The @code{@@if@dots{}} and @code{@@end if@dots{}} commands must appear
on lines by themselves in your source file.  The newlines following
the commands are (more or less) treated as whitespace, so that the
conditional text is flowed normally into a surrounding paragraph.

The @code{@@if@dots{}} constructs are intended to conditionalize
normal Texinfo source; @pxref{Raw Formatter Commands}, for using
underlying format commands directly.

Here is an example showing all these conditionals:

@example
@@iftex
This text will appear only in the printed manual.
@@end iftex
@@ifinfo
However, this text will appear only in Info and plain text.
@@end ifinfo
@@ifhtml
And this text will only appear in HTML.
@@end ifhtml
@@ifplaintext
Whereas this text will only appear in plain text.
@@end ifplaintext
@@ifxml
Notwithstanding that this will only appear in XML@.
@@end ifxml
@@ifdocbook
Nevertheless, this will only appear in Docbook.
@@end ifdocbook
@end example

@noindent
The preceding example produces the following line:

@iftex
This text will appear only in the printed manual.
@end iftex
@ifinfo
However, this text will appear only in Info and plain text.
@end ifinfo
@ifhtml
And this text will only appear in HTML.
@end ifhtml
@ifplaintext
Whereas this text will only appear in plain text.
@end ifplaintext
@ifxml
Notwithstanding that this will only appear in XML@.
@end ifxml
@ifdocbook
Nevertheless, this will only appear in Docbook.
@end ifdocbook

@noindent
Notice that you only see one of the input lines, depending on which
version of the manual you are reading.

@findex errormsg
In complex documents, you may want Texinfo to issue an error message
in some conditionals that should not ever be processed.  The
@code{@@errormsg@{@var{text}@}} command will do this; it takes one
argument, the text of the error message.

We mention @code{@@errormsg@{@}} here even though it is not strictly
related to conditionals, since in practice it is most likely to be
useful in that context.  Technically, it can be used anywhere.
@xref{External Macro Processors}, for a caveat regarding the line
numbers which @code{@@errormsg} emits in @TeX{}.

@node Conditional Not Commands
@section Conditional Not Commands
@findex ifnotdocbook
@findex ifnothtml
@findex ifnotinfo
@findex ifnotplaintext
@findex ifnottex
@findex ifnotxml

You can specify text to be included in any output format @emph{other}
than a given one with the @code{@@ifnot@dots{}} environments:

@example
@@ifnotdocbook @dots{} @@end ifnotdocbook
@@ifnothtml @dots{} @@end ifnothtml
@@ifnotinfo @dots{} @@end ifnotinfo
@@ifnotplaintext @dots{} @@end ifnotplaintext
@@ifnottex @dots{} @@end ifnottex
@@ifnotxml @dots{} @@end ifnotxml
@end example

@noindent
The @code{@@ifnot@dots{}} command and the @code{@@end} command must
appear on lines by themselves in your actual source file.

If the output file is being made in the given format, the
region is @emph{ignored}.  Otherwise, it is included.

There is one exception (for historical compatibility):
@code{@@ifnotinfo} text is omitted for both Info and plain text
output, not just Info.  To specify text which appears only in Info and
not in plain text, use @code{@@ifnotplaintext}, like this:

@example
@@ifinfo
@@ifnotplaintext
This will be in Info, but not plain text.
@@end ifnotplaintext
@@end ifinfo
@end example

The regions delimited by these commands are ordinary Texinfo source as
with @code{@@iftex}, not raw formatter source as with @code{@@tex}
(@pxref{Raw Formatter Commands}).

@node Raw Formatter Commands
@section Raw Formatter Commands
@cindex Raw formatter commands

@cindex @TeX{} commands, using ordinary
@cindex Ordinary @TeX{} commands, using
@cindex Commands using raw @TeX{}
@cindex Plain @TeX{}

The @code{@@if@dots{}} conditionals just described must be used only
with normal Texinfo source.  For instance, most features of plain
@TeX{} will not work within @code{@@iftex}.  The purpose of
@code{@@if@dots{}} is to provide conditional processing for Texinfo
source, not provide access to underlying formatting features.  For
that, Texinfo provides so-called @dfn{raw formatter commands}.  They
should only be used when truly required (most documents do not need
them).

@findex tex
@cindex Category codes, of plain @TeX{}
The first raw formatter command is @code{@@tex}.  You can enter plain
@TeX{} completely, and use @samp{\} in the @TeX{} commands, by
delineating a region with the @code{@@tex} and @code{@@end tex}
commands.  All plain @TeX{} commands and category codes are restored
within a @code{@@tex} region.  The sole exception is that the
@code{@@} character still introduces a command, so that @code{@@end
tex} can be recognized.  Texinfo processors will not output material
in such a region, unless @TeX{} output is being produced.

@findex \gdef @r{within @code{@@tex}}
@findex \globaldefs @r{within @code{@@tex}}
In complex cases, you may wish to define new @TeX{} macros within
@code{@@tex}.  You must use @code{\gdef} to do this, not @code{\def},
because @code{@@tex} regions are processed in a @TeX{} group.  If you
need to make several definitions, you may wish to set
@code{\globaldefs=1} (its value will be restored to zero as usual when
the group ends at @code{@@end tex}, so it won't cause problems with
the rest of the document).

@cindex Equation, displayed, in plain @TeX{}
@cindex Displayed equation, in plain @TeX{}
As an example, here is a displayed equation written in plain @TeX{}:

@example
@@tex
$$ \chi^2 = \sum_@{i=1@}^N
         \left (y_i - (a + b x_i)
         \over \sigma_i\right)^2 $$
@@end tex
@end example

@noindent
The output of this example will appear only in a printed manual.  If
you are reading this in a format not generated by @TeX{}, you will not
see the equation that appears in the printed manual.

@tex
$$ \chi^2 = \sum_{i=1}^N
         \left(y_i - (a + b x_i)
         \over \sigma_i\right)^2 $$
@end tex

@cindex HTML, including raw
@findex ifhtml
@findex html
Analogously, you can use @code{@@ifhtml @dots{} @@end ifhtml} to
delimit Texinfo source to be included in HTML output only, and
@code{@@html @dots{} @@end html} for a region of raw HTML.

@cindex XML, including raw
@findex ifxml
@findex xml
Likewise, you can use @code{@@ifxml @dots{} @@end ifxml} to delimit
Texinfo source to be included in XML output only, and @code{@@xml
@dots{} @@end xml} for a region of raw XML@.  Regions of raw text in
other formats will also be present in the XML output, but with
protection of XML characters and within corresponding elements.  For
example, the raw HTML text:

@example
@group
@@html
<br />
@@end html
@end group
@end example

@noindent
will be included in the XML output as:

@example
@group
<html>
<br />
</html>
@end group
@end example

@cindex Docbook, including raw
@findex ifdocbook
@findex docbook
Again likewise, you can use @code{@@ifdocbook @dots{} @@end ifdocbook}
to delimit Texinfo source to be included in Docbook output only, and
@code{@@docbook @dots{} @@end docbook} for a region of raw Docbook.

The behavior of newlines in raw regions is unspecified.

In all cases, in raw processing, @code{@@} retains the same meaning as
in the remainder of the document.  Thus, the Texinfo processors must
recognize and even execute, to some extent, the contents of the raw
regions, regardless of the final output format.  Therefore, specifying
changes that globally affect the document inside a raw region leads to
unpredictable and generally undesirable behavior.  For example, using
the @code{@@kbdinputstyle} command inside a raw region is undefined.

The remedy is simple: don't do that.  Use the raw formatter commands
for their intended purpose, of providing material directly in the
underlying format.  When you simply want to give different Texinfo
specifications for different output formats, use the
@code{@@if@dots{}} conditionals and stay in Texinfo syntax.

@node Inline Conditionals
@section Inline Conditionals: @code{@@inline}, @code{@@inlineifelse}, @code{@@inlineraw}
@findex inlinefmt
@findex inlinefmtifelse
@findex inlineraw
@cindex Inline conditionals
@cindex Conditional commands, inline
@cindex Brace-delimited conditional text
@cindex Newlines, avoiding in conditionals
@cindex Whitespace, controlling in conditionals

Texinfo provides a set of conditional commands with arguments given
within braces:

@table @code
@item @@inlinefmt@{@var{format}, @var{text}@}
Process the Texinfo @var{text} if @var{format} output is being
generated.

@item @@inlinefmtifelse@{@var{format}, @var{then-text}, @var{else-text}@}
Process the Texinfo @var{then-text} if @var{format} output is being
generated; otherwise, process @var{else-text}.

@item @@inlineraw@{@var{format}, @var{text}@}
Similar, but for raw @var{text} (@pxref{Raw Formatter Commands}).
@end table

The supported @var{format} names are:

@example
docbook  html  info  plaintext  tex  xml
@end example

For example,

@example
@@inlinefmt@{html, @@emph@{HTML-only text@}@}
@end example

@noindent is nearly equivalent to

@example
@@ifhtml
@@emph@{HTML-only text@}
@@end ifhtml
@end example

@noindent except that no whitespace is added, as happens in the latter
(environment) case.

In these commands, whitespace is ignored after the comma separating
the arguments, as usual, but is @emph{not} ignored at the end of
@var{text}.

To insert a literal at sign, left brace, or right brace in one of the
arguments, you must use the alphabetic commands @code{@@atchar@{@}}
(@pxref{Inserting an Atsign}), and @code{@@lbracechar@{@}} or
@code{@@rbracechar@{@}} (@pxref{Inserting Braces}), or the parsing
will become confused.

With @code{@@inlinefmtifelse}, it is also necessary to use
@code{@@comma@{@}} to avoid mistaking a @samp{,} in the text for the
delimiter.  With @code{@@inlinefmt} and @code{@@inlineraw},
@code{@@comma@{@}} is not required (though it's fine to use it), since
these commands always have exactly two arguments.

For @TeX{}, the processed @var{text} cannot contain newline-delimited
commands.  Text to be ignored (i.e., for non-@TeX{}) can, though.

Two other @code{@@inline...} conditionals complement the
@code{@@ifset} and @code{@@ifclear} commands; see the next section.

@node @code{@@set @@clear @@value}
@section Flags: @code{@@set}, @code{@@clear}, conditionals, and @code{@@value}

@anchor{set clear value}@c old name
You can direct the Texinfo formatting commands to format or ignore parts
of a Texinfo file with the @code{@@set}, @code{@@clear}, @code{@@ifset},
and @code{@@ifclear} commands.

Here are brief descriptions of these commands, see the following
sections for more details:

@table @code
@item @@set @var{flag} [@var{value}]
Set the variable @var{flag}, to the optional @var{value} if specified.

@item @@clear @var{flag}
Undefine the variable @var{flag}, whether or not it was previously defined.

@item @@ifset @var{flag}
If @var{flag} is set, text through the next @code{@@end ifset} command
is formatted.  If @var{flag} is clear, text through the following
@code{@@end ifset} command is ignored.

@item @@inlineifset@{@var{flag}, @var{text}@}
Brace-delimited version of @code{@@ifset}.

@item @@ifclear @var{flag}
If @var{flag} is set, text through the next @code{@@end ifclear} command
is ignored.  If @var{flag} is clear, text through the following
@code{@@end ifclear} command is formatted.

@item @@inlineifclear@{@var{flag}, @var{text}@}
Brace-delimited version of @code{@@ifclear}.

@end table

@menu
* @code{@@set @@value}::                 Expand a flag variable to a string.
* @code{@@ifset @@ifclear}::             Format a region if a flag is set.
* @code{@@inlineifset @@inlineifclear}:: Brace-delimited flag conditionals.
* @code{@@value} Example::              An easy way to update edition information.
@end menu

@node @code{@@set @@value}
@subsection @code{@@set} and @code{@@value}

@anchor{set value}@c old name
@findex set
@findex value
@findex clear

You use the @code{@@set} command to specify a value for a flag, which
is later expanded by the @code{@@value} command.

A @dfn{flag} (aka @dfn{variable}) name is an identifier starting with
an alphanumeric, @samp{-}, or @samp{_}.  Subsequent characters, if
any, may not be whitespace, @samp{@@}, braces, angle brackets, or any
of @samp{~`^+|}; other characters, such as @samp{%}, may work.
However, it is best to use only letters and numerals in a flag name,
not @samp{-} or @samp{_} or others---they will work in some contexts,
but not all, due to limitations in @TeX{}.

The value is the remainder of the input line, and can contain anything.
However, unlike most other commands which take the rest of the line as
a value, @code{@@set} need not appear at the beginning of a line.

Write the @code{@@set} command like this:

@example
@@set foo This is a string.
@end example

@noindent
This sets the value of the flag @code{foo} to ``This is a string.''.

The Texinfo formatters then replace a @code{@@value@{@var{flag}@}}
command with the string to which @var{flag} is set.  Thus, when
@code{foo} is set as shown above, the Texinfo formatters convert this:

@example
@group
@@value@{foo@}
@exdent @r{to this:}
This is a string.
@end group
@end example

You can write a @code{@@value} command within a paragraph; but you
must write a @code{@@set} command on a line of its own.

If you write the @code{@@set} command like this:

@example
@@set foo
@end example

@noindent
without specifying a string, the value of @code{foo} is the empty string.

If you clear a previously set flag with @code{@@clear @var{flag}}, a
subsequent @code{@@value@{flag@}} command will report an error.

For example, if you set @code{foo} as follows:

@example
@@set howmuch very, very, very
@end example

@noindent
then the formatters transform

@example
@group
It is a @@value@{howmuch@} wet day.
@exdent @r{into}
It is a very, very, very wet day.
@end group
@end example

If you write

@example
@@clear howmuch
@end example

@noindent
then the formatters transform

@example
@group
It is a @@value@{howmuch@} wet day.
@exdent @r{into}
It is a @{No value for "howmuch"@} wet day.
@end group
@end example

@code{@@value} cannot be reliably used as the argument to an accent
command (@pxref{Inserting Accents}).  For example, this fails:

@example
@@set myletter a
@@'@@value@{myletter@}    @c fails!
@end example

@node @code{@@ifset @@ifclear}
@subsection @code{@@ifset} and @code{@@ifclear}

@anchor{ifset ifclear}@c old name
@findex ifset

When a @var{flag} is set, the Texinfo formatting commands format text
between subsequent pairs of @code{@@ifset @var{flag}} and @code{@@end
ifset} commands.  When the @var{flag} is cleared, the Texinfo formatting
commands do @emph{not} format the text.  @code{@@ifclear} operates
analogously.

Write the conditionally formatted text between @code{@@ifset @var{flag}}
and @code{@@end ifset} commands, like this:

@example
@group
@@ifset @var{flag}
@var{conditional-text}
@@end ifset
@end group
@end example

For example, you can create one document that has two variants, such as
a manual for a `large' and `small' model:

@cindex Shrubbery
@example
You can use this machine to dig up shrubs
without hurting them.

@@set large

@@ifset large
It can also dig up fully grown trees.
@@end ifset

Remember to replant promptly @dots{}
@end example

@noindent
In the example, the formatting commands will format the text between
@code{@@ifset large} and @code{@@end ifset} because the @code{large}
flag is set.

When @var{flag} is cleared, the Texinfo formatting commands do
@emph{not} format the text between @code{@@ifset @var{flag}} and
@code{@@end ifset}; that text is ignored and does not appear in either
printed or Info output.

For example, if you clear the flag of the preceding example by writing
an @code{@@clear large} command after the @code{@@set large} command
(but before the conditional text), then the Texinfo formatting commands
ignore the text between the @code{@@ifset large} and @code{@@end ifset}
commands.  In the formatted output, that text does not appear; in both
printed and Info output, you see only the lines that say, ``You can use
this machine to dig up shrubs without hurting them.  Remember to replant
promptly @dots{}''.

@findex ifclear
If a flag is cleared with a @code{@@clear @var{flag}} command, then
the formatting commands format text between subsequent pairs of
@code{@@ifclear} and @code{@@end ifclear} commands.  But if the flag
is set with @code{@@set @var{flag}}, then the formatting commands do
@emph{not} format text between an @code{@@ifclear} and an @code{@@end
ifclear} command; rather, they ignore that text.  An @code{@@ifclear}
command looks like this:

@example
@@ifclear @var{flag}
@end example

@node @code{@@inlineifset @@inlineifclear}
@subsection @code{@@inlineifset} and @code{@@inlineifclear}

@findex inlineifset
@findex inlineifclear
@cindex Flag conditionals, brace-delimited
@cindex Brace-delimited flag conditionals

@code{@@inlineifset} and @code{@@inlineifclear} provide
brace-delimited alternatives to the @code{@@ifset} and
@code{@@ifclear} forms, similar to the other @code{@@inline...}
Commands (@pxref{Inline Conditionals}).  The same caveats about
argument parsing given there apply here too.

@table @code
@item @@inlineifset@{@var{var}, @var{text}@}
Process the Texinfo @var{text} if the flag @var{var} is defined.

@item @@inlineifclear@{@var{var}, @var{text}@}
Process the Texinfo @var{text} if the flag @var{var} is not defined.
@end table

Except for the syntax, their general behavior and purposes is the same
as with @code{@@ifset} and @code{@@ifclear}, described in the previous
section.

@node @code{@@value} Example
@subsection @code{@@value} Example

@anchor{value Example}@c old name

You can use the @code{@@value} command to minimize the number of
places you need to change when you record an update to a manual.
@xref{GNU Sample Texts}, for the full text of an example of using this
to work with Automake distributions.

This example is adapted from @ref{Top,,, make, The GNU Make Manual}.

@enumerate
@item
Set the flags:

@example
@group
@@set EDITION 0.35 Beta
@@set VERSION 3.63 Beta
@@set UPDATED 14 August 1992
@@set UPDATE-MONTH August 1992
@end group
@end example

@item
Write text for the @code{@@copying} section (@pxref{@code{@@copying}}):

@example
@group
@@copying
This is Edition @@value@{EDITION@},
last updated @@value@{UPDATED@},
of @@cite@{The GNU Make Manual@},
for @@code@{make@}, version @@value@{VERSION@}.

Copyright @dots{}

Permission is granted @dots{}
@@end copying
@end group
@end example

@item
Write text for the title page, for people reading the printed manual:

@example
@group
@@titlepage
@@title GNU Make
@@subtitle A Program for Directing Recompilation
@@subtitle Edition @@value@{EDITION@}, @dots{}
@@subtitle @@value@{UPDATE-MONTH@}
@@page
@@insertcopying
@dots{}
@@end titlepage
@end group
@end example

@noindent
(On a printed cover, a date listing the month and the year looks less
fussy than a date listing the day as well as the month and year.)

@item
Write text for the Top node, for people reading the Info file:

@example
@group
@@ifnottex
@@node Top
@@top Make

This is Edition @@value@{EDITION@},
last updated @@value@{UPDATED@},
of @@cite@{The GNU Make Manual@},
for @@code@{make@}, version @@value@{VERSION@}.
@@end ifnottex
@end group
@end example

After you format the manual, the @code{@@value} constructs have been
expanded, so the output contains text like this:

@example
@group
This is Edition 0.35 Beta, last updated 14 August 1992,
of `The GNU Make Manual', for `make', Version 3.63 Beta.
@end group
@end example
@end enumerate

When you update the manual, you change only the values of the flags; you
do not need to edit the three sections.

@node Testing for Texinfo Commands
@section Testing for Texinfo Commands: @code{@@ifcommanddefined}, @code{@@ifcommandnotdefined}

@cindex Testing for Texinfo commands
@cindex Checking for Texinfo commands
@cindex Texinfo commands, testing for
@cindex Commands, testing for Texinfo
@cindex Versions of Texinfo, adapting to
@cindex Features of Texinfo, adapting to
@findex ifcommanddefined
@findex ifcommandnotdefined

Occasionally, you may want to arrange for your manual to test if a
given Texinfo command is available and (presumably) do some sort of
fallback formatting if not.  There are conditionals
@code{@@ifcommanddefined} and @code{@@ifcommandnotdefined} to do this.
For example:

@example
@@ifcommanddefined node
Good, @@samp@{@@@@node@} is defined.
@@end ifcommanddefined
@end example

@noindent will output the expected `Good, @samp{@@node} is defined.'.

This conditional will also consider any new commands defined by
the document via @code{@@macro}, @code{@@alias},
@code{@@definfoenclose}, and @code{@@def@r{(}code@r{)}index}
(@pxref{Defining New Texinfo Commands}) to be true.  Caveat: the @TeX{}
implementation reports internal @TeX{} commands, in addition to all
the Texinfo commands, as being ``defined''; the @code{makeinfo}
implementation is reliable in this regard, however.

@pindex @file{NEWS} file for Texinfo
You can check the @file{NEWS} file in the Texinfo source distribution
and linked from the Texinfo home page
(@url{http://www.gnu.org/software/texinfo}) to see when a particular
command was added.

@vindex txicommandconditionals
These command-checking conditionals themselves were added in
Texinfo@tie{}5.0, released in 2013---decades after Texinfo's
inception.  In order to test if they themselves are available,
the predefined flag @code{txicommandconditionals} can be tested, like
this:

@example
@@ifset txicommandconditionals
@@ifcommandnotdefined foobarnode
(Good, @@samp@{@@@@foobarnode@} is not defined.)
@@end ifcommandnotdefined
@@end ifset
@end example

Since flags (see the previous section) were added early in the
existence of Texinfo, there is no problem with assuming they are
available.

We recommend avoiding these tests whenever possible---which is usually
the case.  For many software packages, it is reasonable for all
developers to have a given version of Texinfo (or newer) installed,
and thus no reason to worry about older versions.  (It is
straightforward for anyone to download and install the Texinfo source;
it does not have any problematic dependencies.)

The issue of Texinfo versions does not generally arise for end-users.
With properly distributed packages, users need not process the Texinfo
manual simply to build and install the package; they can use
preformatted Info (or other) output files.  This is desirable in
general, to avoid unnecessary dependencies between packages
(@pxref{Releases,,, standards, GNU Coding Standards}).

@node Conditional Nesting
@section Conditional Nesting
@cindex Conditionals, nested
@cindex Nesting conditionals

Conditionals can be nested; however, the details are a little tricky.
The difficulty comes with failing conditionals, such as
@code{@@ifhtml} when HTML is not being produced, where the included
text is to be ignored.  However, it is not to be @emph{completely}
ignored, since it is useful to have one @code{@@ifset} inside another,
for example---that is a way to include text only if two conditions are
met.  Here's an example:

@example
@@ifset somevar
@@ifset anothervar
Both somevar and anothervar are set.
@@end ifset
@@ifclear anothervar
Somevar is set, anothervar is not.
@@end ifclear
@@end ifset
@end example

Technically, Texinfo requires that for a failing conditional, the
ignored text must be properly nested with respect to that failing
conditional.  Unfortunately, it's not always feasible to check that
@emph{all} conditionals are properly nested, because then the
processors could have to fully interpret the ignored text, which
defeats the purpose of the command.  Here's an example illustrating
these rules:

@example
@@ifset a
@@ifset b
@@ifclear ok  - ok, ignored
@@end junky   - ok, ignored
@@end ifset
@@c WRONG - missing @@end ifset.
@end example

Finally, as mentioned above, all conditional commands must be on lines
by themselves, with no text (even spaces) before or after.  Otherwise,
the processors cannot reliably determine which commands to consider
for nesting purposes.

@node Defining New Texinfo Commands
@chapter Defining New Texinfo Commands

@cindex Macros
@cindex Defining new Texinfo commands
@cindex New Texinfo commands, defining
@cindex Texinfo commands, defining new
@cindex User-defined Texinfo commands

Texinfo provides several ways to define new commands (in all cases,
it's not recommended to try redefining existing commands):

@itemize @bullet
@item
A Texinfo @dfn{macro} allows you to define a new Texinfo command as any
sequence of text and/or existing commands (including other macros).  The
macro can have any number of @dfn{parameters}---text you supply each
time you use the macro.

Incidentally, these macros have nothing to do with the @code{@@defmac}
command, which is for documenting macros in the subject area of the
manual (@pxref{Def Cmd Template}).

@item
@samp{@@alias} is a convenient way to define a new name for an existing
command.

@item
@samp{@@definfoenclose} allows you to define new commands with
customized output for all non-@TeX{} output formats.

@end itemize

Most generally of all (not just for defining new commands), it is
possible to invoke any external macro processor and have Texinfo
recognize so-called @code{#line} directives for error reporting.

If you want to do simple text substitution, @code{@@set} and
@code{@@value} is the simplest approach (@pxref{@code{@@set @@clear
@@value}}).

@menu
* Defining Macros::             Defining and undefining new commands.
* Invoking Macros::             Using a macro, once you've defined it.
* Macro Details::               Limitations of Texinfo macros.
* @code{@@alias}::                      Command aliases.
* @code{@@definfoenclose}::             Customized highlighting.
* External Macro Processors::   @code{#line} directives.
@end menu

@node Defining Macros
@section Defining Macros
@cindex Defining macros
@cindex Macro definitions, Texinfo

@findex macro
You use the Texinfo @code{@@macro} command to define a macro, like this:

@example
@@macro @var{macroname}@{@var{param1}, @var{param2}, @dots{}@}
@var{text} @dots{} \@var{param1}\ @dots{}
@@end macro
@end example

The @dfn{parameters} @var{param1}, @var{param2}, @dots{} correspond to
arguments supplied when the macro is subsequently used in the document
(described in the next section).

@cindex Macro names, valid characters in
@cindex Names of macros, valid characters of
For a macro to work consistently with @TeX{}, @var{macroname} must
consist entirely of letters: no digits, hyphens, underscores, or other
special characters.  So, we recommend using only letters.  However,
@command{makeinfo} will accept anything consisting of alphanumerics,
and (except as the first character) @samp{-}.  The @samp{_} character
is excluded so that macros can be called inside @code{@@math} without
a following space (@pxref{Inserting Math}).

If a macro needs no parameters, you can define it either with an empty
list (@samp{@@macro foo @{@}}) or with no braces at all (@samp{@@macro
foo}).

@cindex Body of a macro
The definition or @dfn{body} of the macro can contain most Texinfo
commands, including macro invocations.  However, a macro definition
that defines another macro does not work in @TeX{} due to limitations
in the design of @code{@@macro}.

@cindex Parameters to macros
In the macro body, instances of a parameter name surrounded by
backslashes, as in @samp{\@var{param1}\} in the example above, are
replaced by the corresponding argument from the macro invocation.  You
can use parameter names any number of times in the body, including zero.

@cindex Backslash in macros
To get a single @samp{\} in the macro expansion, use @samp{\\}.  Any
other use of @samp{\} in the body yields a warning.

@cindex Spaces in macros
@cindex Whitespace in macros
The newline characters after the @code{@@macro} line and before the
@code{@@end macro} line are ignored, that is, not included in the
macro body.  All other whitespace is treated according to the usual
Texinfo rules.

@cindex Recursive macro invocations
@findex rmacro
To allow a macro to be used recursively, that is, in an argument to a
call to itself, you must define it with @samp{@@rmacro}, like this:

@example
@@rmacro rmac @{arg@}
a\arg\b
@@end rmacro
@dots{}
@@rmac@{1@@rmac@{text@}2@}
@end example

This produces the output `a1atextb2b'.  With @samp{@@macro} instead of
@samp{@@rmacro}, an error message is given.

@findex unmacro
@cindex Macros, undefining
@cindex Undefining macros
You can undefine a macro @var{foo} with @code{@@unmacro @var{foo}}.
It is not an error to undefine a macro that is already undefined.
For example:

@example
@@unmacro foo
@end example

@node Invoking Macros
@section Invoking Macros

@cindex Invoking macros
@cindex Expanding macros
@cindex Running macros
@cindex Macro invocation

After a macro is defined (see the previous section), you can
@dfn{invoke} (use) it in your document like this:

@example
@@@var{macroname} @{@var{arg1}, @var{arg2}, @dots{}@}
@end example

@noindent and the result will be more or less as if you typed the body of
@var{macroname} at that spot.  For example:

@example
@@macro foo @{p, q@}
Together: \p\ & \q\.
@@end macro
@@foo@{a, b@}
@end example

@noindent produces:

@display
Together: a & b.
@end display

@cindex Backslash, and macros
Thus, the arguments and parameters are separated by commas and
delimited by braces; any whitespace after (but not before) a comma is
ignored.  The braces are required in the invocation even when the
macro takes no arguments, consistent with other Texinfo commands.  For
example:

@example
@@macro argless @{@}
No arguments here.
@@end macro
@@argless@{@}
@end example

@noindent produces:

@display
No arguments here.
@end display

@cindex Comma, in macro arguments
Passing macro arguments containing commas requires care, since
commas also separate the arguments.  To include a comma character in
an argument, the most reliable method is to use the @code{@@comma@{@}}
command.  For @code{makeinfo}, you can also prepend a backslash
character, as in @samp{\,}, but this does not work with @TeX{}.

@cindex Automatic quoting of commas for some macros
@cindex Quoting, automatic for some macros
It's not always necessary to worry about commas.  To facilitate use of
macros, @command{makeinfo} implements two rules for @dfn{automatic
quoting} in some circumstances:

@enumerate 1
@item If a macro takes only one argument, all commas in its invocation
are quoted by default.  For example:

@example
@group
@@macro TRYME@{text@}
@@strong@{TRYME: \text\@}
@@end macro

@@TRYME@{A nice feature, though it can be dangerous.@}
@end group
@end example

@noindent
will produce the following output

@example
@strong{TRYME: A nice feature, though it can be dangerous.}
@end example

And indeed, it can.  Namely, @command{makeinfo} does not control the
number of arguments passed to one-argument macros, so be careful when
you invoke them.

@item If a macro invocation includes another command (including a
recursive invocation of itself), any commas in the nested command
invocation(s) are quoted by default.  For example, in

@example
@@say@{@@strong@{Yes, I do@}, person one@}
@end example

the comma after @samp{Yes} is implicitly quoted.  Here's another
example, with a recursive macro:

@example
@group
@@rmacro cat@{a,b@}
\a\\b\
@@end rmacro

@@cat@{@@cat@{foo, bar@}, baz@}
@end group
@end example

@noindent
will produce the string @samp{foobarbaz}.

@item Otherwise, a comma should be explicitly quoted, as above, for it
to be treated as a part of an argument.
@end enumerate

@cindex Backslash, in macro arguments
@cindex Braces, in macro arguments
The backslash itself can be quoted in macro arguments with another
backslash.  For example:

@example
@@@var{macname} @{\\bleh@}
@end example

@noindent
will pass the argument @samp{\bleh} to @var{macname}.

@command{makeinfo} also recognizes @samp{\@{} and @samp{\@}} sequences
for curly braces, but these are not recognized by the implementation in
@TeX{}.  There should, however, rarely be a need for these, as they are
only needed when a macro argument contains unbalanced braces.

If a macro is defined to take exactly one argument, it can be
invoked without any braces, taking all of the line after the macro name
as the argument.  For example:

@example
@@macro bar @{p@}
Twice: \p\ & \p\.
@@end macro
@@bar aah
@end example

@noindent produces:

@display
Twice: aah & aah.
@end display

@noindent
In these arguments, there is no escaping of special characters, so each
@samp{\} stands for itself.

If a macro is defined to take more than one argument, but is called
with only one (in braces), the remaining arguments are set to the
empty string, and no error is given.  For example:

@example
@@macro addtwo @{p, q@}
Both: \p\\q\.
@@end macro
@@addtwo@{a@}
@end example

@noindent produces simply:

@display
Both: a.
@end display

@node Macro Details
@section Macro Details and Caveats
@cindex Macro details
@cindex Details of macro usage
@cindex Caveats for macro usage

@cindex Macro expansion, contexts for
@cindex Expansion of macros, contexts for
By design, macro expansion does not happen in the following contexts
in @command{makeinfo}:

@itemize @bullet
@item @code{@@macro} and @code{@@unmacro} lines;

@item @code{@@if...} lines, including @code{@@ifset} and similar;

@item @code{@@set}, @code{@@clear}, @code{@@value};

@item @code{@@clickstyle} lines;

@item @code{@@end} lines.
@end itemize

@noindent Unfortunately, @TeX{} may do some expansion in these situations,
possibly yielding errors.

Also, quite a few macro-related constructs cause problems with @TeX{};
some of the caveats are listed below.  Thus, if you get macro-related
errors when producing the printed version of a manual, you might try
expanding the macros with @command{makeinfo} by invoking
@command{texi2dvi} with the @samp{-E} option (@pxref{Format with
@command{texi2dvi}}).  Or, more reliably, eschew Texinfo macros altogether
and use a language designed for macro processing, such as M4
(@pxref{External Macro Processors}).

@itemize @bullet
@item
As mentioned earlier, macro names must consist entirely of letters.

@item
It is not advisable to redefine any @TeX{} primitive, plain, or
Texinfo command name as a macro. Unfortunately this is a large and
open-ended set of names, and the possible resulting errors are
unpredictable.

@item
Arguments to macros taking more than one argument cannot cross lines.

@item
Macros containing a command which must be on a line by itself, such as
a conditional, cannot be invoked in the middle of a line.  Similarly,
macros containing line-oriented commands or text, such as
@code{@@example} environments, may behave unpredictably in @TeX{}.

@item
If you have problems using conditionals within a macro, an alternative
is to use separate macro definitions inside conditional blocks.  For
example, instead of

@example
@@macro Mac
@@iftex
text for TeX output
@@end iftex
@@ifnottex
text for not TeX output
@@end ifnottex
@@end macro
@end example

@noindent you can do the following instead:

@example
@@iftex
@@macro Mac
text for TeX output
@@end macro
@@end iftex

@@ifnottex
@@macro Mac
text for not TeX output
@@end macro
@@end ifnottex
@end example

@item
Texinfo commands in the expansion of a macro in the text of an index
entry may end up being typeset as literal text (including an ``@@''
sign), instead of being interpreted with their intended meaning.

@item
White space is ignored at the beginnings of lines.

@item
Macros can't be reliably used in the argument to accent commands
(@pxref{Inserting Accents}).

@item
The backslash escape for commas in macro arguments does not work;
@code{@@comma@{@}} must be used.

@item
Likewise, if you want to pass an argument with the Texinfo command
@code{@@,} (to produce a cedilla, see @ref{Inserting Accents}), you have
to use @code{@@value} or another work-around.  Otherwise, the comma
may be taken as separating the arguments.  For example,

@example
@@macro mactwo@{argfirst, argsecond@}
\argfirst\+\argsecond\.
@@end macro
@@set fc Fran@@,cois
@@mactwo@{@@value@{fc@},@}
@end example

@noindent produces:

@display
Fran@,cois+.
@end display

@c currently @mactwo{Fran@,cois} works in TeX, but @mactwo{Franc@\,cois}
@c works in makeinfo.  better to avoid commas altogether using this trick.
@c an alternative to @, could be invented if needed.

@item
Ending a macro body with @samp{@@c} may cause text following the macro
invocation to be ignored as a comment in @command{makeinfo}.  This is
not the case when processing with @TeX{}.  This was often done
to ``comment out'' an unwanted newline at the end of a macro body, but
this is not necessary any more, as the final newline before @samp{@@end
macro} is not included in the macro body anyway.

@item
In general, you can't arbitrarily substitute a macro (or
@code{@@value}) call for Texinfo command arguments, even when the text
is the same.  Texinfo is not M4 (or even plain @TeX{}).  It might work
with some commands, it fails with others.  Best not to do it at all.
For instance, this fails:

@example
@@macro offmacro
off
@@end macro
@@headings @@offmacro
@end example

@noindent
This looks equivalent to @code{@@headings off}, but for @TeX{}nical
reasons, it fails with a mysterious error message (namely,
@samp{Paragraph ended before @@headings was complete}).

@item
Macros cannot define macros in the natural way.  To do this, you must
use conditionals and raw @TeX{}.  For example:

@example
@@ifnottex
@@macro ctor @{name, arg@}
@@macro \name\
something involving \arg\ somehow
@@end macro
@@end macro
@@end ifnottex
@@tex
\gdef\ctor#1@{\ctorx#1,@}
\gdef\ctorx#1,#2,@{\def#1@{something involving #2 somehow@}@}
@@end tex
@end example
@end itemize

The @command{makeinfo} implementation also has the following
limitations (by design):

@itemize
@item
@code{@@verbatim} and macros do not mix; for instance, you can't start
a verbatim block inside a macro and end it outside
(@pxref{@code{@@verbatim}}).  Starting any environment inside a macro
and ending it outside may or may not work, for that matter.

@item
Macros that completely define macros are ok, but it's not possible to
have incompletely nested macro definitions.  That is, @code{@@macro}
and @code{@@end macro} (likewise for @code{@@rmacro}) must be
correctly paired.  For example, you cannot start a macro definition
within a macro, and then end that nested definition outside the macro.
@end itemize

In the @code{makeinfo} implementation before Texinfo 5.0, ends of
lines from expansion of a @code{@@macro} definition did not end an
@@-command line-delimited argument (@code{@@chapter}, @code{@@center},
etc.).  This is no longer the case.  For example:

@example
@@macro twolines@{@}
aaa
bbb
@@end macro
@@center @@twolines@{@}
@end example

In the current @code{makeinfo}, this is equivalent to:

@example
@@center aaa
bbb
@end example

@noindent with just @samp{aaa} as the argument to @code{@@center}.  In
the earlier implementation, it would have been parsed as this:

@example
@@center aaa bbb
@end example

@node @code{@@alias}
@section @samp{@@alias @var{new}=@var{existing}}

@anchor{alias}@c old name
@cindex Aliases, command
@cindex Command aliases
@findex alias

The @samp{@@alias} command defines a new command to be just like an
existing one.  This is useful for defining additional markup names,
thus preserving additional semantic information in the input even
though the output result may be the same.

Write the @samp{@@alias} command on a line by itself, followed by the
new command name, an equals sign, and the existing command name.
Whitespace around the equals sign is optional and ignored if present.
Thus:

@example
@@alias @var{new} = @var{existing}
@end example

For example, if your document contains citations for both books and
some other media (movies, for example), you might like to define a
macro @code{@@moviecite@{@}} that does the same thing as an ordinary
@code{@@cite@{@}} but conveys the extra semantic information as well.
You'd do this as follows:

@example
@@alias moviecite = cite
@end example

Macros do not always have the same effect as aliases, due to vagaries
of argument parsing.  Also, aliases are much simpler to define than
macros.  So the command is not redundant.

Unfortunately, it's not possible to alias Texinfo environments; for
example, @code{@@alias lang=example} is an error.

Aliases must not be recursive, directly or indirectly.

It is not advisable to redefine any @TeX{} primitive, plain @TeX{}, or
Texinfo command name as an alias.  Unfortunately this is a very large
set of names, and the possible resulting errors from @TeX{} are
unpredictable.

@command{makeinfo} will accept the same identifiers for aliases as it
does for macro names, that is, alphanumerics and (except as the first
character) @samp{-}.

@node @code{@@definfoenclose}
@section @code{@@definfoenclose}: Customized Highlighting

@anchor{definfoenclose}@c old name
@cindex Highlighting, customized
@cindex Customized highlighting
@findex definfoenclose

An @code{@@definfoenclose} command may be used to define a
highlighting command for all the non-@TeX{} output formats.  A command
defined using @code{@@definfoenclose} marks text by enclosing it in
strings that precede and follow the text.  You can use this to get
closer control of your output.

Presumably, if you define a command with @code{@@definfoenclose}, you
will create a corresponding command for @TeX{}, either in
@file{texinfo.tex}, @file{texinfo.cnf}, or within an @samp{@@iftex} or
@samp{@@tex} in your document.

Write a @code{@@definfoenclose} command at the beginning of a line
followed by three comma-separated arguments.  The first argument to
@code{@@definfoenclose} is the @@-command name (without the
@code{@@}); the second argument is the start delimiter string; and the
third argument is the end delimiter string.  The latter two arguments
enclose the highlighted text in the output.

A delimiter string may contain spaces.  Neither the start nor end
delimiter is required.  If you do not want a start delimiter but do
want an end delimiter, you must follow the command name with two
commas in a row; otherwise, the end delimiter string you intended will
naturally be (mis)interpreted as the start delimiter string.

If you do a @code{@@definfoenclose} on the name of a predefined
command (such as @code{@@emph}, @code{@@strong}, @code{@@t}, or
@code{@@i}), the enclosure definition will override the built-in
definition.  We don't recommend this.

An enclosure command defined this way takes one argument in braces,
since it is intended for new markup commands (@pxref{Marking Text}).

@findex phoo
For example, you can write:

@example
@@definfoenclose phoo,//,\\
@end example

@noindent
near the beginning of a Texinfo file to define @code{@@phoo} as an Info
formatting command that inserts `//' before and `\\' after the argument
to @code{@@phoo}.  You can then write @code{@@phoo@{bar@}} wherever you
want `//bar\\' highlighted in Info.

For @TeX{} formatting, you could write

@example
@@iftex
@@global@@let@@phoo=@@i
@@end iftex
@end example

@noindent
to define @code{@@phoo} as a command that causes @TeX{} to typeset the
argument to @code{@@phoo} in italics.

Each definition applies to its own formatter: one for @TeX{}, the
other for everything else.  The raw @TeX{} commands need to be in
@samp{@@iftex}.  @code{@@definfoenclose} command need not be within
@samp{@@ifinfo}, unless you want to use different definitions for
different output formats.

@findex headword
Here is another example: write

@example
@@definfoenclose headword, , :
@end example

@noindent
near the beginning of the file, to define @code{@@headword} as an Info
formatting command that inserts nothing before and a colon after the
argument to @code{@@headword}.

@samp{@@definfoenclose} definitions must not be recursive, directly or
indirectly.

@node External Macro Processors
@section External Macro Processors: Line Directives
@cindex External macro processors
@cindex Macro processors, external

Texinfo macros (and its other text substitution facilities) work fine
in straightforward cases.  If your document needs unusually complex
processing, however, their fragility and limitations can be a problem.
In this case, you may want to use a different macro processor
altogether, such as M4 (@pxref{Top,,, m4, M4}) or CPP (@pxref{Top,,,
cpp, The C Preprocessor}).

With one exception, Texinfo does not need to know whether its input is
``original'' source or preprocessed from some other source file.
Therefore, you can arrange your build system to invoke whatever
programs you like to handle macro expansion or other preprocessing
needs.  Texinfo does not offer built-in support for any particular
preprocessor, since no one program seemed likely to suffice for the
requirements of all documents.

@cindex Line numbers, in error messages
@cindex Error messages, line numbers in
The one exception is line numbers in error messages.  In that case,
the line number should refer to the original source file, whatever it
may be.  There's a well-known mechanism for this: the so-called
@samp{#line} directive.  Texinfo supports this.

@menu
* @samp{#line} Directive::
* TeX: @samp{#line} and @TeX{}.
* Syntax: @samp{#line} Syntax Details.
@end menu

@node @samp{#line} Directive
@subsection @samp{#line} Directive

@cindex @samp{#line} directive

An input line such as this:

@example
@hashchar{}line 100 "foo.ptexi"
@end example

@noindent indicates that the next line was line 100 of the file
@file{foo.ptexi}, and so that's what an error message should refer to.
Both M4 (@pxref{Preprocessor features,,, m4, GNU M4}) and CPP
(@pxref{Line Control,,, cpp, The C Preprocessor}, and
@ref{Preprocessor Output,,, cpp, The C Preprocessor}) can generate
such lines.

@vindex CPP_LINE_DIRECTIVES
The @command{makeinfo} program recognizes these lines by default,
except within @code{@@verbatim} blocks (@pxref{@code{@@verbatim}}.
Their recognition can be turned off completely with
@code{CPP_LINE_DIRECTIVES} (@pxref{Other Customization Variables}),
though there is normally no reason to do so.

For those few programs (M4, CPP, Texinfo) which need to document
@samp{#line} directives and therefore have examples which would
otherwise match the pattern, the command @code{@@hashchar@{@}} can be
used (@pxref{Inserting a Hashsign}).  The example line above looks
like this in the source for this manual:

@example
@@hashchar@{@}line 100 "foo.ptexi"
@end example

The @code{@@hashchar} command was added to Texinfo in 2013.  If you
don't want to rely on it, you can also use @code{@@set} and
@code{@@value} to insert the literal @samp{#}:

@example
@@set hash #
@@value@{hash@}line 1 "example.c"
@end example

Or, if suitable, a @code{@@verbatim} environment can be used instead
of @code{@@example}.  As mentioned above, @code{#line}-recognition is
disabled inside verbatim blocks.

@node @samp{#line} and @TeX{}
@subsection @samp{#line} and @TeX{}

@cindex @TeX{} and @samp{#line} directives
@cindex @samp{#line} directives, not processing with @TeX{}

As mentioned, @command{makeinfo} recognizes the @samp{#line}
directives described in the previous section.  However,
@file{texinfo.tex} does not and cannot.  Therefore, such a line will
be incorrectly typeset verbatim if @TeX{} sees it.  The solution is to
use @command{makeinfo}'s macro expansion options before running
@TeX{}.  There are three approaches:

@itemize @bullet
@item
If you run @command{texi2dvi} or its variants (@pxref{Format with
@command{texi2dvi}}), you can pass @option{-E} and @command{texi2dvi}
will run @command{makeinfo} first to expand macros and eliminate
@samp{#line}.

@item
If you run @command{makeinfo} or its variants (@pxref{Generic
Translator @command{texi2any}}), you can specify @option{--no-ifinfo
--iftex -E somefile.out}, and then give @file{somefile.out} to
@code{texi2dvi} in a separate command.

@item
Or you can run @option{makeinfo --dvi --Xopt -E}.  (Or @option{--pdf}
instead of @option{--dvi}.)  @command{makeinfo} will then call
@command{texi2dvi -E}.
@end itemize

@findex errormsg@r{, and line numbers in @TeX{}}
One last caveat regarding use with @TeX{}: since the @code{#line}
directives are not recognized, the line numbers emitted by the
@code{@@errormsg@{@}} command (@pxref{Conditional Commands}), or by
@TeX{} itself, are the (incorrect) line numbers from the derived file
which @TeX{} is reading, rather than the preprocessor-specified line
numbers.  This is another example of why we recommend running
@command{makeinfo} for the best diagnostics (@pxref{@command{makeinfo}
Advantages}).

@node @samp{#line} Syntax Details
@subsection @samp{#line} Syntax Details

@cindex @samp{#line} syntax details
@cindex Syntax details, @samp{#line}
@cindex Regular expression, for @samp{#line}

Syntax details for the @samp{#line} directive: the @samp{#} character
can be preceded or followed by whitespace, the word @samp{line} is
optional, and the file name can be followed by a whitespace-separated
list of integers (these are so-called ``flags'' output by CPP in some
cases).  For those who like to know the gory details, the actual
(Perl) regular expression which is matched is this:

@example
/^\s*#\s*(line)? (\d+)(( "([^"]+)")(\s+\d+)*)?\s*$/
@end example

As far as we've been able to tell, the trailing integer flags only
occur in conjunction with a filename, so that is reflected in the
regular expression.

As an example, the following is a syntactically valid @samp{#line}
directive, meaning line 1 of @file{/usr/include/stdio.h}:

@example
@hashchar{} 1 "/usr/include/stdio.h" 2 3 4
@end example

Unfortunately, the quoted filename (@samp{"..."}) has to be optional,
because M4 (especially) can often generate @samp{#line} directives
within a single file.  Since the @samp{line} is also optional, the
result is that lines might match which you wouldn't expect, e.g.,

@example
@hashchar{} 1
@end example

The possible solutions are described above (@pxref{@samp{#line} Directive}).

@node Include Files
@chapter Include Files

@cindex Include files

When a Texinfo processor sees an @code{@@include} command in a Texinfo
file, it processes the contents of the file named by the
@code{@@include} and incorporates them into the output files being
created.  Include files thus let you keep a single large document as a
collection of conveniently small parts.

@menu
* Using Include Files::         How to use the @code{@@include} command.
* @code{texinfo-multiple-files-update}:: How to create and update nodes and
                                     menus when using included files.
* Include Files Requirements::  @code{texinfo-multiple-files-update} needs.
* Sample Include File::         A sample outer file with included files
                                     within it; and a sample included file.
* @code{@@verbatiminclude}::            Including a file verbatim.
* Include Files Evolution::     How use of the @code{@@include} command
                                     has changed over time.
@end menu

@node Using Include Files
@section How to Use Include Files

@findex include

To include another file within a Texinfo file, write the
@code{@@include} command at the beginning of a line and follow it on
the same line by the name of a file to be included.  For example:

@example
@@include buffers.texi
@end example

@@-commands are expanded in file names.  The one most likely to be
useful is @code{@@value} (@pxref{@code{@@set @@value}}), and even then
only in complicated situations.

An included file should simply be a segment of text that you expect to
be included as is into the overall or @dfn{outer} Texinfo file; it
should not contain the standard beginning and end parts of a Texinfo
file.  In particular, you should not start an included file with a
line saying @samp{\input texinfo}; if you do, that text is inserted
into the output file literally.  Likewise, you should not end an
included file with a @code{@@bye} command; nothing after @code{@@bye}
is formatted.

In the long-ago past, you were required to write an
@code{@@setfilename} line at the beginning of an included file, but no
longer.  Now, it does not matter whether you write such a line.  If an
@code{@@setfilename} line exists in an included file, it is ignored.

@node @code{texinfo-multiple-files-update}
@section @code{texinfo-multiple-files-update}

@findex texinfo-multiple-files-update

GNU Emacs Texinfo mode provides the
@code{texinfo-multiple-files-update} command.  This command creates or
updates `Next', `Previous', and `Up' pointers of included files as
well as those in the outer or overall Texinfo file, and it creates or
updates a main menu in the outer file.  Depending on whether you call
it with optional arguments, the command updates only the pointers in
the first @code{@@node} line of the included files or all of them:

@table @kbd
@item M-x texinfo-multiple-files-update
Called without any arguments:

@itemize @minus
@item
Create or update the `Next', `Previous', and `Up' pointers of the
first @code{@@node} line in each file included in an outer or overall
Texinfo file.

@item
Create or update the `Top' level node pointers of the outer or
overall file.

@item
Create or update a main menu in the outer file.
@end itemize

@item C-u M-x texinfo-multiple-files-update
Called with @kbd{C-u} as a prefix argument:

@itemize @minus{}
@item
Create or update pointers in the first @code{@@node} line in each
included file.

@item
Create or update the `Top' level node pointers of the outer file.

@item
Create and insert a master menu in the outer file.  The master menu
is made from all the menus in all the included files.
@end itemize

@item C-u 8 M-x texinfo-multiple-files-update
Called with a numeric prefix argument, such as @kbd{C-u 8}:

@itemize @minus
@item
Create or update @emph{all} the `Next', `Previous', and `Up' pointers
of all the included files.

@item
Create or update @emph{all} the menus of all the included
files.

@item
Create or update the `Top' level node pointers of the outer or
overall file.

@item
And then create a master menu in the outer file.  This is similar to
invoking @code{texinfo-master-menu} with an argument when you are
working with just one file.
@end itemize
@end table

Note the use of the prefix argument in interactive use: with a regular
prefix argument, just @w{@kbd{C-u}}, the
@code{texinfo-multiple-files-update} command inserts a master menu;
with a numeric prefix argument, such as @kbd{C-u 8}, the command
updates @emph{every} pointer and menu in @emph{all} the files and
then inserts a master menu.

@node Include Files Requirements
@section Include Files Requirements
@cindex Include files requirements
@cindex Requirements for include files

If you plan to use the @code{texinfo-multiple-files-update} command,
the outer Texinfo file that lists included files within it should
contain nothing but the beginning and end parts of a Texinfo file, and
a number of @code{@@include} commands listing the included files.  It
should not even include indices, which should be listed in an included
file of their own.

Moreover, each of the included files must contain exactly one highest
level node (conventionally, @code{@@chapter} or equivalent),
and this node must be the first node in the included file.
Furthermore, each of these highest level nodes in each included file
must be at the same hierarchical level in the file structure.
Usually, each is a @code{@@chapter}, an @code{@@appendix}, or an
@code{@@unnumbered} node.  Thus, normally, each included file contains
one, and only one, chapter or equivalent-level node.

The outer file should contain only @emph{one} node, the `Top' node.  It
should @emph{not} contain any nodes besides the single `Top' node.  The
@code{texinfo-multiple-files-update} command will not process
them.

@node Sample Include File
@section Sample File with @code{@@include}
@cindex Sample @code{@@include} file
@cindex Include file sample
@cindex @code{@@include} file sample

Here is an example of an outer Texinfo file with @code{@@include} files
within it before running @code{texinfo-multiple-files-update}, which
would insert a main or master menu:

@example
@group
\input texinfo @@c -*-texinfo-*-
@c %**start of header
@@settitle Include Example
@c %**end of header
@end group

... @xref{Sample Texinfo Files}, for
examples of the rest of the frontmatter ...

@group
@@ifnottex
@@node Top
@@top Include Example
@@end ifnottex
@end group

@group
@@include foo.texinfo
@@include bar.texinfo
@@include concept-index.texinfo
@@bye
@end group
@end example

An included file, such as @file{foo.texinfo}, might look like this:

@example
@group
@@node First
@@chapter First Chapter

Contents of first chapter @dots{}
@end group
@end example

The full contents of @file{concept-index.texinfo} might be as simple as this:

@example
@group
@@node Concept Index
@@unnumbered Concept Index

@@printindex cp
@end group
@end example

The outer Texinfo source file for @cite{The GNU Emacs Lisp Reference
Manual} is named @file{elisp.texi}.  This outer file contains a master
menu with 417 entries and a list of 41 @code{@@include}
files.

@node @code{@@verbatiminclude}
@section @code{@@verbatiminclude} @var{file}: Include a File Verbatim

@anchor{verbatiminclude}@c old name
@findex verbatiminclude
@cindex Verbatim, include file
@cindex Including a file verbatim

You can include the exact contents of a file in the document with the
@code{@@verbatiminclude} command:

@example
@@verbatiminclude @var{filename}
@end example

The contents of @var{filename} is printed in a verbatim environment
(@pxref{@code{@@verbatim}}).  Generally, the file is printed exactly
as it is, with all special characters and white space retained.  No
indentation is added; if you want indentation, enclose the
@code{@@verbatiminclude} within @code{@@example}
(@pxref{@code{@@example}}).

The name of the file is taken literally, with a single exception:
@code{@@value@{@var{var}@}} references are expanded.  This makes it
possible to include files in other directories within a distribution,
for instance:

@example
@@verbatiminclude @@value@{top_srcdir@}/NEWS
@end example

@noindent (You still have to get @code{top_srcdir} defined in the
first place.)

For a method on printing the file contents in a smaller font size, see
the end of the section on @code{@@verbatim}.

@node Include Files Evolution
@section Evolution of Include Files

When Info was first created, it was customary to create many small
Info files on one subject.  Each Info file was formatted from its own
Texinfo source file.  This custom meant that Emacs did not need to
make a large buffer to hold the whole of a large Info file when
someone wanted information; instead, Emacs allocated just enough
memory for the small Info file that contained the particular
information sought.  This way, Emacs could avoid wasting memory.

References from one file to another were made by referring to the file
name as well as the node name. (@xref{Other Info Files, , Referring to
Other Info Files}.  Also, see @ref{Four and Five Arguments, ,
@code{@@xref} with Four and Five Arguments}.)

Include files were designed primarily as a way to create a single,
large printed manual out of several smaller Info files.  In a printed
manual, all the references were within the same document, so @TeX{}
could automatically determine the references' page numbers.  The Info
formatting commands used include files only for creating joint
indices; each of the individual Texinfo files had to be formatted for
Info individually.  (Each, therefore, required its own
@code{@@setfilename} line.)

However, because large Info files are now split automatically, it is
no longer necessary to keep them small.

Nowadays, multiple Texinfo files are used mostly for large documents,
such as @cite{The GNU Emacs Lisp Reference Manual}, and for projects
in which several different people write different sections of a
document simultaneously.

In addition, the Info formatting commands have been extended to work
with the @code{@@include} command so as to create a single large Info
file that is split into smaller files if necessary.  This means that
you can write menus and cross-references without naming the different
Texinfo files.

@node Hardcopy
@chapter Formatting and Printing Hardcopy
@cindex Format and print hardcopy
@cindex Printing hardcopy
@cindex Hardcopy, printing it
@cindex Making a printed manual
@cindex Sorting indices
@cindex Indices, sorting
@cindex @TeX{} index sorting

Running the @command{texi2dvi} or @command{texi2pdf} command is the
simplest way to create printable output.  These commands are installed
as part of the Texinfo package.

In more detail, three major shell commands are used to print formatted
output from a Texinfo manual: one converts the Texinfo source into
something printable, a second sorts indices, and a third actually
prints the formatted document.  When you use the shell commands, you
can either work directly in the operating system shell or work within
a shell inside GNU Emacs (or some other computing environment).

If you are using GNU Emacs, you can use commands provided by Texinfo
mode instead of shell commands.  In addition to the three commands to
format a file, sort the indices, and print the result, Texinfo mode
offers key bindings for commands to recenter the output buffer, show the
print queue, and delete a job from the print queue.

Details are in the following sections.

@menu
* Use @TeX{}::                     Use @TeX{} to format for hardcopy.
* Format with @command{texi2dvi}::        The simplest way to format.
* Format with @command{tex}/@command{texindex}::    Formatting with explicit shell commands.
* Print with @command{lpr}::              How to print.
* Within Emacs::                How to format and print from an Emacs shell.
* Texinfo Mode Printing::       How to format and print in Texinfo mode.
* Compile-Command::             How to print using Emacs's compile command.
* Requirements Summary::        @TeX{} formatting requirements summary.
* Preparing for @TeX{}::           What to do before you use @TeX{}.
* Overfull hboxes::             What are and what to do with overfull hboxes.
* @code{@@smallbook}::                  How to print small format books and manuals.
* A4 Paper::                    How to print on A4 or A5 paper.
* @code{@@pagesizes}::                  How to print with customized page sizes.
* Cropmarks and Magnification:: How to print marks to indicate the size
                                 of pages and how to print scaled up output.
* PDF Output::                  Portable Document Format output.
* Obtaining @TeX{}::               How to obtain @TeX{}.
@end menu

@node Use @TeX{}
@section Use @TeX{}

The typesetting program called @TeX{} is used to format a Texinfo
document for printable output.  @TeX{} is a very powerful typesetting
program and, when used correctly, does an exceptionally good job.

@xref{Obtaining @TeX{}}, for information on how to obtain @TeX{}.  It
is not included in the Texinfo package, being a vast suite of software
in itself.

@node Format with @command{texi2dvi}
@section Format with @command{texi2dvi}

@pindex texi2dvi @r{(shell script)}
@cindex DVI, output in

The @code{texi2dvi} program takes care of all the steps for producing
a @TeX{} DVI file from a Texinfo document.  Similarly, @code{texi2pdf}
produces a PDF file.

To run @code{texi2dvi} or @code{texi2pdf} on an input file
@file{foo.texi}, do this (where @samp{prompt$ } is your shell prompt):

@example
prompt$ @kbd{texi2dvi foo.texi}
prompt$ @kbd{texi2pdf foo.texi}
@end example

As shown in this example, the input filenames to @code{texi2dvi} and
@code{texi2pdf} must include any extension, such as @samp{.texi}.
(Under MS-DOS and perhaps in other circumstances, you may need to run
@samp{sh texi2dvi foo.texi} instead of relying on the operating system
to invoke the shell on the @samp{texi2dvi} script.)

For a list of all the options, run @samp{texi2dvi --help}.  Some of the
options are discussed below.

@opindex --pdf@r{, for @command{texi2dvi}}
@pindex pdftexi2dvi
With the @option{--pdf} option, @command{texi2dvi} produces PDF output
instead of DVI (@pxref{PDF Output}), by running @command{pdftex}
instead of @command{tex}.  Alternatively, the command
@command{texi2pdf} is an abbreviation for running @samp{texi2dvi
--pdf}.  The command @command{pdftexi2dvi} is also provided as a
convenience for AUC-@TeX{} (@pxref{Top,,, auctex, AUC-@TeX{}}), as it
prefers to merely prepend @samp{pdf} to DVI producing tools to have
PDF producing tools.

@opindex --dvipdf@r{, for @command{texi2dvi}}
@pindex dvipdfmx
With the @option{--dvipdf} option, @command{texi2dvi} produces PDF
output by running @TeX{} and then a DVI-to-PDF program: if the
@env{DVIPDF} environment variable is set, that value is used, else the
first program extant among @code{dvipdfmx}, @code{dvipdfm},
@code{dvipdf}, @code{dvi2pdf}, @code{dvitopdf}.  This method generally
supports CJK typesetting better than @command{pdftex}.

@opindex --ps@r{, for @command{texi2dvi}}
@pindex dvips
With the @option{--ps} option, @command{texi2dvi} produces PostScript
instead of DVI, by running @command{tex} and then @command{dvips}
(@pxref{Top,,, dvips, Dvips}).  (Or the value of the @env{DVIPS}
environment variable, if set.)

@opindex --language@r{, for @command{texi2dvi}}
@cindex @LaTeX{}, processing with @command{texi2dvi}
@command{texi2dvi} can also be used to process @LaTeX{} files.
Normally @command{texi2dvi} is able to guess the input file language
by its contents and file name extension; however, if it guesses wrong
you can explicitly specify the input language using
@option{--language=@var{lang}} command line option, where @var{lang}
is either @samp{latex} or @samp{texinfo}.

@opindex --command@r{, for @command{texi2dvi}}
One useful option to @code{texi2dvi} is @samp{--command=@var{cmd}}.
This inserts @var{cmd} on a line by itself, after a
@code{@@setfilename} line in a temporary copy of the input file, before
running @TeX{}.  With this, you can specify different printing
formats, such as @code{@@smallbook} (@pxref{@code{@@smallbook}}),
@code{@@afourpaper} (@pxref{A4 Paper}), or @code{@@pagesizes}
(@pxref{@code{@@pagesizes}}), without actually changing the document
source.  (You can also do this on a site-wide basis with
@file{texinfo.cnf}; @pxref{Preparing for @TeX{}}).

The option @option{-E} (equivalently, @option{-e} and
@option{--expand}) does Texinfo macro expansion using
@command{makeinfo} instead of the @TeX{} implementation (@pxref{Macro
Details}).  Each implementation has its own limitations and
advantages.  If this option is used, no line in the source file
may begin with the string @code{@@c@tie{}_texi2dvi} or the
string @code{@@c@tie{}(_texi2dvi)}.

@command{texi2dvi} takes the @option{--build=@var{mode}} option to
specify where the @TeX{} compilation takes place, and, as a
consequence, how auxiliary files are treated.  The build mode
can also be set using the environment variable
@env{TEXI2DVI_BUILD_MODE}.  The valid values for @var{mode} are:

@table @samp
@item local
 Compile in the current directory, leaving all the auxiliary
 files around.  This is the traditional TeX use.

@item tidy
 Compile in a local @code{*.t2d} directory, where the auxiliary files
 are left.  Output files are copied back to the original file.

 Using the @samp{tidy} mode brings several advantages:
 @itemize -
 @item the current directory is not cluttered with plethora of temporary files.
 @item clutter can be even further reduced using @option{--build-dir=dir}: all
   the @code{*.t2d} directories are stored there.
 @item clutter can be reduced to zero using, e.g.,
   @option{--build-dir=/tmp/\$USER.t2d} or @option {--build-dir=\$HOME/.t2d}.
 @item the output file is updated after every successful @TeX{} run, for
   sake of concurrent visualization of the output.  In a @samp{local} build
   the viewer stops during the whole @TeX{} run.
 @item if the compilation fails, the previous state of the output file
   is preserved.
 @item @acronym{PDF} and @acronym{DVI} compilation are kept in separate
   subdirectories
   preventing any possibility of auxiliary file incompatibility.
 @end itemize

 On the other hand, because @samp{tidy} compilation takes place in another
 directory, occasionally @TeX{} won't be able to find some files (e.g., when
 using @code{\graphicspath}): in that case, use @option{-I} to specify the
 additional directories to consider.

@item clean
 Same as @samp{tidy}, but remove the auxiliary directory afterwards.
 Every compilation therefore requires the full cycle.
@end table

@pindex etex
@pindex pdfetex
@command{texi2dvi} will use @command{etex} (or @command{pdfetex}) if
it is available, because it runs faster in some cases, and
provides additional tracing information when debugging
@file{texinfo.tex}.  Nevertheless, this extended version of @TeX{} is
not required, and the DVI output is identical.
(These days, @command{pdftex} and @command{pdfetex} are exactly the
same, but we still run @command{pdfetex} to cater to ancient @TeX{}
installations.)

@cindex filename recorder for @TeX{}
@cindex @samp{\openout} line in log file
@command{texi2dvi} attempts to detect auxiliary files output by @TeX{},
either by using the @option{-recorder} option, or by scanning for
@samp{\openout} in the log file that a run of @TeX{} produces.  You may
control how @command{texi2dvi} does this with the @env{TEXI2DVI_USE_RECORDER}
environment variable.  Valid values are:

@table @samp
@item yes
use the @option{-recorder} option, no checks.

@item no
scan for @samp{\openout} in the log file, no checks.

@item yesmaybe
check whether @option{-recorder} option is supported, and if yes
use it, otherwise check for tracing @samp{\openout} in the log file is
supported, and if yes use it, else it is an error.

@item nomaybe
same as @samp{yesmaybe}, except that the @samp{\openout} trace in log
file is checked first.
@end table

The default is @samp{nomaybe}.  This environment variable is provided
for troubleshooting purposes, and may change or disappear in the future.

@node Format with @command{tex}/@command{texindex}
@section Format with @command{tex}/@command{texindex}

@cindex Shell formatting with @code{tex} and @code{texindex}
@cindex Formatting with @code{tex} and @code{texindex}
@cindex DVI file

You can do the basic formatting of a Texinfo file with the shell
command @code{tex} followed by the name of the Texinfo file.  For
example:

@example
tex foo.texi
@end example

@noindent @TeX{} will produce a @dfn{DVI file} as well as several auxiliary
files containing information for indices, cross-references, etc.  The
DVI file (for @dfn{DeVice Independent} file) can be printed on
virtually any device, perhaps after a further conversion (see the
previous section).

@pindex texindex
The @code{tex} formatting command itself does not sort the indices; it
writes an output file of unsorted index data.  To generate a printed
index after running the @command{tex} command, you first need a sorted
index to work from.  The @command{texindex} command sorts indices.
(@command{texi2dvi}, described in the previous section, runs
@command{tex} and @command{texindex} as necessary.)

@anchor{Names of index files}
@cindex Names of index files
@cindex Index file names
@code{tex} outputs unsorted index files under names following a
standard convention: the name of your main input file with any
@samp{.texi} or similar extension replaced by the two letter index
name.  For example, the raw index output files for the input file
@file{foo.texi} would be, by default, @file{foo.cp}, @file{foo.vr},
@file{foo.fn}, @file{foo.tp}, @file{foo.pg} and @file{foo.ky}.  Those
are exactly the arguments to give to @code{texindex}.

@need 1000
@cindex Wildcards
@cindex Globbing
Instead of specifying all the unsorted index file names explicitly,
it's typical to use @samp{??} as shell wildcards and give the command
in this form:

@example
texindex foo.??
@end example

@noindent
This command will run @code{texindex} on all the unsorted index files,
including any two letter indices that you have defined yourself using
@code{@@defindex} or @code{@@defcodeindex}.  You can safely run
@samp{texindex foo.??} even if there are files with two letter
extensions that are not index files, such as @samp{foo.el}.  The
@code{texindex} command reports but otherwise ignores such files.

For each file specified, @code{texindex} generates a sorted index file
whose name is made by appending @samp{s} to the input file name; for
example, @file{foo.cps} is made from @file{foo.cp}.  The
@code{@@printindex} command looks for a file with that name
(@pxref{Printing Indices & Menus}).  @TeX{} does not read the raw
index output file, and @code{texindex} does not alter it.

After you have sorted the indices, you need to rerun @code{tex} on the
Texinfo file.  This regenerates the output file, this time with
up-to-date index entries.

Finally, you may need to run @code{tex} one more time, to get the page
numbers in the cross-references correct.

To summarize, this is a five step process.  (Alternatively, it's a
one-step process: run @code{texi2dvi}; see the previous section.)

@enumerate
@item
Run @code{tex} on your Texinfo file.  This generates a DVI file (with
undefined cross-references and no indices), and the raw index files
(with two letter extensions).

@item
Run @code{texindex} on the raw index files.  This creates the
corresponding sorted index files (with three letter extensions).

@item
Run @code{tex} again on your Texinfo file.  This regenerates the DVI
file, this time with indices and defined cross-references, but with
page numbers for the cross-references from the previous run, generally
incorrect.

@item
Sort the indices again, with @code{texindex}.

@item
Run @code{tex} one last time.  This time the correct page numbers are
written for the cross-references.
@end enumerate

@menu
* Formatting Partial Documents::
* Details of @command{texindex}::
@end menu

@node Formatting Partial Documents
@subsection Formatting Partial Documents

@cindex Formatting partial documents
@cindex Partial documents, formatting
@cindex Chapters, formatting one at a time
@cindex Auxiliary files, omitting
@cindex Pointer validation, suppressing
@findex novalidate

Sometimes you may wish to print a document while you know it is
incomplete, or to print just one chapter of a document.  In such a
case, the usual auxiliary files that @TeX{} creates and warnings
@TeX{} gives about undefined cross-references are just nuisances.  You
can avoid them with the @code{@@novalidate} command, which you must
give @emph{before} any sectioning or cross-reference commands.

Thus, the beginning of your file would look approximately like this:

@example
\input texinfo
@@novalidate
@dots{}
@end example

@noindent @code{@@novalidate} also turns off validation in
@code{makeinfo}, just like its @code{--no-validate} option
(@pxref{Pointer Validation}).

Furthermore, you need not run @code{texindex} each time after you run
@code{tex}.  The @code{tex} formatting command simply uses whatever
sorted index files happen to exist from a previous use of
@code{texindex}.  If those are out of date, that is usually ok while
you are creating or debugging a document.

@node Details of @command{texindex}
@subsection Details of @command{texindex}

@cindex Braces, in index entries
In Texinfo version 6, released in 2015, the @command{texindex} program
was completely reimplemented.  The principal functional difference is
that index entries beginning with a left brace or right brace
(@samp{@{} resp.@: @samp{@}}) can work properly.  For example, these
simple index entries are processed correctly, including the ``index
initial'' shown in the index:

@example
@@cindex @@@{
@@cindex @@@}
...
@@printindex cp
@end example

@findex \usebracesinindexestrue
However, to enable this behavior, it's necessary (for the time being)
to give a special option to @TeX{} early in a source document:

@example
@@tex
\global\usebracesinindexestrue
@@end tex
@end example

@cindex Sort string, incorrect @samp{|}
This is because the previous @command{texindex} implementation aborted
with an incorrect error message (@samp{No page number in \entry...})
on such index entries when handled in the normal way.  Therefore
@TeX{} wrote out an incorrect ``sort string'' using the @samp{|}
character; this did not affect the text of the entry, but the index
initial was the incorrect @samp{|}, and sorting was not perfect.

Because of that fatal error, and because relatively few documents have
index entries beginning with braces, we want to provide some
transition time for installations to have the new @command{texindex}.
At some point in the future, we'll make @code{\usebracesinindexes}
true by default (the above @TeX{} code will continue to work fine).

@cindex Literate programming, with Texinfo and @code{awk}
@cindex Texinfo, and literate programming
@cindex Robbins, Arnold
@pindex texiwebjr
@pindex ti.twjr
Although not a matter of functionality, readers may be interested to
know that the new @command{texindex} is a literate program
(@url{http://en.wikipedia.org/wiki/Literate_programming}) using
Texinfo for documentation and (portable) @code{awk} for code.  A
single source file, @file{texindex/ti.twjr} in this case, produces the
runnable program, a printable document, and an online document.

The system is called TexiWeb Jr.@: and was created by Arnold
Robbins, who also wrote the new @command{texindex}.  Not
coincidentally, he is also the long-time maintainer of @command{gawk}
(GNU Awk, @pxref{Top,,, gawk, The GNU Awk User's Guide}).  The file
@file{texindex/Makefile.am} shows example usage of the system.

@node Print with @command{lpr}
@section Print with @command{lpr} from Shell

@pindex lpr @r{(DVI print command)}

The way to print a DVI file depends on your system installation.  Two
common ones are @samp{dvips foo.dvi -o} to make a PostScript file
first and then print that, and @samp{lpr -d foo.dvi} to print a DVI
file directly.

For example, the following commands will (probably) suffice to sort
the indices, format, and print this manual using the @code{texi2dvi}
shell script (@pxref{Format with @command{texi2dvi}}).

@example
@group
texi2dvi texinfo.texi
dvips texinfo.dvi -o
lpr texinfo.ps
@end group
@end example

Depending on the @code{lpr} setup on your machine, you might able to
combine the last two steps into @code{lpr -d texinfo.dvi}.

@cindex PCL file, for printing
You can also generate a PDF file by running @code{texi2pdf} instead of
@code{texi2dvi}; a PDF is often directly printable.  Or you can
generate a PCL file by using @code{dvilj} instead of @code{dvips}, if
you have a printer that prefers that format.

@cindex Shell printing, on MS-DOS/MS-Windows
@cindex Printing DVI files, on MS-DOS/MS-Windows
@pindex lpr@r{-d, replacements on MS-DOS/MS-Windows}
@code{lpr} is a standard program on Unix systems, but it is usually
absent on MS-DOS/MS-Windows.  If so, just create a PostScript or PDF
or PCL file, whatever is most convenient, and print that in the usual
way for your machine (e.g., by sending to the appropriate port,
usually @samp{PRN}).

@node Within Emacs
@section Printing From an Emacs Shell
@cindex Print, format from Emacs shell
@cindex Format, print from Emacs shell
@cindex Shell, format, print from
@cindex Emacs shell, format, print from
@cindex GNU Emacs shell, format, print from

You can give formatting and printing commands from a shell within GNU
Emacs, just like any other shell command.  To create a shell within
Emacs, type @kbd{M-x shell} (@pxref{Shell,,, emacs, The GNU Emacs
Manual}).  In this shell, you can format and print the document.
@xref{Hardcopy, , Format and Print Hardcopy}, for details.

You can switch to and from the shell buffer while @code{tex} is
running and do other editing.  If you are formatting a long document
on a slow machine, this can be very convenient.

For example, you can use @code{texi2dvi} from an Emacs shell.  Here is
one way to use @code{texi2pdf} to format and print @cite{Using and
Porting GNU CC} from a shell within Emacs:

@example
@group
texi2pdf gcc.texi
lpr gcc.pdf
@end group
@end example

See the next section for more information about formatting
and printing in Texinfo mode.

@node Texinfo Mode Printing
@section Formatting and Printing in Texinfo Mode
@cindex Region printing in Texinfo mode
@cindex Format and print in Texinfo mode
@cindex Print and format in Texinfo mode

Texinfo mode provides several predefined key commands for @TeX{}
formatting and printing.  These include commands for sorting indices,
looking at the printer queue, killing the formatting job, and
recentering the display of the buffer in which the operations
occur.

@table @kbd
@item C-c C-t C-b
@itemx M-x texinfo-tex-buffer
Run @code{texi2dvi} on the current buffer.

@item C-c C-t C-r
@itemx M-x texinfo-tex-region
Run @TeX{} on the current region.

@item C-c C-t C-i
@itemx M-x texinfo-texindex
Sort the indices of a Texinfo file formatted with
@code{texinfo-tex-region}.

@item C-c C-t C-p
@itemx M-x texinfo-tex-print
Print a DVI file that was made with @code{texinfo-tex-region} or
@code{texinfo-tex-buffer}.

@item C-c C-t C-q
@itemx M-x tex-show-print-queue
Show the print queue.

@item C-c C-t C-d
@itemx M-x texinfo-delete-from-print-queue
Delete a job from the print queue; you will be prompted for the job
number shown by a preceding @kbd{C-c C-t C-q} command
(@code{texinfo-show-tex-print-queue}).

@item C-c C-t C-k
@itemx M-x tex-kill-job
Kill the currently running @TeX{} job started by either
@code{texinfo-tex-region} or @code{texinfo-tex-buffer}, or any other
process running in the Texinfo shell buffer.

@item C-c C-t C-x
@itemx M-x texinfo-quit-job
Quit a @TeX{} formatting job that has stopped because of an error by
sending an @key{x} to it.  When you do this, @TeX{} preserves a record
of what it did in a @file{.log} file.

@item C-c C-t C-l
@itemx M-x tex-recenter-output-buffer
Redisplay the shell buffer in which the @TeX{} printing and formatting
commands are run to show its most recent output.
@end table

@need 1000
Thus, the usual sequence of commands for formatting a buffer is as
follows (with comments to the right):

@example
@group
C-c C-t C-b             @r{Run @code{texi2dvi} on the buffer.}
C-c C-t C-p             @r{Print the DVI file.}
C-c C-t C-q             @r{Display the printer queue.}
@end group
@end example

The Texinfo mode @TeX{} formatting commands start a subshell in Emacs
called the @file{*tex-shell*}.  The @code{texinfo-tex-command},
@code{texinfo-texindex-command}, and @code{tex-dvi-print-command}
commands are all run in this shell.

You can watch the commands operate in the @samp{*tex-shell*} buffer,
and you can switch to and from and use the @samp{*tex-shell*} buffer
as you would any other shell buffer.

@need 1500
The formatting and print commands depend on the values of several variables.
The default values are:

@example
@group
    @r{Variable}                              @r{Default value}

texinfo-texi2dvi-command                  "texi2dvi"
texinfo-tex-command                       "tex"
texinfo-texindex-command                  "texindex"
texinfo-delete-from-print-queue-command   "lprm"
texinfo-tex-trailer                       "@@bye"
tex-start-of-header                       "%**start"
tex-end-of-header                         "%**end"
tex-dvi-print-command                     "lpr -d"
tex-show-queue-command                    "lpq"
@end group
@end example

You can change the values of these variables with the @kbd{M-x
set-variable} command (@pxref{Examining, , Examining and Setting
Variables, emacs, The GNU Emacs Manual}), or with your @file{.emacs}
initialization file (@pxref{Init File, , , emacs, The GNU Emacs
Manual}).

@cindex Customize Emacs package (@t{Development/Docs/Texinfo})
Beginning with version 20, GNU Emacs offers a user-friendly interface,
called @dfn{Customize}, for changing values of user-definable variables.
@xref{Easy Customization, , Easy Customization Interface, emacs, The GNU
Emacs Manual}, for more details about this.  The Texinfo variables can
be found in the @samp{Development/Docs/Texinfo} group, once you invoke
the @kbd{M-x customize} command.

@node Compile-Command
@section Using the Local Variables List
@cindex Local variables
@cindex Compile command for formatting
@cindex Format with the compile command

Yet another way to apply the @TeX{} formatting command to a Texinfo file
is to put that command in a @dfn{local variables list} at the end of the
Texinfo file.  You can then specify the @code{tex} or @code{texi2dvi}
commands as a @code{compile-command} and have Emacs run it by typing
@kbd{M-x compile}.  This creates a special shell called the
@file{*compilation*} buffer in which Emacs runs the compile command.
For example, at the end of the @file{gdb.texi} file, after the
@code{@@bye}, you could put the following:

@example
@group
Local Variables:
compile-command: "texi2dvi gdb.texi"
End:
@end group
@end example

@noindent
This technique is most often used by programmers who also compile programs
this way; see @ref{Compilation, , , emacs, The GNU Emacs Manual}.

@node Requirements Summary
@section @TeX{} Formatting Requirements Summary
@cindex Requirements for formatting
@cindex Minimal requirements for formatting
@cindex Formatting requirements

Every Texinfo file that is to be input to @TeX{} must begin with a
@code{\input} command:

@example
\input texinfo
@end example

@noindent
This instructs @TeX{} to load the macros it needs to process a Texinfo
file.

Every Texinfo file must end with a line that terminates @TeX{}'s
processing and forces out unfinished pages:

@example
@@bye
@end example

Strictly speaking, these two lines are all a Texinfo file needs to be
processed successfully by @TeX{}.

Usually, however, the beginning includes a @code{@@settitle} command
to define the title of the printed manual, a title page, a copyright
page, permissions, and a table of contents.  Besides @code{@@bye}, the
end of a file usually includes indices.  (Not to mention that most
manuals contain a body of text as well.)

For more information, see:

@itemize @bullet
@item @ref{@code{@@settitle}}.
@item @ref{@code{@@setchapternewpage}}.
@item @ref{Headings}.
@item @ref{Titlepage & Copyright Page}.
@item @ref{Printing Indices & Menus}.
@item @ref{Contents}.
@end itemize

@node Preparing for @TeX{}
@section Preparing for @TeX{}
@cindex Preparing for @TeX{}
@cindex @TeX{} input initialization
@cindex @sortas{profile init} @file{.profile} initialization file
@cindex @sortas{cshrc init} @file{.cshrc} initialization file
@cindex Initialization file for @TeX{} input

@TeX{} needs to know where to find the @file{texinfo.tex} file that the
@samp{\input texinfo} command on the first line reads.  The
@file{texinfo.tex} file tells @TeX{} how to handle @@-commands; it is
included in all standard GNU distributions.  The latest version
released for general use is available
from the usual GNU servers and mirrors:

@smalldisplay
@uref{http://ftp.gnu.org/gnu/texinfo/texinfo.tex}
@uref{http://ftpmirror.gnu.org/texinfo/texinfo.tex}
@end smalldisplay

The latest development version is available from the Texinfo source
repository:
@smalldisplay
@uref{http://svn.savannah.gnu.org/viewvc/trunk/doc/texinfo.tex?root=texinfo&view=log}
@end smalldisplay

@pindex texinfo.tex@r{, installing}
@file{texinfo.tex} is essentially a standalone file, and compatibility
is of utmost concern; so, if you need or want to try a newer version
than came with your system, it nearly always suffices to download it
and put it anywhere that @TeX{} will find it (first).  You can replace
any existing @file{texinfo.tex} with a newer version (of course saving
the original in case of disaster).

@pindex epsf.tex@r{, installing}
Also, you should install @file{epsf.tex}, if it is not already installed
from another distribution.  More details are at the end of the description
of the @code{@@image} command (@pxref{Images}).

@cindex European Computer Modern fonts, installing
@cindex EC fonts, installing
@cindex CM-Super fonts, installing
To use quotation marks other than those used in English, you'll need
to have the European Computer Modern fonts (e.g., @file{ecrm1000}) and
(for PDF output) CM-Super fonts (@pxref{Inserting Quotation Marks}).

@pindex feymr10@r{, installing}
@cindex Euro font, installing
To use the @code{@@euro} command, you'll need the @samp{feym*} fonts
(e.g., @file{feymr10}).  @xref{@code{@@euro}}.

All of the above files (and a whole lot more) should be installed by
default in a reasonable @TeX{} installation.

@pindex texinfo.cnf @r{installation}
@cindex Customizing of @TeX{} for Texinfo
@cindex Site-wide Texinfo configuration file
Optionally, you may create a file @file{texinfo.cnf} for site configuration.
This file is read by @TeX{} at the beginning of a Texinfo file.
You can put any commands you like there, according to local site-wide
conventions.  They will be read by @TeX{} when processing any Texinfo
document.  For example, if @file{texinfo.cnf} contains the line
@samp{@@afourpaper} (@pxref{A4 Paper}), then all Texinfo documents
will be processed with that page size in effect.  If you have nothing
to put in @file{texinfo.cnf}, you do not need to create it.

@cindex Environment variable @code{TEXINPUTS}
@vindex TEXINPUTS
If neither of the above locations for these system files suffice, you
can specify the directories explicitly.  For @file{texinfo.tex}, you
can do this by writing the complete path for the file after the
@code{\input} command.  Another way, that works for both
@file{texinfo.tex} and @file{texinfo.cnf} (and any other file @TeX{}
might read), is to set the @code{TEXINPUTS} environment variable in
your @file{.profile} or @file{.cshrc} file.

Whether you use @file{.profile} or @file{.cshrc} depends on
whether you use a Bourne shell-compatible (@code{sh}, @code{bash},
@code{ksh}, @dots{}) or C shell-compatible (@code{csh}, @code{tcsh})
command interpreter, respeictvely.

In a @file{.profile} file, you could use the following @code{sh} command
sequence:

@example
@group
TEXINPUTS=.:/home/me/mylib:
export TEXINPUTS
@end group
@end example

@need 1000
While in a @file{.cshrc} file, you could use the following @code{csh}
command sequence:

@example
setenv TEXINPUTS .:/home/me/mylib:
@end example

On MS-DOS/MS-Windows, you'd do this (note the use of the @samp{;}
character as directory separator, instead of @samp{:}):

@example
@group
set TEXINPUTS=.;d:/home/me/mylib;c:
@end group
@end example

@noindent
It is customary for DOS/Windows users to put such commands in the
@file{autoexec.bat} file, or in the Windows registry.

@noindent
These settings would cause @TeX{} to look for @file{\input} file first
in the current directory, indicated by the @samp{.}, then in a
hypothetical user @samp{me}'s @file{mylib} directory, and finally in
the system directories.  (A leading, trailing, or doubled @samp{:}
indicates searching the system directories at that point.)

@node Overfull hboxes
@section Overfull ``hboxes''
@cindex Overfull @samp{hboxes}
@cindex @samp{hbox}, overfull
@cindex Final output

@TeX{} is sometimes unable to typeset a line within the normal
margins.  This most often occurs when @TeX{} comes upon what it
interprets as a long word that it cannot hyphenate, such as an
electronic mail network address or a very long identifier.  When this
happens, @TeX{} prints an error message like this:

@example
Overfull @@hbox (20.76302pt too wide)
@end example

@findex hbox
@noindent
(In @TeX{}, lines are in ``horizontal boxes'', hence the term, ``hbox''.
@samp{@@hbox} is a @TeX{} primitive not used in the Texinfo language.)

@TeX{} also provides the line number in the Texinfo source file and
the text of the offending line, which is marked at all the places that
@TeX{} considered hyphenation.  @xref{Debugging with @TeX{}}, for more
information about typesetting errors.

If the Texinfo file has an overfull hbox, you can rewrite the sentence
so the overfull hbox does not occur, or you can decide to leave it.  A
small excursion into the right margin often does not matter and may not
even be noticeable.

If you have many overfull boxes and/or an antipathy to rewriting, you
can coerce @TeX{} into greatly increasing the allowable interword
spacing, thus (if you're lucky) avoiding many of the bad line breaks,
like this:

@findex \emergencystretch
@example
@@tex
\global\emergencystretch = .9\hsize
@@end tex
@end example

@noindent
(You should adjust the fraction as needed.)  This huge value for
@code{\emergencystretch} cannot be the default, since then the typeset
output would generally be of noticeably lower quality; its default
value is @samp{.15\hsize}.  @code{\hsize} is the @TeX{} dimension
containing the current line width.

@cindex Black rectangle in hardcopy
@cindex Rectangle, black in hardcopy
@cindex Box, ugly black in hardcopy
@cindex Ugly black rectangles in hardcopy
For any overfull boxes you do have, @TeX{} will print a large, ugly,
black rectangle beside the line that contains the overfull hbox unless
told otherwise.  This is so you will notice the location of the
problem if you are correcting a draft.

@findex finalout
To prevent such a monstrosity from marring your final printout, write
the following in the beginning of the Texinfo file on a line of its own,
before the @code{@@titlepage} command:

@example
@@finalout
@end example

@node @code{@@smallbook}
@section @code{@@smallbook}: Printing ``Small'' Books

@anchor{smallbook}@c old name
@findex smallbook
@cindex Small book size
@cindex Book, printing small
@cindex Page sizes for books
@cindex Size of printed book

By default, @TeX{} typesets pages for printing in an 8.5 by 11 inch
format.  However, you can direct @TeX{} to typeset a document in a 7 by
9.25 inch format that is suitable for bound books by inserting the
following command on a line by itself at the beginning of the Texinfo
file, before the title page:

@example
@@smallbook
@end example

@noindent
(Since many books are about 7 by 9.25 inches, this command might better
have been called the @code{@@regularbooksize} command, but it came to be
called the @code{@@smallbook} command by comparison to the 8.5 by 11
inch format.)

If you write the @code{@@smallbook} command between the
start-of-header and end-of-header lines, the Texinfo mode @TeX{}
region formatting command, @code{texinfo-tex-region}, will format the
region in ``small'' book size (@pxref{Start of Header}).

@xref{@code{@@small@dots{}}}, for information about commands that make
it easier to produce examples for a smaller manual.

@xref{Format with @command{texi2dvi}}, and @ref{Preparing for @TeX{}},
for other ways to format with @code{@@smallbook} that do not require
changing the source file.

@node A4 Paper
@section Printing on A4 Paper
@cindex A4 paper, printing on
@cindex A5 paper, printing on
@cindex Paper size, A4
@cindex European A4 paper
@findex afourpaper
@findex afivepaper

You can tell @TeX{} to format a document for printing on European size
A4 paper (or A5) with the @code{@@afourpaper} (or @code{@@afivepaper})
command.  Write the command on a line by itself near the beginning of
the Texinfo file, before the title page.  For example, this is how you
would write the header for this manual:

@example
@group
\input texinfo    @@c -*-texinfo-*-
@@c %**start of header
@@settitle Texinfo
@@afourpaper
@@c %**end of header
@end group
@end example

@xref{Format with @command{texi2dvi}}, and @ref{Preparing for @TeX{}},
for other ways to format for different paper sizes that do not require
changing the source file.

@findex afourlatex
@findex afourwide
You may or may not prefer the formatting that results from the command
@code{@@afourlatex}.  There's also @code{@@afourwide} for A4 paper in
wide format.

@node @code{@@pagesizes}
@section @code{@@pagesizes} [@var{width}][, @var{height}]: Custom Page Sizes
@anchor{pagesizes}@c old node name

@findex pagesizes
@cindex Custom page sizes
@cindex Page sizes, customized
@cindex Text width and height
@cindex Width of text area
@cindex Height of text area
@cindex Depth of text area

You can explicitly specify the height and (optionally) width of the main
text area on the page with the @code{@@pagesizes} command.  Write this
on a line by itself near the beginning of the Texinfo file, before the
title page.  The height comes first, then the width if desired,
separated by a comma.  Examples:

@example
@@pagesizes 200mm,150mm  @c for b5 paper
@end example
@noindent and
@example
@@pagesizes 11.5in       @c for legal paper
@end example

@cindex B5 paper, printing on
@cindex Legal paper, printing on
This would be reasonable for printing on B5-size paper.  To emphasize,
this command specifies the size of the @emph{text area}, not the size of
the paper (which is 250@dmn{mm} by 177@dmn{mm} for B5, 14@dmn{in} by
8.5@dmn{in} for legal).

@cindex Margins on page, not controllable
To make more elaborate changes, such as changing any of the page
margins, you must define a new command in @file{texinfo.tex} or
@file{texinfo.cnf}.

@xref{Format with @command{texi2dvi}}, and @ref{Preparing for @TeX{}},
for other ways to specify @code{@@pagesizes} that do not require
changing the source file.

@node Cropmarks and Magnification
@section Cropmarks and Magnification

@findex cropmarks
@cindex Cropmarks for printing
@cindex Printing cropmarks
You can (attempt to) direct @TeX{} to print cropmarks at the corners
of pages with the @code{@@cropmarks} command.  Write the
@code{@@cropmarks} command on a line by itself near the beginning of
the Texinfo file, before the title page, like this:

@example
@@cropmarks
@end example

This command is mainly for printers that typeset several pages on one
sheet of film; but you can attempt to use it to mark the corners of a
book set to 7 by 9.25 inches with the @code{@@smallbook} command.
(Printers will not produce cropmarks for regular sized output that is
printed on regular sized paper.)  Since different printing machines
work in different ways, you should explore the use of this command
with a spirit of adventure.  You may have to redefine the command in
@file{texinfo.tex}.

The @code{@@cropmarks} command is recognized and ignored in non-@TeX{}
output formats.

@findex \mag @r{(raw @TeX{} magnification)}
@cindex Magnified printing
@cindex Larger or smaller pages
You can attempt to direct @TeX{} to typeset pages larger or smaller
than usual with the @code{\mag} @TeX{} command.  Everything that is
typeset is scaled proportionally larger or smaller.  (@code{\mag}
stands for ``magnification''.)  This is @emph{not} a Texinfo
@@-command, but is a raw @TeX{} command that is prefixed with a
backslash.  You have to write this command between @code{@@tex} and
@code{@@end tex} (@pxref{Raw Formatter Commands}).

Follow the @code{\mag} command with an @samp{=} and then a number that
is 1000 times the magnification you desire.  For example, to print pages
at 1.2 normal size, write the following near the beginning of the
Texinfo file, before the title page:

@example
@group
@@tex
\global\mag=1200
@@end tex
@end group
@end example

With some printing technologies, you can print normal-sized copies that
look better than usual by giving a larger-than-normal master to your
print shop.  They do the reduction, thus effectively increasing the
resolution.

Depending on your system, DVI files prepared with a
nonstandard-@code{\mag} may not print or may print only with certain
magnifications.  Be prepared to experiment.

@node PDF Output
@section PDF Output
@cindex PDF output
@cindex Output, in PDF

@pindex pdftex
The simplest way to generate PDF output from Texinfo source is to run
the convenience script @command{texi2pdf} (or @command{pdftexi2dvi});
this executes the @command{texi2dvi} script with the @option{--pdf}
option (@pxref{Format with @command{texi2dvi}}).  If for some reason you
want to process the document by hand, you can run the @command{pdftex}
program instead of plain @command{tex}.  That is, run @samp{pdftex
foo.texi} instead of @samp{tex foo.texi}.

@dfn{PDF} stands for `Portable Document Format'. It was invented by
Adobe Systems some years ago for document interchange, based on their
PostScript language.  Related links:

@itemize
@item
GNU GV, a @uref{http://www.gnu.org/software/gv/, Ghostscript-based PDF
reader}.  (It can also preview PostScript documents.)

@item
@code{xpdf}, a freely available standalone
@uref{http://www.foolabs.com/xpdf/, PDF reader} for the X window
system.

@item
@uref{https://en.wikipedia.org/wiki/Portable_Document_Format, PDF at
Wikipedia}.

@end itemize

At present, Texinfo does not provide @samp{@@ifpdf} or @samp{@@pdf}
commands as for the other output formats, since PDF documents contain
many internal low-level offsets and cross-references that would be
hard or impossible to specify at the Texinfo source level.

PDF files require dedicated software to be displayed, unlike the plain
ASCII formats (Info, HTML) that Texinfo supports.  They also tend to
be much larger than the DVI files output by @TeX{} by default.
Nevertheless, a PDF file does define an actual typeset document in a
self-contained file, notably including all the fonts that are used, so
it has its place.

@node Obtaining @TeX{}
@section Obtaining @TeX{}
@cindex Obtaining @TeX{}
@cindex @TeX{}, how to obtain

@TeX{} is a document formatter that is used by the FSF for its
documentation.  It is the easiest way to get printed output (e.g., PDF
and PostScript) for Texinfo manuals.  TeX is freely redistributable,
and you can get it over the Internet or on physical media.  See
@url{http://tug.org/texlive}.

@c please keep that text in sync with www.gnu.org/prep/FTP

@node Generic Translator @command{texi2any}
@chapter @command{texi2any}: The Generic Translator for Texinfo

@command{texi2any} is the generic translator for Texinfo that can
produce different output formats and is highly customizable.  It
supports these formats:

@table @asis
@item Info (by default, or with @option{--info}),

@item HTML (with @option{--html}),

@item plain text (with @option{--plaintext}),

@item Docbook (with @option{--docbook}),

@item Texinfo XML (with @option{--xml}).
@end table

@command{makeinfo} is an alias for @command{texi2any}.  By default,
both @command{texi2any} and @command{makeinfo} generate Info output;
indeed, there are no differences in behavior based on the name.

Beside these default formats, command line options to
@command{texi2any} can change many aspects of the output.  Beyond
that, initialization files provide even more control over the final
output---nearly anything not specified in the Texinfo input file.
Initialization files are written in Perl, like the main program, and
anything which can be specified on the command line can also be
specified within a initialization file.

The rest of this chapter goes into the details.

@menu
* Reference Implementation::    @command{texi2any}: the reference implementation.
* Invoking @command{texi2any}::           Running the translator from a shell.
* @command{texi2any} Environment Variables::
* @command{texi2any} Printed Output::     Calling @command{texi2dvi}.
* Pointer Validation::          How to check that pointers point somewhere.
* Customization Variables::     Configuring @command{texi2any}.
* Internationalization of Document Strings:: Translating program-inserted text.
* Invoking @command{pod2texi}::           Translating Perl pod to Texinfo.
* @command{texi2html}::                   An ancestor of @command{texi2any}.
@end menu

@node Reference Implementation
@section @command{texi2any}: A Texinfo Reference Implementation

@cindex @command{texi2any}, as reference implementation
@cindex Reference implementation
@cindex Implementation, @command{texi2any} as reference

Above, we called @command{texi2any} ``the'' translator for Texinfo
instead of just ``a'' translator, even though (of course) it's
technically and legally possible for other implementations to be
written.  The reason is that alternative implementations are very
likely to have subtle, or not-so-subtle, differences in behavior, and
thus Texinfo documents would become dependent on the processor.
Therefore, it is important to have a reference implementation that
defines parts of the language not fully specified by the manual (often
intentionally so).  It is equally important to have consistent
command-line options and other behavior for all processors.

@cindex Tree representation of documents
@cindex Syntax tree representation of documents
@cindex Abstract syntax tree representation of documents
For this reason, the once-independent @command{texi2html} Perl Texinfo
processor was made compatible with the C implementation of
@command{makeinfo}, to avoid continuing with two different
implementations (@pxref{History}).  The current implementation,
@command{texi2any}, serves as the reference implementation.  It
inherited the design of customization and other features from
@command{texi2html} (for more on @command{texi2html} compatibility,
@pxref{@command{texi2html}}).  However, @code{texi2any} is a full
reimplementation: it constructs a tree-based representation of the
input document for all back-ends to work from.

@cindex Texinfo language tests
@cindex Tests, of Texinfo language
Extensive tests of the language were developed at the same time as
@command{texi2any}; we plead with anyone thinking of writing a program
to parse Texinfo input to at least make use of these tests.

@cindex Examples of using @command{texi2any}
@findex Texinfo::Parser module
The @command{texi2html} wrapper script (@pxref{@command{texi2html}})
provides a very simple example of calling @command{texi2any} from a
shell script; it's in @file{util/texi2html} in the Texinfo sources.
More consequentially, @command{texi-elements-by-size} is an example
Perl script using the @code{Texinfo::Parser} module interface; it's
also in the @file{util} source directory.  (Its functionality may also
be useful to authors; @pxref{texi-elements-by-size}.)

@cindex Future of Texinfo implementations
With the release of @command{texi2any} as the reference
implementation, development of both the C implementation of
@command{makeinfo} and @command{texi2html} has been halted.  Going
forward, we ask authors of Texinfo documents to use only
@command{texi2any}.

@node Invoking @command{texi2any}
@section Invoking @command{texi2any}/@command{makeinfo} from a Shell

@anchor{Invoking makeinfo}
@pindex makeinfo
@pindex texi2any

To process a Texinfo file, invoke @command{texi2any} or
@command{makeinfo} (the two names are synonyms for the same program;
we'll use the names interchangeably) followed by the name of the
Texinfo file.  Also select the format you want to output with the
appropriate command line option (default is Info).  Thus, to create
the Info file for Bison, type the following to the shell:

@example
texi2any --info bison.texinfo
@end example

You can specify more than one input file name; each is processed in
turn.  If an input file name is @samp{-}, standard input is read.

@anchor{@command{makeinfo} Options}
@c anchor{makeinfo options}@c prev name, but case-insensitive clash
@cindex @code{makeinfo} options
@cindex Options for @code{makeinfo}
@anchor{texi2any Options}
@cindex @code{texi2any} options
@cindex Options for @code{texi2any}

The @command{texi2any} program accepts many options.  Perhaps the
most basic are those that change the output format.  By default,
@command{texi2any} outputs Info.

Each command line option is either a long name preceded by @samp{--}
or a single letter preceded by @samp{-}.  You can use abbreviations
for the long option names as long as they are unique.

For example, you could use the following shell command to create an
Info file for @file{bison.texinfo} in which lines are filled to only
68 columns:

@example
texi2any --fill-column=68 bison.texinfo
@end example

You can write two or more options in sequence, like this:

@example
texi2any --no-split --fill-column=70 @dots{}
@end example

@noindent
(This would keep the Info file together as one possibly very long
file and would also set the fill column to 70.)

The options are (approximately in alphabetical order):

@table @code
@item --commands-in-node-names
@opindex --commands-in-node-names
This option now does nothing, but remains for compatibility.  (It used
to ensure that @@-commands in node names were expanded throughout the
document, especially @code{@@value}.  This is now done by default.)

@item --conf-dir=@var{path}
@opindex --conf-dir=@var{path}
Prepend @var{path} to the directory search list for finding
customization files that may be loaded with @option{--init-file} (see
below).  The @var{path} value can be a single directory, or a list of
several directories separated by the usual path separator character
(@samp{:} on Unix-like systems, @samp{;} on Windows). @c @xref{Loading
@c Init Files}.

@item --css-include=@var{file}
@opindex --css-include
When producing HTML, literally include the contents of @var{file},
which should contain W3C cascading style sheets specifications, in the
@samp{<style>} block of the HTML output.  If @var{file} is @samp{-},
read standard input.  @xref{HTML CSS}.

@item --css-ref=@var{url}
@opindex --css-ref
When producing HTML, add a @samp{<link>} tag to the output which
references a cascading style sheet at @var{url}.  This allows using
standalone style sheets.

@item -D @var{var}
@itemx -D '@var{var} @var{value}'
@opindex -D @var{var}
Cause the Texinfo variable @var{var} to be defined.  This is
equivalent to @code{@@set @var{var}} in the Texinfo file
(@pxref{@code{@@set @@clear @@value}}).

The argument to the option is always one word to the shell; if it
contains internal whitespace, the first word is taken as the variable
name and the remainder as the value.  For example, @code{-D 'myvar
someval'} is equivalent to @code{@@set myvar someval}.

@item --disable-encoding
@itemx --enable-encoding
@opindex --disable-encoding
@opindex --enable-encoding
By default, or with @option{--enable-encoding}, output accented and
special characters in Info and plain text output based on
@samp{@@documentencoding}.  With @option{--disable-encoding}, 7-bit
ASCII transliterations are output.  @xref{@code{@@documentencoding}},
and @ref{Inserting Accents}.

@item --docbook
@opindex --docbook
Generate Docbook output (rather than Info).

@item --document-language=@var{lang}
@opindex --document-language
Use @var{lang} to translate Texinfo keywords which end up in the
output document.  The default is the locale specified by the
@code{@@documentlanguage} command if there is one, otherwise English
(@pxref{@code{@@documentlanguage}}).

@item --dvi
@opindex --dvi
Generate a TeX DVI file using @command{texi2dvi}, rather than Info
(@pxref{@command{texi2any} Printed Output}).

@item --dvipdf
@opindex --dvipdf
Generate a PDF file using @command{texi2dvi --dvipdf}, rather than
Info (@pxref{@command{texi2any} Printed Output}).

@item --error-limit=@var{limit}
@itemx -e @var{limit}
@opindex --error-limit=@var{limit}
@opindex -e @var{limit}
Report @var{LIMIT} errors before aborting (on the assumption that
continuing would be useless); default 100.

@item --fill-column=@var{width}
@itemx -f @var{width}
@opindex --fill-column=@var{width}
@opindex -f @var{width}
Specify the maximum number of columns in a line; this is the
right-hand edge of a line.  Paragraphs that are filled will be filled
to this width.  (Filling is the process of breaking up and connecting
lines so that lines are the same length as or shorter than the number
specified as the fill column.  Lines are broken between words.) The
default value is 72.

@item --footnote-style=@var{style}
@itemx -s @var{style}
@opindex --footnote-style=@var{style}
@opindex -s @var{style}
Set the footnote style to @var{style}: either @samp{end} for the end
node style (the default) or @samp{separate} for the separate node
style.  The value set by this option overrides the value set in a
Texinfo file by a @code{@@footnotestyle} command (@pxref{Footnote
Styles}).

When the footnote style is @samp{separate}, @code{makeinfo} makes a
new node containing the footnotes found in the current node.  When the
footnote style is @samp{end}, @code{makeinfo} places the footnote
references at the end of the current node.

In HTML, when the footnote style is @samp{end}, or if the output is
not split, footnotes are put at the end of the output.  If set to
@samp{separate}, and the output is split, they are placed in a
separate file.

@item --force
@itemx -F
@opindex --force
@opindex -F
Ordinarily, if the input file has errors, the output files are not
created.  With this option, they are preserved.

@item --help
@itemx -h
@opindex --help@r{, for @command{texi2any}}
@opindex -h
Print a message with available options and basic usage, then exit
successfully.

@item --html
@opindex --html
Generate HTML output (rather than Info).  By default, the HTML output
is split into one output file per Texinfo source node, and the split
output is written into a subdirectory based on the name of the
top-level Info file.  @xref{Generating HTML}.

@item -I @var{path}
@opindex -I @var{path}
Append @var{path} to the directory search list for finding files that
are included using the @code{@@include} command.  By default,
@code{texi2any} searches only the current directory.  If @var{path} is
not given, the current directory is appended.  The @var{path} value
can be a single directory or a list of several directories separated
by the usual path separator character (@samp{:} on Unix-like systems,
@samp{;} on Windows).

@item --ifdocbook
@opindex --ifdocbook
@itemx --ifhtml
@opindex --ifhtml
@itemx --ifinfo
@opindex --ifinfo
@itemx --ifplaintext
@opindex --ifplaintext
@itemx --iftex
@opindex --iftex
@itemx --ifxml
@opindex --ifxml
For the given format, process @samp{@@if@var{format}} and
@samp{@@@var{format}} commands, and do not process
@samp{@@ifnot@var{format}}, regardless of the format being output.
For instance, if @option{--iftex} is given, then @samp{@@iftex} and
@samp{@@tex} blocks will be read, and @samp{@@ifnottex} blocks will be
ignored.

@item --info
@opindex --info
Generate Info output.  By default, if the output file contains more
than about 300,000 bytes, it is split into shorter subfiles of about
that size.  The name of the output file and any subfiles is determined
by @code{@@setfilename} (@pxref{@code{@@setfilename}}).  @xref{Tag and
Split Files}.

@item --init-file=@var{file}
@opindex --init-file=@var{file}
Load @var{file} as code to modify the behavior and output of the
generated manual.  It is customary to use the @code{.pm} or the
@code{.init} extensions for these customization files, but that is not
enforced; the @var{file} name can be anything.  The
@option{--conf-dir} option (see above) can be used to add to the list
of directories in which these customization files are searched for.
@c @xref{Loading Init Files}.

@item --internal-links=@var{file}
@opindex --internal-links=@var{file}
@cindex Internal links, of HTML
In HTML mode, output a tab-separated file containing three columns:
the internal link to an indexed item or item in the table of contents,
the name of the index (or table of contents) in which it occurs, and
the term which was indexed or entered.  The items are in the natural
sorting order for the given element.  This dump can be useful for
post-processors.

@item --macro-expand=@var{file}
@itemx -E @var{file}
@opindex --macro-expand=@var{file}
@opindex -E @var{file}
Output the Texinfo source, with all Texinfo macros expanded, to
@var{file}.  Normally, the result of macro expansion is used
internally by @code{makeinfo} and then discarded.

@item --no-headers
@opindex --no-headers
@cindex Node separators, omitting with @option{--no-headers}
@cindex Generating plain text files with @option{--no-headers}
@cindex Menus, omitting with @option{--no-headers}
Do not include menus or node separator lines in the output.

When generating Info, this is the same as using @option{--plaintext},
resulting in a simple plain text file.  Furthermore,
@code{@@setfilename} is ignored, and output is to standard output
unless overridden with @option{-o}.  (This behavior is for backward
compatibility.)

@cindex Navigation links, omitting
When generating HTML, and output is split, also output navigation
links only at the beginning of each file.  If output is not split, do
not include navigation links at the top of each node at all.
@xref{Generating HTML}.

@item --no-ifdocbook
@opindex --no-ifdocbook
@itemx --no-ifhtml
@opindex --no-ifhtml
@itemx --no-ifinfo
@opindex --no-ifinfo
@itemx --no-ifplaintext
@opindex --no-ifplaintext
@itemx --no-iftex
@opindex --no-iftex
@itemx --no-ifxml
@opindex --no-ifxml
For the given format, do not process @samp{@@if@var{format}} and
@samp{@@@var{format}} commands, and do process
@samp{@@ifnot@var{format}}, regardless of the format being output.
For instance, if @option{--no-ifhtml} is given, then @samp{@@ifhtml}
and @samp{@@html} blocks will not be read, and @samp{@@ifnothtml}
blocks will be.

@item --no-node-files
@itemx --node-files
@opindex --no-node-files
@opindex --node-files
When generating HTML, create redirection files for anchors and any
nodes not already output with the file name corresponding to the node
name (@pxref{HTML Xref Node Name Expansion}).  This makes it possible
for section- and chapter-level cross-manual references to succeed
(@pxref{HTML Xref Configuration}).

If the output is split, this is enabled by default.  If the output is
not split, @option{--node-files} enables the creation of the
redirection files, in addition to the monolithic main output file.
@option{--no-node-files} suppresses the creation of redirection files
in any case.  This option has no effect with any output format other
than HTML@.  @xref{Generating HTML}.

@item --no-number-footnotes
@opindex --no-number-footnotes
Suppress automatic footnote numbering.  By default, footnotes are
numbered sequentially within a node, i.e., the current footnote number
is reset to 1 at the start of each node.

@item --no-number-sections
@itemx --number-sections
@opindex --no-number-sections
@opindex --number-sections
With @option{--number_sections} (the default), output chapter,
section, and appendix numbers as in printed manuals.  This works only
with hierarchically-structured manuals.  You should specify
@code{--no-number-sections} if your manual is not normally structured.

@item --no-pointer-validate
@itemx --no-validate
@opindex --no-pointer-validate
@opindex --no-validate
@cindex Pointer validation, suppressing from command line
Suppress the pointer-validation phase of @code{makeinfo}---a dangerous
thing to do.  This can also be done with the @code{@@novalidate}
command (@pxref{Use @TeX{}}).  Normally, consistency checks are made
to ensure that cross-references can be resolved, etc.  @xref{Pointer
Validation}.

@item --no-warn
@opindex --no-warn
Suppress warning messages (but not error messages).

@item --output=@var{file}
@itemx -o @var{file}
@opindex --output=@var{file}
@opindex -o @var{file}
Specify that the output should be directed to @var{file}.  This
overrides any file name specified in a @code{@@setfilename} command
found in the Texinfo source.  If neither @code{@@setfilename} nor this
option are specified, the input file name is used to determine the
output name.  @xref{@code{@@setfilename}}.

If @var{file} is @samp{-}, output goes to standard output and
@samp{--no-split} is implied.

If @var{file} is a directory or ends with a @samp{/} the usual rules
are used to determine the output file name (namely, use
@code{@@setfilename} or the input file name) but the files are written
to the @var{file} directory.  For example, @samp{makeinfo -o bar/
foo.texi}, with or without @option{--no-split}, will write
@file{bar/foo.info}, and possibly other files, under @file{bar/}.

When generating HTML and output is split, @var{file} is used as the
name for the directory into which all files are written.  For example,
@samp{makeinfo -o bar --html foo.texi} will write
@file{bar/index.html}, among other files.

@item --output-indent=@var{val}
@opindex --outputindent
This option now does nothing, but remains for compatibility.  (It used
to alter indentation in XML/Docbook output.)

@item -P @var{path}
@opindex -P @var{path}
Prepend @var{path} to the directory search list for @code{@@include}.
If @var{path} is not given, the current directory is prepended.  See
@samp{-I} above.

@item --paragraph-indent=@var{indent}
@itemx -p @var{indent}
@opindex --paragraph-indent=@var{indent}
@opindex -p @var{indent}
Set the paragraph indentation style to @var{indent}.  The value set by
this option overrides the value set in a Texinfo file by an
@code{@@paragraphindent} command (@pxref{@code{@@paragraphindent}}).
The value of @var{indent} is interpreted as follows:

@table @asis
@item @samp{asis}
Preserve any existing indentation (or lack thereof) at the beginnings
of paragraphs.

@item @samp{0} or @samp{none}
Delete any existing indentation.

@item @var{num}
Indent each paragraph by @var{num} spaces.
@end table

The default is to indent by two spaces, except for paragraphs
following a section heading, which are not indented.

@item --pdf
@opindex --pdf
Generate a PDF file using @command{texi2dvi --pdf}, rather than Info
(@pxref{@command{texi2any} Printed Output}).

@item --plaintext
@opindex --plaintext
@cindex Plain text output with @option{--plaintext}
@cindex ASCII text output with @option{--plaintext}
@cindex Generating plain text files with @option{--plaintext}
@cindex Node separators, omitting with @option{--plaintext}
@cindex Menus, omitting with @option{--plaintext}
@cindex @file{INSTALL} file, generating
Output a plain text file (rather than Info): do not include menus or
node separator lines in the output.  This results in a straightforward
plain text file that you can (for example) send in email without
complications, or include in a distribution (for example, an
@file{INSTALL} file).

With this option, @code{@@setfilename} is ignored and the output goes
to standard output by default; this can be overridden with @option{-o}.

@item --ps
@opindex --ps
Generate a PostScript file using @command{texi2dvi --ps}, rather than
Info (@pxref{@command{texi2any} Printed Output}).

@item --set-customization-variable @var{var}=@var{value}
@itemx -c @var{var}=@var{value}
@opindex --set-customization-variable @var{var}=@var{value}
@opindex -c @var{var}=@var{value}
Set the customization variable @var{var} to @var{value}.  The @code{=}
is optional, but both @var{var} and @var{value} must be quoted to the
shell as necessary so the result is a single word.  Many aspects of
@command{texi2any} behavior and output may be controlled by
customization variables, beyond what can be set in the document by
@@-commands and with other command line switches.  @xref{Customization
Variables}.

@item --split=@var{how}
@itemx --no-split
@opindex --split=@var{how}
@opindex --no-split
@cindex Splitting of output files
@cindex Output file splitting
@anchor{Splitting Output}
@c
When generating Info, by default large output files are split into
smaller subfiles, of approximately 300k bytes.  When generating HTML,
by default each output file contains one node (@pxref{Generating
HTML}).  @option{--no-split} suppresses this splitting of the output.

Alternatively, @option{--split=@var{how}} may be used to specify at
which level the HTML output should be split.  The possible values for
@var{how} are:

@table @samp
@item chapter
The output is split at @code{@@chapter} and other sectioning
@@-commands at this level (@code{@@appendix}, etc.).

@item section
The output is split at @code{@@section} and similar.

@item node
The output is split at every node.  This is the default.
@end table

Plain text output can be split similarly to HTML@.  This may be useful
for extracting sections from a Texinfo document and making them
available as separate files.

@item --split-size=@var{num}
@opindex --split-size=@var{num}
Keep Info files to at most @var{num} characters if possible; default
is 300,000.  (However, a single node will never be split across Info
files.)

@item --transliterate-file-names
@opindex --transliterate-file-names
Enable transliteration of 8-bit characters in node names for the
purpose of file name creation.  @xref{HTML Xref 8-bit Character Expansion}.

@item -U @var{var}
Cause @var{var} to be undefined.  This is equivalent to @code{@@clear
@var{var}} in the Texinfo file (@pxref{@code{@@set @@clear @@value}}).

@item --verbose
@opindex --verbose
Cause @code{makeinfo} to display messages saying what it is doing.
Normally, @code{makeinfo} only outputs messages if there are errors or
warnings.

@item --version
@itemx -V
@opindex --version@r{, for @command{texi2any}}
@opindex -V
Print the version number, then exit successfully.

@item --Xopt @var{str}
@opindex --Xopt @var{str}
Pass @var{str} (a single shell word) to @command{texi2dvi}; may be
repeated (@pxref{@command{texi2any} Printed Output}).

@item --xml
@opindex --xml
Generate Texinfo XML output (rather than Info).

@end table

@node @command{texi2any} Environment Variables
@section Environment Variables Recognized by @command{texi2any}

@vindex TEXINFO_OUTPUT_FORMAT
@cindex Environment variable @code{TEXINFO_OUTPUT_FORMAT}
@command{makeinfo} also reads the environment variable
@env{TEXINFO_OUTPUT_FORMAT} to determine the output format, if not
overridden by a command line option.  The value should be one of:

@example
docbook  dvi  dvipdf  html  info  pdf  plaintext  ps  xml
@end example

If not set or otherwise specified, Info output is the default.

The customization variable of the same name is also read; if set, that
overrides an environment variable setting, but not a command-line
option.  @xref{Customization Variables and Options}.

@vindex TEXINFO_XS
@cindex Perl extension modules (XS)
You can control @command{texi2any}'s use of Perl extension modules
by setting the @env{TEXINFO_XS} environment variable.  These modules
are compiled native code that the interpreted Perl code can use.
Ideally, these extension modules should just work, and the only noticable
difference they should make is that @command{texi2any} finishes running
sooner.  However, you can use this environment variable for the purposes
of troubleshooting: for example, if you have problems with the output of
@command{texi2any} varying depending on whether the extension modules are
in use.

The following values of @env{TEXINFO_XS} are recognized by
@command{texi2any}:

@table @samp
@item default
The default behavior.  Try to load extension modules, and silently fall
back to the interpreted Perl implementations if this fails.

@item warn
Try to load extension modules, and if this fails, give a warning message
before falling back to the interpreted Perl implementations.

@item debug
Try to load extension modules, printing many messages while doing so.

@item omit
Do not use extension modules.

@end table

@node @command{texi2any} Printed Output
@section @command{texi2any} Printed Output

@cindex Printed output, through @command{texi2any}
@cindex Output, printed through @command{texi2any}

To justify the name Texinfo-to-@emph{any}, @command{texi2any} has
basic support for creating printed output in the various formats:
@TeX{} DVI, PDF, and PostScript.  This is done via the simple method
of executing the @command{texi2dvi} program when those output formats
are requested, after checking the validity of the input to give users
the benefit of @command{texi2any}'s error checking.  If you don't want
such error checking, perhaps because your manual plays advanced @TeX{}
tricks together with @file{texinfo.tex}, just invoke
@command{texi2dvi} directly.

The output format options for this are @option{--dvi},
@option{--dvipdf}, @option{--pdf}, and @option{--ps}.  @xref{Format
with @command{texi2dvi}}, for more details on these options and general
@command{texi2dvi} operation.  In addition, the @option{--verbose},
@option{--silent}, and @option{--quiet} options are passed on if
specified; the @option{-I} and @option{-o} options are likewise passed
on with their arguments, and @option{--debug} without its argument.

The only option remaining that is related to the @command{texi2dvi}
invocation is @option{--Xopt}.  Here, just the argument is passed on
and multiple @option{--Xopt} options accumulate.  This provides a way
to construct an arbitrary command line for @command{texi2dvi}.  For
example, running

@example
texi2any --Xopt -t --Xopt @@a4paper --pdf foo.texi
@end example

@noindent is equivalent to running

@example
texi2dvi -t @@a4paper --pdf foo.texi
@end example

@noindent except for the validity check.

Although one might wish that other options to @command{texi2any} would
take effect, they don't.  For example, running @samp{texi2any
--no-number-sections --dvi foo.texi} still results in a DVI file with
numbered sections.  (Perhaps this could be improved in the future, if
requests are received.)

The actual name of the command that is invoked is specified by the
@code{TEXI2DVI} customization variable (@pxref{Other Customization
Variables}).  As you might guess, the default is @samp{texi2dvi}.

@command{texi2any} itself does not generate any normal output when it
invokes @command{texi2dvi}, only diagnostic messages.

@node Pointer Validation
@section Pointer Validation
@cindex Pointer validation with @code{makeinfo}
@cindex Validation of pointers

If you do not suppress pointer validation with the
@samp{--no-validate} option or the @code{@@novalidate} command in the
source file (@pxref{Use @TeX{}}), @code{makeinfo} will check the
validity of the Texinfo file.

Most validation checks are different depending on whether node
pointers are explicitly or implicitly determined.  With explicit node
pointers, here is the list of what is checked:

@enumerate
@item
If a `Next', `Previous', or `Up' node reference is a reference to a
node in the current file and is not an external reference such as to
@file{(dir)}, then the referenced node must exist.

@item
Every node except the `Top' node must have an `Up' pointer.

@item
The node referenced by an `Up' pointer must itself reference the
current node through a menu item, unless the node referenced by `Up'
has the form @samp{(@var{file})}.
@end enumerate

With implicit node pointers, the above error cannot occur, as such.
(Which is a major reason why we recommend using this feature of
@code{makeinfo}, and not specifying any node pointers yourself.)

Instead, @code{makeinfo} checks that the tree constructed from the
document's menus matches the tree constructed from the sectioning
commands.  For example, if a chapter-level menu mentions nodes
@var{n1} and @var{n2}, in that order, nodes @var{n1} and @var{n2} must
be associated with @code{@@section} commands in the chapter.

Finally, with both explicit and implicit node pointers,
@code{makeinfo} checks that every node except the `Top' node is
referenced in a menu.

@node Customization Variables
@section Customization Variables

@quotation Warning
These customization variable names and meanings may change in any
Texinfo release.  We always try to avoid incompatible changes, but we
cannot absolutely promise, since needs change over time.
@end quotation

Many aspects of the behavior and output of @command{texi2any} may be
modified by modifying so-called @dfn{customization variables}.  These
fall into a few general categories:

@itemize @bullet
@item
Those associated with @@-commands; for example,
@code{@@documentlanguage}.

@item
Those associated with command-line options; for example, the
customization variable @code{SPLIT} is associated with the
@option{--split} command-line option, and @code{TEXINFO_OUTPUT_FORMAT}
allows specifying the output format.

@item
Those associated with customizing the HTML output.

@item
Other ad hoc variables.
@end itemize

Customization variables may set on the command line using
@code{--set-customization-variable '@var{var} @var{value}'} (quoting
the variable/value pair to the shell) or
@code{--set-customization-variable @var{var}=@var{value}} (using
@code{=}).  A special @var{value} is @samp{undef}, which sets the
variable to this special ``undefined'' Perl value.

The sections below give the details for each of these.

@menu
* Commands: Customization Variables for @@-Commands.
* Options:  Customization Variables and Options.
* HTML:     HTML Customization Variables.
* Other:    Other Customization Variables.
@end menu

@node Customization Variables for @@-Commands
@subsection Customization Variables for @@-Commands

@cindex Customization variables for @@-commands
@cindex @@-commands, customization variables for

Each of the following @@-commands has an associated customization
variable with the same name (minus the leading @code{@@}):

@smallexample
@@allowcodebreaks @@clickstyle @@codequotebacktick
@@codequoteundirected @@contents @@deftypefnnewline
@@documentdescription @@documentencoding @@documentlanguage
@@evenfooting   @@evenfootingmarks
@@evenheading   @@evenheadingmarks
@@everyfooting  @@everyfootingmarks
@@everyheading  @@everyheadingmarks
@@exampleindent @@firstparagraphindent
@@fonttextsize  @@footnotestyle @@frenchspacing @@headings
@@kbdinputstyle @@novalidate
@@oddfooting    @@oddfootingmarks
@@oddheading    @@oddheadingmarks
@@pagesizes     @@paragraphindent
@@setchapternewpage  @@setfilename
@@shortcontents  @@urefbreakstyle
@@validatemenus  @@xrefautomaticsectiontitle
@end smallexample

Setting such a customization variable to a value @samp{foo} is similar
to executing @code{@@@var{cmd} foo}.  It is not exactly the same,
though, since any side effects of parsing the Texinfo source are not
redone.  Also, some variables do not take Texinfo code when generating
particular formats, but an argument that is already formatted.  This
is the case, for example, for HTML for @code{documentdescription}.

@node Customization Variables and Options
@subsection Customization Variables and Options

@cindex Customization variables for options
@cindex Options, customization variables for

The following table gives the customization variables associated with
some command line options.  @xref{Invoking @command{texi2any}}, for the
meaning of the options.

@multitable @columnfractions 0.5 0.5
@headitem Option @tab Variable
@item
@vindex ENABLE_ENCODING
@option{--enable-encoding}   @tab @code{ENABLE_ENCODING}
@item
@option{--document-language} @tab @code{documentlanguage}
@item
@vindex ERROR_LIMIT
@option{--error-limit}       @tab @code{ERROR_LIMIT}
@item
@vindex FILLCOLUMN
@option{--fill-column}       @tab @code{FILLCOLUMN}
@vindex footnotestyle
@item
@option{--footnote-style}    @tab @code{footnotestyle}
@item
@vindex FORCE
@option{--force}             @tab @code{FORCE}
@vindex INTERNAL_LINKS
@item
@option{--internal-links}    @tab @code{INTERNAL_LINKS}
@item
@vindex MACRO_EXPAND
@option{--macro-expand}      @tab @code{MACRO_EXPAND}
@item
@option{--headers}           @tab @code{HEADERS}, @code{SHOW_MENU}
@item
@vindex NO_WARN
@option{--no-warn}           @tab @code{NO_WARN}
@item
@vindex novalidate
@option{--no-validate}       @tab @code{novalidate}
@item
@vindex NUMBER_FOOTNOTES
@option{--number-footnotes}  @tab @code{NUMBER_FOOTNOTES}
@item
@vindex NUMBER_SECTIONS
@option{--number-sections}   @tab @code{NUMBER_SECTIONS}
@item
@vindex NODE_FILES
@option{--node-files}        @tab @code{NODE_FILES}
@item
@vindex OUT
@vindex OUTFILE
@vindex SUBDIR
@option{--output}            @tab @code{OUT}, @code{OUTFILE},
                                        @code{SUBDIR}
@item
@vindex paragraphindent
@option{--paragraph-indent}  @tab @code{paragraphindent}
@item
@vindex SILENT
@option{--silent}            @tab @code{SILENT}
@item
@vindex SPLIT
@option{--split}             @tab @code{SPLIT}
@item
@vindex SPLIT_SIZE
@option{--split-size}        @tab @code{SPLIT_SIZE}
@item
@vindex TRANSLITERATE_FILE_NAMES
@option{--transliterate-file-names} @tab @code{TRANSLITERATE_FILE_NAMES}
@item
@vindex VERBOSE
@option{--verbose}           @tab @code{VERBOSE}
@end multitable

Setting such a customization variable to a value @samp{foo} is
essentially the same as specifying the @code{--@var{opt}=foo} if the
option takes an argument, or @code{--@var{opt}} if not.

@vindex TEXINFO_OUTPUT_FORMAT
In addition, the customization variable @code{TEXINFO_OUTPUT_FORMAT}
allows specifying what @code{makeinfo} outputs, either one of the usual
output formats that can be specified with options, or various other
forms:

@ftable @samp
@item docbook
@itemx dvi
@itemx dvipdf
@itemx html
@itemx info
@itemx pdf
@itemx plaintext
@itemx ps
@itemx xml
These correspond to the command-line options (and
@code{TEXINFO_OUTPUT_FORMAT} environment variable values) of the same
name.  @xref{Invoking @command{texi2any}}.

@item debugtree
@cindex tree representation, for debugging
@cindex debugging document, with tree representation
Instead of generating a regular output format, output a text representation
of the tree obtained by parsing the input texinfo document.

@item parse
Do only Texinfo source parsing; there is no output.

@item plaintexinfo
Output the Texinfo source with all the macros, @code{@@include} and
@code{@@value@{@}} expanded.  This is similar to setting
@option{--macro-expand}, but instead of being output in addition to
the normal conversion, output of Texinfo is the main output.

@item rawtext
@cindex raw text output
Output raw text, with minimal formatting.  For example, footnotes are
ignored and there is no paragraph filling.  This is used by the parser
for file names and copyright text in HTML comments, for example.

@item structure
Do only Texinfo source parsing and determination of the document
structure; there is no output.

@item texinfosxml
@cindex SXML output
@cindex S-expressions, output format
Output the document in TexinfoSXML representation, a syntax for
writing XML data using Lisp S-expressions.

@item textcontent
@cindex spell checking
@cindex word counting
@pindex detexinfo
@cindex stripping Texinfo commands
Output the text content only, stripped of commands; this is useful for
spell checking or word counting, for example.  The trivial
@code{detexinfo} script setting this is in the @file{util} directory
of the Texinfo source as an example.  It's one line:

@example
exec texi2any -c TEXINPUT_OUTPUT_FORMAT=textcontent "$@@"
@end example
@end ftable

@node HTML Customization Variables
@subsection HTML Customization Variables

This table gives the customization variables which apply to HTML
output only.  A few other customization variable apply to both HTML
and other output formats; those are given in the next section.

@vtable @code
@item AVOID_MENU_REDUNDANCY
For HTML@.  If set, and the menu entry and menu description are the
same, then do not print the menu description; default false.

@item AFTER_BODY_OPEN
For HTML@.  If set, the corresponding text will appear at the
beginning of each HTML file; default unset.

@item AFTER_ABOUT
For HTML, when an About-element is output.  If set, the corresponding
text will appear at the end of the About element; default unset.

@item AFTER_OVERVIEW
@itemx AFTER_TOC_LINES
For HTML@.  If set, the corresponding text is output after the short
table of contents for @code{AFTER_OVERVIEW} and after the table of
contents for @code{AFTER_TOC_LINES}; otherwise, a default string is
used.  At the time of writing, a @code{</div>} element is closed.

In general, you should set @code{BEFORE_OVERVIEW} if
@code{AFTER_OVERVIEW} is set, and you should set
@code{BEFORE_TOC_LINES} if @code{AFTER_TOC_LINES} is set.

@item BASEFILENAME_LENGTH
For HTML@.  The maximum length of the base filenames; default 245.
Changing this would make cross-manual references to such long node
names invalid (@pxref{HTML Xref Link Basics}).

@item BEFORE_OVERVIEW
@itemx BEFORE_TOC_LINES
For HTML@.  If set, the corresponding text is output before the short
table of contents for @code{BEFORE_OVERVIEW} and before the table of
contents for @code{BEFORE_TOC_LINES}, otherwise a default string is
used.  At the time of writing, a @code{<div ...>} element is opened.

In general you should set @code{AFTER_OVERVIEW} if
@code{BEFORE_OVERVIEW} is set, and you should set
@code{AFTER_TOC_LINES} if @code{BEFORE_TOC_LINES} is set.

@item BIG_RULE
For HTML@.  Rule used after and before the top element and before
special elements, but not for footers and headers; default
@code{<hr>}.

@item BODYTEXT
@cindex @code{<body>} text, customizing
@opindex lang@r{, HTML attribute}
For HTML, the text appearing in @code{<body>}.  By default, sets the
HTML @code{lang} attribute to the document language
(@pxref{@code{@@documentlanguage}}).

@item CASE_INSENSITIVE_FILENAMES
For HTML@.  Construct output file names as if the filesystem were case
insensitive (@pxref{HTML Splitting}); default false.

@item CHAPTER_HEADER_LEVEL
For HTML@.  Header formatting level used for chapter level sectioning
commands; default @samp{2}.

@item CHECK_HTMLXREF
For HTML@.  Check that manuals which are the target of external
cross-references (@pxref{Four and Five Arguments}) are present in
@file{htmlxref.cnf} (@pxref{HTML Xref Configuration}); default false.

@item COMPLEX_FORMAT_IN_TABLE
For HTML@.  If set, use tables for indentation of complex formats; default
false.

@item CSS_LINES
For HTML@.  CSS output, automatically determined by default (@pxref{HTML CSS}).

@item DATE_IN_HEADER
For HTML@.  Put the document generation date in the header; off by default.

@item DEF_TABLE
For HTML@.  If set, a @code{<table>} construction for @code{@@deffn}
and similar @@-commands is used (looking more like the @TeX{} output),
instead of definition lists; default false.

@item DEFAULT_RULE
For HTML@.  Rule used between element, except before and after the
top element, and before special elements, and for footers and headers;
default @code{<hr>}.

@item DO_ABOUT
For HTML@.  If set to 0 never do an About special element;
if set to 1 always do an About special element;
default 0.
@c @xref{Output Elements Defined}.

@item EXTERNAL_DIR
For HTML@.  Base directory for external manuals; default none.  It is
better to use the general external cross-reference mechanism
(@pxref{HTML Xref Configuration}) than this variable.

@item EXTRA_HEAD
For HTML@.  Additional text appearing within @code{<head>}; default unset.

@item FOOTNOTE_END_HEADER_LEVEL
For HTML@.  Header formatting level used for the footnotes header with
the `end' footnotestyle; default @samp{4}.  @xref{Footnote Styles}.

@item FOOTNOTE_SEPARATE_HEADER_LEVEL
For HTML@.  Header formatting level used for the footnotes header with
the `separate' footnotestyle; default @samp{4}.  @xref{Footnote
Styles}.

@item FRAMES
For HTML@.  If set, a file describing the frame layout is generated,
together with a file with the short table of contents; default false.

@item FRAMESET_DOCTYPE
For HTML@.  Same as DOCTYPE, but for the file containing the frame
description.

@item HEADER_IN_TABLE
For HTML@.  Use tables for header formatting rather than a simple
@code{<div>} element; default false.

@item ICONS
For HTML@.  Use icons for the navigation panel; default false.

@item IMAGE_LINK_PREFIX
For HTML@.  If set, the associated value is prepended to the image file
links; default unset.

@item INLINE_CONTENTS
For HTML@.  If set, output the contents where the @code{@@contents} and
similar @@-commands are located; default true.  This is ignored if
@code{@@set*contentsaftertitlepage} is set (@pxref{Contents}).

@item INLINE_CSS_STYLE
For HTML@.  Put CSS directly in HTML elements rather than at the
beginning of the output; default false.

@item KEEP_TOP_EXTERNAL_REF
For HTML@.  If set, do not ignore @samp{Top} as the first
argument for an external ref to a manual, as is done by default.
@xref{Referring to a Manual as a Whole}.

@item L2H
For HTML@.  If set, @command{latex2html} is used to convert @code{@@math}
and @code{@@tex} sections; default false.  Best used with @option{--iftex}.

@item L2H_CLEAN
(Relevant only if @code{L2H} is set.)  If set, the intermediate files
generated in relation with @command{latex2html} are removed; default
true.

@item L2H_FILE
(Relevant only if @code{L2H} is set.)  If set, the given file is used
as @command{latex2html}'s init file; default unset.

@item L2H_HTML_VERSION
(Relevant only if @code{L2H} is set.)  The HTML version used in the
@command{latex2html} call; default unset.

@item L2H_L2H
(Relevant only if @code{L2H} is set.)  The program invoked as
@command{latex2html}; default is @code{latex2html}.

@item L2H_SKIP
(Relevant only if @code{L2H} is set.)  If set to a true value, the
actual call to @command{latex2html} is skipped; previously generated
content is reused instead.  If set to 0, the cache is not used at all.
If set to @samp{undef}, the cache is used for as many @TeX{} fragments as
possible and for any remaining the command is run.  The default is
@samp{undef}.

@item L2H_TMP
(Relevant only if @code{L2H} is set.)  Set the directory used for
temporary files.  None of the file name components in this directory
name may start with @samp{.}; otherwise, @command{latex2html} will
fail (because of @command{dvips}).  The default is the empty string,
which means the current directory.

@item MAX_HEADER_LEVEL
For HTML@.  Maximum header formatting level used (higher header
formatting level numbers correspond to lower sectioning levels);
default @samp{4}.

@item MENU_SYMBOL
For HTML@.  Symbol used in front of menu entries when node names are used
for menu entries formatting; default @samp{•}.

@item MONOLITHIC
For HTML@.  Output only one file including the table of contents.  Set
by default, but only relevant when the output is not split.

@item NO_CSS
For HTML@.  Do not use CSS; default false.  @xref{HTML CSS}.

@item NODE_FILE_EXTENSION
For HTML@.  Extension for node files if @code{NODE_FILENAMES} is set;
default @samp{html}.

@item PRE_ABOUT
For HTML, when an About element is output.  If set to a text string,
this text will appear at the beginning of the About element.  If set
to a reference on a subroutine, the result of the subroutine call will
appear at the beginning of the About element.  If not set (the
default), default text is used.

@item PRE_BODY_CLOSE
For HTML@.  If set, the given text will appear at the footer of each
HTML file; default unset.

@item PROGRAM_NAME_IN_FOOTER
For HTML@.  If set, output the program name and miscellaneous related
information in the page footers; default false.

@item SHORTEXTN
For HTML@.  If set, use @samp{.htm} as extension; default false.

@item SHOW_TITLE
For HTML@.  If set, output the title at the beginning of the document;
default true.

@item SIMPLE_MENU
For HTML@.  If set, use a simple preformatted style for the menu,
instead of breaking down the different parts of the menu; default false.
@xref{Menu Parts}.

@item TOC_LINKS
For HTML@.  If set, links from headings to toc entries are created;
default false.

@item TOP_FILE
This file name may be used for the top-level file.  The extension is
set appropriately, if necessary.  This is used to override the default,
and is, in general, only taken into account when output is split, and
for HTML@.

@item TOP_NODE_FILE
For HTML@.  File name used for the Top node, if @code{NODE_FILENAMES}
is set; default is @code{index}.

@item TOP_NODE_FILE_TARGET
For HTML@.  File name used for the Top node in cross-references;
default is @code{index}.

@item TOP_NODE_UP_URL
For HTML@.  A url used for @code{(dir)} references; the default is
@code{undef}, meaning that the normal rules apply, typically leading
to a link to @samp{dir.html} from an implicit or explicit reference to
@samp{(dir)} (@pxref{HTML Xref}).  For more about the Top node
pointers, @pxref{First Node}.  For overriding the Up pointer in other
formats, see @code{TOP_NODE_UP} in @ref{Other Customization
Variables}.

@item USE_ACCESSKEY
@cindex @code{accesskey}, customization variable for
For HTML@.  Use @code{accesskey} in cross-references; default true.

@item USE_ISO
For HTML@.  Use entities for doubled single-quote characters
(@pxref{Inserting Quotation Marks}), and @samp{---} and @samp{--}
(@pxref{Conventions}); default true.

@item USE_LINKS
@cindex @code{<link>} HTML tag, in @code{<head>}
@cindex @code{<head>} HTML tag, and @code{<link>}
For HTML@.  Generate @code{<link>} elements in the HTML @code{<head>}
output; default true.

@item USE_REL_REV
For HTML@.  Use @code{rel} in cross-references; default true.

@item VERTICAL_HEAD_NAVIGATION
For HTML@.  If set, a vertical navigation panel is used; default false.

@item WORDS_IN_PAGE
@cindex Navigation panel, bottom of page
@cindex Navigation footer
For HTML, with output split at nodes.  Specifies the approximate
minimum page length at which a navigation panel is placed at the
bottom of a page.  To avoid ever having the navigation buttons at the
bottom of a page, set this to a sufficiently large number.  The
default is 300.

@item XREF_USE_FLOAT_LABEL
For HTML@.  If set, for the float name in cross-references, use the
float label instead of the type followed by the float number
(@pxref{@code{@@float}}).  The default is off.

@item XREF_USE_NODE_NAME_ARG
For HTML@.  Only relevant for cross-reference commands with no cross
reference name (second argument).  If set to@tie{}1, use the node name
(first) argument in cross-reference @@-commands for the text displayed
as the hyperlink.  If set to@tie{}0, use the node name if
@code{USE_NODES} is set, otherwise the section name.  If set to
@samp{undef}, use the first argument in preformatted environments,
otherwise use the node name or section name depending on
@code{USE_NODES}.  The default is @samp{undef}.

@end vtable

@node Other Customization Variables
@subsection Other Customization Variables

This table gives the remaining customization variables, which apply to
multiple formats, or affect global behavior, or otherwise don't fit
into the categories of the previous sections.

@vtable @code
@item CLOSE_QUOTE_SYMBOL
When a closing quote is needed, use this character; default @code{’}
in HTML, @code{’} in Docbook.  The default for Info is the same
as @code{OPEN_QUOTE_SYMBOL} (see below).

@c @item COMPLETE_IMAGE_PATHS
@c If set, the image files are computed to be relative from the document
@c directory to the source manual directory, and then to the image.

@item CPP_LINE_DIRECTIVES
Recognize @code{#line} directives in a ``preprocessing'' pass
(@pxref{External Macro Processors}); on by default.

@item DEBUG
If set, debugging output is generated; default is off (zero).
@c The integer value specifies what kinds of debugging output are
@c generated.  It is a bitmask.  Setting it to 255 ensures having all
@c available debugging output.

@item DOCTYPE
@vindex SystemLiteral
For Docbook, HTML, XML@.  Specifies the @code{SystemLiteral}, the
entity's system identifier.  This is a URI which may be used to
retrieve the entity, and identifies the canonical DTD for the
document.  The default value is different for each of HTML, Docbook
and Texinfo@tie{}XML.

@item DUMP_TEXI
For debugging.  If set, no conversion is done, only parsing and macro
expansion.  If the option @option{--macro-expand} is set, the Texinfo
source is also expanded to the corresponding file.  Default false.

@item DUMP_TREE
For debugging.  If set, the tree constructed upon parsing a Texinfo
document is output to standard error; default false.

@item ENABLE_ENCODING_USE_ENTITY
For HTML, XML@.  If @option{--enable-encoding} is set, and there is an
entity corresponding with the letter or the symbol being output,
prefer the entity.  Set by default for HTML, but not XML.

@item EXTERNAL_CROSSREF_SPLIT
For cross-references to other manuals, this determines if the other
manual is considered to be split or monolithic.  By default, it is set
based on the value of @code{SPLIT}.  @xref{HTML Xref}, and @pxref{HTML
Xref Configuration}.

@item EXTENSION
The extension added to the output file name.  The default is different
for each output format.

@item FIX_TEXINFO
For ``plain Texinfo'' (see the @code{PLAINTEXINFO} item).  If set to
false, the resulting Texinfo does not have all errors corrected, such
as missing @samp{@@end}; default true.  This variable is only
relevant when expanding Texinfo; other converters always try to
output something sane even if the input is erroneous.

@c @item IDX_SUMMARY
@c If set, for each @code{@@printindex} a file named
@c @file{@var{docname}_@var{idxname}.idx} is created, containing lines of
@c the form:
@c
@c @example
@c @var{key} @var{reference}
@c @end example
@c
@c @noindent sorted alphabetically (case matters).

@item IGNORE_BEFORE_SETFILENAME
If set, begin outputting at @code{@@setfilename}, if
@code{@@setfilename} is present; default true.

@item IGNORE_SPACE_AFTER_BRACED_COMMAND_NAME
If set, spaces are ignored after an @@-command that takes braces.
Default true, matching the @TeX{} behavior.

@item INDEX_ENTRY_COLON
Symbol used between the index entry and the associated node or section;
default @samp{:}.

@item INDEX_SPECIAL_CHARS_WARNING
If set, warn about @samp{:} in index entry, as it leads to invalid entries in
index menus in output Info files.  For Info and plaintext only.

@anchor{INFO_SPECIAL_CHARS_QUOTE}
@item INFO_SPECIAL_CHARS_QUOTE
If set, whenever there are problematic characters for Info output in
places such as node names or menu items, surround the part of the
construct where they appear with quoting characters, as described in
@ref{Info Format Specification}.  @xref{Node Line Requirements}.

@item INFO_SPECIAL_CHARS_WARNING
If set, warn about problematic constructs for Info output (such as the
string @samp{::}) in node names, menu items, and cross-references;
default true.  Do not warn about index entries, since parsing problems
there don't prevent navigation; readers can still relatively easily
find their way to the node in question.

@item INLINE_INSERTCOPYING
If set, @code{@@insertcopying} is replaced by the @code{@@copying}
content (@pxref{@code{@@copying}}) as if @code{@@insertcopying} were a
user-defined macro; default false.

@item INPUT_ENCODING_NAME
Normalized encoding name suitable for output.  Should be a usable
charset name in HTML, typically one of the preferred IANA encoding
names.  You should not need to use this variable, since it is set by
@code{@@documentencoding} (@pxref{@code{@@documentencoding}}).

@item INPUT_PERL_ENCODING
Perl encoding used to process the Texinfo source.  You should not need
to use that variable, since it is set by @code{@@documentencoding}
(@pxref{@code{@@documentencoding}}).

@item MAX_MACRO_CALL_NESTING
The maximal number of recursive calls of @@-commands defined through
@code{@@rmacro}; default 100000.  The purpose of this variable is to
avoid infinite recursions.

@item MENU_ENTRY_COLON
Symbol used between the menu entry and the description; default
@samp{:}.

@item NO_USE_SETFILENAME
If set, do not use @code{@@setfilename} to set the document name;
instead, base the output document name only on the input file name.
The default is false.

@item NODE_FILENAMES
If set, node names are used to construct file names.  By default, it
is set if the output is split by node, or if @code{NODE_FILES} is set
and the output is split in any way.

@item NODE_NAME_IN_INDEX
If set, use node names in index entries, otherwise prefer section names;
default true.

@item NODE_NAME_IN_MENU
If set, use node names in menu entries, otherwise prefer section names;
default true.

@item OPEN_QUOTE_SYMBOL
When an opening quote is needed, e.g., for @samp{@@samp} output, use
the specified character; default @code{‘} for HTML,
@code{‘} for Docbook.  For Info, the default depends on the
enabled document encoding (@pxref{@code{@@documentencoding}}); if no
document encoding is set, or the encoding is US-ASCII, etc., @samp{'}
is used.  This character usually appears as an undirected single quote
on modern systems.  If the document encoding is Unicode, the Info
output uses a Unicode left quote.

@item OUTPUT_ENCODING_NAME
Normalized encoding name used for output files.  Should be a usable
charset name in HTML, typically one of the preferred IANA encoding
names.  By default, if an input encoding is set (typically through
@code{@@documentencoding} or @code{INPUT_ENCODING_NAME}), this
information is used to set the output encoding name.  If no input
encoding is specified, the default output encoding name may be set by
the output format.  In particular, the XML-based formats use
@code{utf-8} for @code{OUTPUT_ENCODING_NAME} if the encoding is not
otherwise specified.  @xref{@code{@@documentencoding}}.

@item OVERVIEW_LINK_TO_TOC
If set, the cross-references in the Overview link to the corresponding
Table of Contents entries; default true.

@item PACKAGE
@itemx PACKAGE_VERSION
@itemx PACKAGE_AND_VERSION
@itemx PACKAGE_URL
@itemx PACKAGE_NAME
The implementation's short package name, package version, package name
and version concatenated, package url, and full package name,
respectively.  By default, these variables are all set through
Autoconf, Automake, and @code{configure}.

@item PREFIX
The output file prefix, which is prepended to some output file names.
By default it is set by @code{@@setfilename} or from the input file
(@pxref{@code{@@setfilename}}).  How this value is used depends on the
value of other customization variables or command line options, such
as whether the output is split and @code{NODE_FILENAMES}.  The default
is unset.

@item PROGRAM
Name of the program used.  By default, it is set to the name of the
program launched, with a trailing @samp{.pl} removed.

@item RENAMED_NODES_FILE
If set, use the value for the renamed nodes description file.  If not
set, the file is @file{@var{doc_basename}-noderename.cnf}.
@xref{HTML Xref Link Preservation}.

@item RENAMED_NODES_REDIRECTIONS
If set, create redirection files for renamed nodes.  Set by default
when generating HTML@.

@item SHOW_MENU
@vindex HEADERS
@opindex --no-headers
If set, Texinfo menus are output.  By default, it is set unless
generating Docbook or if @option{--no-headers} is specified.

@item SORT_ELEMENT_COUNT
@pindex texi-elements-by-size
@cindex Longest nodes, finding
@cindex Sorting nodes by size
If set, the name of a file to which a list of elements (nodes or
sections, depending on the output format) is dumped, sorted by the
number of lines they contain after removal of @@-commands; default
unset.  This is used by the program @code{texi-elements-by-size} in
the @file{util/} directory of the Texinfo source distribution
(@pxref{texi-elements-by-size}).

@item SORT_ELEMENT_COUNT_WORDS
When dumping the elements-by-size file (see preceding item), use word
counts instead of line counts; default false.

@c @item SPLIT_INDEX
@c For HTML@.  If set, the output is split, and the output from
@c @code{@@printindex} happens in a sectioning element at the level of
@c splitting, then split index pages at the next letter after they have
@c more than that many entries.  If set to 0, no index splitting.

@item TEST
If set to true, some variables which are normally dynamically
generated anew for each run (date, program name, version) are set to
fixed and given values.  This is useful to compare the output to a
reference file, as is done for the tests.  The default is false.

@item TEXI2DVI
Name of the command used to produce PostScript, PDF, and DVI; default
@samp{texi2dvi}.  @xref{@command{texi2any} Printed Output}.

@item TEXI2HTML
@cindex compatibility, with @command{texi2html}
Generate HTML and try to be as compatible as possible with
@command{texi2html}; default false.

@item TEXINFO_DTD_VERSION
For XML@.  Version of the DTD used in the XML output preamble.  The
default is set based on a variable in @file{configure.ac}.

@item TEXTCONTENT_COMMENT
For stripped text content output (i.e., when
@code{TEXINFO_OUTPUT_FORMAT} is set to @code{textcontent}).  If set,
also output comments.  Default false.

@item TOP_NODE_UP
Up node for the Top node; default @samp{(dir)}.  For overriding the
url in HTML output, see @code{TOP_NODE_UP_URL} in @ref{HTML
Customization Variables}.

@item TREE_TRANSFORMATIONS
The associated value is a comma separated list of transformations that
can be applied to the Texinfo tree prior to outputting the result.  If
more than one is specified, the ordering is irrelevant; each is always
applied at the necessary point during processing.

The only one executed by default is
@samp{move_index_entries_after_items} for HTML and Docbook output.
Here's an example of updating the master menu in a document:

@example
makeinfo \
  -c TREE_TRANSFORMATIONS=regenerate_master_menu \
  -c PLAINTEXINFO=1 \
  mydoc.texi \
  -o /tmp/out
@end example

@noindent (Caveat: Since @code{PLAINTEXINFO} output does expand
Texinfo macros and conditionals, it's necessary to remove any such
differences before installing the updates in the original document.
This will be remedied in a future release.)

The following transformations are currently supported (many are used
in the @code{pod2texi} utility distributed with Texinfo;
@pxref{Invoking @command{pod2texi}}):

@ftable @samp
@item complete_tree_nodes_menus
Add menu entries or whole menus for nodes associated with sections of
any level, based on the sectioning tree.

@item fill_gaps_in_sectioning
Adds empty @code{@@unnumbered...} sections in a tree to fill gaps in
sectioning.  For example, an @code{@@unnumberedsec} will be inserted
if a @code{@@chapter} is followed by a @code{@@subsection}.

@item insert_nodes_for_sectioning_commands
Insert nodes for sectioning commands lacking a corresponding node.

@item move_index_entries_after_items
In @code{@@enumerate} and @code{@@itemize}, move index entries
appearing just before an @code{@@item} to just after the
@code{@@item}.  Comment lines between index entries are moved too.  As
mentioned, this is always done for HTML and Docbook output.

@item regenerate_master_menu
Update the Top node master menu, either replacing the (first)
@code{@@detailmenu} in the Top node menu, or creating it at the end of
the Top node menu.

@item simple_menu
Mostly the same as @code{SIMPLE_MENU}: use a simple preformatted style
for the menu.  It differs from setting @code{SIMPLE_MENU} in that
@code{SIMPLE_MENU} only has an effect in HTML output.

@end ftable

@item USE_NODES
Preferentially use nodes to decide where elements are separated.  If
set to false, preferentially use sectioning to decide where elements
are separated.  The default is true.

@item USE_NODE_TARGET
If set, use the node associated with a section for the section target
in cross-references; default true.

@item USE_NUMERIC_ENTITY
For HTML and XML@.  If set, use numeric entities instead of ASCII
characters when there is no named entity.  By default, set to true for
HTML.

@item USE_UP_NODE_FOR_ELEMENT_UP
Fill in up sectioning direction with node direction when there is no
sectioning up direction.  In practice this can only happen when there
is no @@top section.  Not set by default.

@item USE_SETFILENAME_EXTENSION
Default is on for Info, off for other output.  If set, use exactly
what @code{@@setfilename} gives for the output file name, including
the extension.  You should not need to explicitly set this variable.

@item USE_TITLEPAGE_FOR_TITLE
Use the full @code{@@titlepage} as the title, not a simple title string;
default false.

@item USE_UNIDECODE
@pindex Text::Unidecode
If set to false, do not use the @code{Text::Unidecode} Perl module to
transliterate more characters; default true.

@end vtable

@node Internationalization of Document Strings
@section Internationalization of Document Strings

@cindex I18n, of document strings
@cindex Internationalization of document strings
@cindex Document strings, internationalization of
@cindex Output document strings, internationalization of
@cindex Translating strings in output documents

@vindex documentlanguage @r{customization variable}
@command{texi2any} writes fixed strings into the output document at
various places: cross-references, page footers, the help page,
alternate text for images, and so on.  The string chosen depends on
the value of the @code{documentlanguage} at the time of the string
being output (@pxref{@code{@@documentlanguage}}, for the Texinfo
command interface).

@pindex libintl-perl @r{Gettext implementation}
The Gettext framework is used for those strings (@pxref{Top,,,
gettext, Gettext}).  The @code{libintl-perl} package is used as the
@code{gettext} implementation; more specifically, the pure Perl
implementation is used, so Texinfo can support consistent behavior
across all platforms and installations, which would not otherwise be
possible.  @code{libintl-perl} is included in the Texinfo distribution
and always installed, to ensure that it is available if needed.  It is
also possible to use the system @code{gettext} (the choice can be made
at build-time).

@vindex texinfo_document @r{Gettext domain}
@cindex Perl format strings for translation
The Gettext domain @samp{texinfo_document} is used for the strings.
Translated strings are written as Texinfo, and may include
@@-commands.  In translated strings, the varying parts of the string
are not usually denoted by @code{%s} and the like, but by
@samp{@{arg_name@}}.  (This convention is common for @code{gettext} in
Perl and is fully supported in GNU Gettext; @pxref{perl-format,, Perl
Format Strings, gettext, GNU Gettext}.)  For example, in the
following, @samp{@{section@}} will be replaced by the section name:

@example
see @{section@}
@end example

These Perl-style brace format strings are used for two reasons: first,
changing the order of @code{printf} arguments is only available since
Perl@tie{}5.8.0; second, and more importantly, the order of arguments
is unpredictable, since @@-command expansion may lead to different
orders depending on the output format.

The expansion of a translation string is done like this:

@enumerate
@item First, the string is translated.  The locale
is @var{@@documentlanguage}@code{.}@var{@@documentencoding}.

@cindex @code{us-ascii} encoding, and translations
If the @var{@@documentlanguage} has the form @samp{ll_CC}, that is
tried first, and then just @samp{ll}.  If that does not exist, and the
encoding is not @code{us-ascii}, then @code{us-ascii} is tried.

The idea is that if there is a @code{us-ascii} encoding, it means that
all the characters in the charset may be expressed as @@-commands.
For example, there is a @code{fr.us-ascii} locale that can accommodate
any encoding, since all the Latin@tie{}1 characters have associated
@@-commands.  On the other hand, Japanese has only a translation
@code{ja.utf-8}, since there are no @@-commands for Japanese
characters.

@item Next, the string is expanded as Texinfo, and converted.
The arguments are substituted; for example, @samp{@{arg_name@}} is
replaced by the corresponding actual argument.

@end enumerate

In the following example, @samp{@{date@}}, @samp{@{program_homepage@}}
and @samp{@{program@}} are the arguments of the string.  Since they
are used in @code{@@uref}, their order is not predictable.
@samp{@{date@}}, @samp{@{program_homepage@}} and @samp{@{program@}} are
substituted after the expansion:

@example
Generated on @@emph@{@{date@}@} using
@@uref@{@{program_homepage@}, @@emph@{@{program@}@}@}.
@end example

This approach is admittedly a bit complicated.  Its usefulness is that
it supports having translations available in different encodings for
encodings which can be covered by @@-commands, and also specifying how
the formatting for some commands is done, independently of the output
format---yet still be language-dependent.  For example, the
@samp{@@pxref} translation string can be like this:

@example
see @{node_file_href@} section `@{section@}\' in @@cite@{@{book@}@}
@end example

@noindent
which allows for specifying a string independently of the output
format, while nevertheless with rich formatting it may be translated
appropriately in many languages.

@node Invoking @command{pod2texi}
@section Invoking @command{pod2texi}: Convert POD to Texinfo

@pindex pod2texi
@cindex Invoking @code{pod2texi}
@cindex POD, converting to Texinfo
@cindex Perl POD, converting to Texinfo

The @code{pod2texi} program translates Perl pod documentation file(s)
to Texinfo.  There are two basic modes of operation: generating a
standalone manual from each input pod, or (if @code{--base-level=1} or
higher is given) generating Texinfo subfiles suitable for use
with @code{@@include}.

Although ordinarily this documentation in the Texinfo manual would be
the best place to look, in this case we have documented all the
options and examples in the @code{pod2texi} program itself, since it
may be useful outside of the rest of Texinfo.  Thus, please see the
output of @code{pod2texi --help}, the version on the web at
@url{http://www.gnu.org/software/texinfo/manual/pod2texi.html}, etc.

For an example of using @code{pod2texi} to make Texinfo out of the
Perl documentation itself, see
@url{http://svn.savannah.gnu.org/viewvc/trunk/contrib/perldoc-all/?root=texinfo,
@file{contrib/perldoc-all}} in the Texinfo source distribution (the
output is available at @url{http://www.gnu.org/software/perl/manual}).

@node @command{texi2html}
@section @command{texi2html}: Ancestor of @command{texi2any}

@pindex texi2html

@cindex Cons, Lionel
Conceptually, the @command{texi2html} program is the parent of today's
@command{texi2any} program.  @command{texi2html} was developed
independently, originally by Lionel Cons in 1998; at the time,
@command{makeinfo} could not generate HTML@.  Many other people
contributed to @command{texi2html} over the years.

The present @command{texi2any} uses little of the actual code of
@command{texi2html}, and has quite a different basic approach to the
implementation (namely, parsing the Texinfo document into a tree), but
still, there is a family resemblance.

By design, @command{texi2any} supports nearly all the features of
@command{texi2html} in some way.  However, we did not attempt to
maintain strict compatibility, so no @command{texi2html} executable is
installed by the Texinfo package.  An approximation can be run with an
invocation like this (available as @file{util/texi2html} in the
Texinfo source):

@example
texi2any --set-customization-variable TEXI2HTML=1 ...
@end example

@noindent but, to emphasize, this is @emph{not} a drop-in replacement
for the previous @command{texi2html}.  Here are the biggest differences:

@itemize @bullet
@item Most blatantly, the command line options of @command{texi2html}
are now customization variables, for the most part.  A table of
approximate equivalents is given below.

@item The program-level customization API is very different in
@command{texi2any}.

@item Indices cannot be split.

@item Translated strings cannot be customized; we hope to introduce
this feature in @command{texi2any} in the future.

@end itemize

Aside from the last, we do not intend to reimplement these
differences.  Therefore, the route forward for authors is alter
manuals and build processes as necessary to use the new features and
methods of @command{texi2any}.  The @command{texi2html} maintainers
(one of whom is the principal author of @command{texi2any}) do not
intend to make further releases.

@cindex Options of @command{texi2html}
@cindex Command-line options of @command{texi2html}
Here is the table showing @command{texi2html} options and
corresponding @command{texi2any} customization variables.
@c (@pxref{texi2any Output Customization,, @command{texi2any} Output
@c Customization}).

@multitable {@option{--ignore-preamble-text}} {@code{IGNORE_PREAMBLE_TEXT}}
@item @option{--toc-links}            @tab @code{TOC_LINKS}
@item @option{--short-ext}            @tab @code{SHORTEXTN}
@item @option{--prefix}               @tab @code{PREFIX}
@item @option{--short-ref}            @tab @code{SHORT_REF}
@item @option{--idx-sum}              @tab @code{IDX_SUMMARY}
@item @option{--def-table}            @tab @code{DEF_TABLE}
@item @option{--ignore-preamble-text} @tab @code{IGNORE_PREAMBLE_TEXT}
@item @option{--html-xref-prefix}     @tab @code{EXTERNAL_DIR}
@item @option{--l2h}                  @tab @code{L2H}
@item @option{--l2h-l2h}              @tab @code{L2H_L2H}
@item @option{--l2h-skip}             @tab @code{L2H_SKIP}
@item @option{--l2h-tmp}              @tab @code{L2H_TMP}
@item @option{--l2h-file}             @tab @code{L2H_FILE}
@item @option{--l2h-clean}            @tab @code{L2H_CLEAN}
@item @option{--use-nodes}            @tab @code{USE_NODES}
@item @option{--monolithic}           @tab @code{MONOLITHIC}
@item @option{--top-file}             @tab @code{TOP_FILE}
@item @option{--toc-file}             @tab @code{TOC_FILE}
@item @option{--frames}               @tab @code{FRAMES}
@item @option{--menu}                 @tab @code{SHOW_MENU}
@item @option{--debug}                @tab @code{DEBUG}
@item @option{--doctype}              @tab @code{DOCTYPE}
@item @option{--frameset-doctype}     @tab @code{FRAMESET_DOCTYPE}
@item @option{--test}                 @tab @code{TEST}
@end multitable

@cindex @file{texi2oldapi.texi}, for @command{texi2any}
Finally, any @command{texi2html} users seeking more detailed
information can check the draft file @file{doc/texi2oldapi.texi} in
the Texinfo source repository.  It consists mainly of very rough
notes, but may still be useful to some.

@node Creating and Installing Info Files
@chapter Creating and Installing Info Files

This chapter describes how to create and install Info files.
@xref{Info Files}, for general information about the file format
itself.

@menu
* Creating an Info File::
* Installing an Info File::
@end menu

@node Creating an Info File
@section Creating an Info File
@cindex Creating an Info file
@cindex Info, creating an online file
@cindex Formatting a file for Info

@code{makeinfo} is a program that converts a Texinfo file into an Info
file, HTML file, or plain text.  @code{texinfo-format-region} and
@code{texinfo-format-buffer} are GNU Emacs functions that convert
Texinfo to Info.

For information on installing the Info file in the Info system,
@pxref{Installing an Info File}.

@menu
* @command{makeinfo} Advantages::         @command{makeinfo} provides better error checking.
* @code{makeinfo} in Emacs::           How to run @code{makeinfo} from Emacs.
* @code{texinfo-format} commands::     Two Info formatting commands written
                                 in Emacs Lisp are an alternative
                                 to @code{makeinfo}.
* Batch Formatting::            How to format for Info in Emacs batch mode.
* Tag and Split Files::         How tagged and split files help Info
                                 to run better.
@end menu

@node @command{makeinfo} Advantages
@subsection @code{makeinfo} Advantages

@anchor{makeinfo advantages}@c old name

The @code{makeinfo} utility creates an Info file from a Texinfo source
providing better error messages than either of the Emacs formatting
commands.  We recommend it.  The @code{makeinfo} program is
independent of Emacs.  You can run @code{makeinfo} in any of three
ways: from an operating system shell, from a shell inside Emacs, or by
typing the @kbd{C-c C-m C-r} or the @kbd{C-c C-m C-b} command in
Texinfo mode in Emacs.

The @code{texinfo-format-region} and the @code{texinfo-format-buffer}
commands may be useful if you cannot run @code{makeinfo}.

@node @code{makeinfo} in Emacs
@subsection Running @code{makeinfo} Within Emacs

@c anchor{makeinfo in Emacs}@c prev name
@cindex Running @code{makeinfo} in Emacs
@cindex @code{makeinfo} inside Emacs
@cindex Shell, running @code{makeinfo} in

You can run @code{makeinfo} in GNU Emacs Texinfo mode by using either the
@code{makeinfo-region} or the @code{makeinfo-buffer} commands.  In
Texinfo mode, the commands are bound to @kbd{C-c C-m C-r} and @kbd{C-c
C-m C-b} by default.

@table @kbd
@item C-c C-m C-r
@itemx M-x makeinfo-region
Format the current region for Info.
@findex makeinfo-region

@item C-c C-m C-b
@itemx M-x makeinfo-buffer
Format the current buffer for Info.
@findex makeinfo-buffer
@end table

When you invoke @code{makeinfo-region} the output goes to a temporary
buffer.  When you invoke @code{makeinfo-buffer} output goes to the
file set with @code{@@setfilename} (@pxref{@code{@@setfilename}}).

The Emacs @code{makeinfo-region} and @code{makeinfo-buffer} commands
run the @code{makeinfo} program in a temporary shell buffer.  If
@code{makeinfo} finds any errors, Emacs displays the error messages in
the temporary buffer.

@cindex Errors, parsing
@cindex Parsing errors
@findex next-error
You can parse the error messages by typing @kbd{C-x `}
(@code{next-error}).  This causes Emacs to go to and position the
cursor on the line in the Texinfo source that @code{makeinfo} thinks
caused the error.  @xref{Compilation, , Running @code{make} or
Compilers Generally, emacs, The GNU Emacs Manual}, for more
information about using the @code{next-error} command.

In addition, you can kill the shell in which the @code{makeinfo}
command is running or make the shell buffer display its most recent
output.

@table @kbd
@item C-c C-m C-k
@itemx M-x makeinfo-kill-job
@findex makeinfo-kill-job
Kill the current running @code{makeinfo} job
(from @code{makeinfo-region} or @code{makeinfo-buffer}).

@item C-c C-m C-l
@itemx M-x makeinfo-recenter-output-buffer
@findex makeinfo-recenter-output-buffer
Redisplay the @code{makeinfo} shell buffer to display its most recent
output.
@end table

@noindent
(Note that the parallel commands for killing and recentering a @TeX{}
job are @kbd{C-c C-t C-k} and @kbd{C-c C-t C-l}.  @xref{Texinfo Mode
Printing}.)

You can specify options for @code{makeinfo} by setting the
@code{makeinfo-options} variable with either the @kbd{M-x
customize} or the @kbd{M-x set-variable} command, or by setting the
variable in your @file{.emacs} initialization file.

For example, you could write the following in your @file{.emacs} file:

@example
@group
(setq makeinfo-options
     "--paragraph-indent=0 --no-split
      --fill-column=70 --verbose")
@end group
@end example

@noindent
@c Writing these three cross-references using xref results in
@c three references to the same named manual, which looks strange.
@iftex
For more information, see @ref{@command{makeinfo} Options}, as well as
``Easy Customization Interface,'' ``Examining and Setting Variables,''
and ``Init File'' in @cite{The GNU Emacs Manual}.
@end iftex
@ifnottex
For more information, see@*
@ref{Easy Customization, , Easy Customization Interface, emacs, The GNU Emacs Manual},@*
@ref{Examining, , Examining and Setting Variables, emacs, The GNU Emacs Manual},@*
@ref{Init File, , , emacs, The GNU Emacs Manual}, and@*
@ref{@command{makeinfo} Options}.
@end ifnottex

@node @code{texinfo-format} commands
@subsection The @code{texinfo-format@dots{}} Commands

@c anchor{texinfo-format commands}@c prev name

In GNU Emacs in Texinfo mode, you can format part or all of a Texinfo
file with the @code{texinfo-format-region} command.  This formats the
current region and displays the formatted text in a temporary buffer
called @samp{*Info Region*}.

Similarly, you can format a buffer with the
@code{texinfo-format-buffer} command.  This command creates a new
buffer and generates the Info file in it.  Typing @kbd{C-x C-s} will
save the Info file under the name specified by the
@code{@@setfilename} line which must be near the beginning of the
Texinfo file.

@table @kbd
@item C-c C-e C-r
@itemx @code{texinfo-format-region}
@findex texinfo-format-region
Format the current region for Info.

@item C-c C-e C-b
@itemx @code{texinfo-format-buffer}
@findex texinfo-format-buffer
Format the current buffer for Info.
@end table

The @code{texinfo-format-region} and @code{texinfo-format-buffer}
commands provide you with some error checking, and other functions can
provide you with further help in finding formatting errors.  These
procedures are described in an appendix; see @ref{Catching Mistakes}.
However, the @code{makeinfo} program provides better error checking
(@pxref{@code{makeinfo} in Emacs}).

A peculiarity of the @code{texinfo-format-buffer} and
@code{texinfo-format-region} commands is that they do not indent (nor
fill) paragraphs that contain @code{@@w} or @code{@@*} commands.

@node Batch Formatting
@subsection Batch Formatting
@cindex Batch formatting for Info
@cindex Info batch formatting

You can format Texinfo files for Info using @code{batch-texinfo-format}
and Emacs batch mode.  You can run Emacs in batch mode from any shell,
including a shell inside of Emacs.  (@xref{Initial Options,,,
emacs, The GNU Emacs Manual}.)

Here is a shell command to format all the files that end in
@file{.texinfo} in the current directory:

@example
emacs -batch -funcall batch-texinfo-format *.texinfo
@end example

@noindent
Emacs processes all the files listed on the command line, even if an
error occurs while attempting to format some of them.

Run @code{batch-texinfo-format} only with Emacs in batch mode as shown;
it is not interactive.  It kills the batch mode Emacs on completion.

@code{batch-texinfo-format} is convenient if you lack @code{makeinfo}
and want to format several Texinfo files at once.  When you use Batch
mode, you create a new Emacs process.  This frees your current Emacs, so
you can continue working in it.  (When you run
@code{texinfo-format-region} or @code{texinfo-format-buffer}, you cannot
use that Emacs for anything else until the command finishes.)

@node Tag and Split Files
@subsection Tag Files and Split Files
@cindex Making a tag table automatically
@cindex Tag table, making automatically

If a Texinfo file has more than 30,000 bytes,
@code{texinfo-format-buffer} automatically creates a tag table
for its Info file; @code{makeinfo} always creates a tag table.  With
a @dfn{tag table}, Info can jump to new nodes more quickly than it can
otherwise.

@cindex Indirect subfiles
In addition, if the Texinfo file contains more than about 300,000
bytes, @code{texinfo-format-buffer} and @code{makeinfo} split the
large Info file into shorter @dfn{indirect} subfiles of about 300,000
bytes each.  Big files are split into smaller files so that Emacs does
not need to make a large buffer to hold the whole of a large Info
file; instead, Emacs allocates just enough memory for the small, split-off
file that is needed at the time.  This way, Emacs avoids wasting
memory when you run Info.  (Before splitting was implemented, Info
files were always kept short and @dfn{include files} were designed as
a way to create a single, large printed manual out of the smaller Info
files.  @xref{Include Files}, for more information.  Include files are
still used for very large documents, such as @cite{The Emacs Lisp
Reference Manual}, in which each chapter is a separate file.)

When a file is split, Info itself makes use of a shortened version of
the original file that contains just the tag table and references to
the files that were split off.  The split-off files are called
@dfn{indirect} files.

The split-off files have names that are created by appending @w{@samp{-1}},
@w{@samp{-2}}, @w{@samp{-3}} and so on to the file name specified by the
@code{@@setfilename} command.  The shortened version of the original file
continues to have the name specified by @code{@@setfilename}.

At one stage in writing this document, for example, the Info file was saved
as the file @file{test-texinfo} and that file looked like this:

@example
@group
Info file: test-texinfo,    -*-Text-*-
produced by texinfo-format-buffer
from file: new-texinfo-manual.texinfo

^_
Indirect:
test-texinfo-1: 102
test-texinfo-2: 50422
@end group
@group
test-texinfo-3: 101300
^_^L
Tag table:
(Indirect)
Node: overview^?104
Node: info file^?1271
@end group
@group
Node: printed manual^?4853
Node: conventions^?6855
@dots{}
@end group
@end example

@noindent
(But @file{test-texinfo} had far more nodes than are shown here.)  Each of
the split-off, indirect files, @file{test-texinfo-1},
@file{test-texinfo-2}, and @file{test-texinfo-3}, is listed in this file
after the line that says @samp{Indirect:}.  The tag table is listed after
the line that says @samp{Tag table:}.

In the list of indirect files, the number following the file name
records the cumulative number of bytes in the preceding indirect
files, not counting the file list itself, the tag table, or any
permissions text in the first file.  In the tag table, the number
following the node name records the location of the beginning of the
node, in bytes from the beginning of the (unsplit) output.

If you are using @code{texinfo-format-buffer} to create Info files,
you may want to run the @code{Info-validate} command.  (The
@code{makeinfo} command does such a good job on its own, you do not
need @code{Info-validate}.)  However, you cannot run the @kbd{M-x
Info-validate} node-checking command on indirect files.  For
information on how to prevent files from being split and how to
validate the structure of the nodes, see @ref{Using
@code{Info-validate}}.

@node Installing an Info File
@section Installing an Info File
@cindex Installing an Info file
@cindex Info file installation
@cindex @file{dir} directory for Info installation

Info files are usually kept in the @file{info} directory.  You can
read Info files using the standalone Info program or the Info reader
built into Emacs.  (@xref{Top,,, info, Info}, for an introduction to
Info.)

@menu
* Directory File::              The top level menu for all Info files.
* New Info File::               Listing a new Info file.
* Other Info Directories::      How to specify Info files that are
                                 located in other directories.
* Installing Dir Entries::      How to specify what menu entry to add
                                 to the Info directory.
* Invoking @command{install-info}::       @code{install-info} options.
@end menu

@node Directory File
@subsection The Directory File @file{dir}

For Info to work, the @file{info} directory must contain a file that
serves as a top level directory for the Info system.  By convention,
this file is called @file{dir}.  (You can find the location of this file
within Emacs by typing @kbd{C-h i} to enter Info and then typing
@kbd{C-x C-f} to see the pathname to the @file{info} directory.)

The @file{dir} file is itself an Info file.  It contains the top level
menu for all the Info files in the system.  The menu looks like
this:

@example
@group
* Menu:
* Info:    (info).     Documentation browsing system.
* Emacs:   (emacs).    The extensible, self-documenting
                      text editor.
* Texinfo: (texinfo).  With one source file, make
                      either a printed manual using
                      @@TeX@{@} or an Info file.
@dots{}
@end group
@end example

Each of these menu entries points to the `Top' node of the Info file
that is named in parentheses.  (The menu entry does not need to
specify the `Top' node, since Info goes to the `Top' node if no node
name is mentioned.  @xref{Other Info Files, , Nodes in Other Info
Files}.)

Thus, the @samp{Info} entry points to the `Top' node of the
@file{info} file and the @samp{Emacs} entry points to the `Top' node
of the @file{emacs} file.

In each of the Info files, the `Up' pointer of the `Top' node refers
back to the @code{dir} file.  For example, the line for the `Top'
node of the Emacs manual looks like this in Info:

@example
File: emacs  Node: Top, Up: (DIR), Next: Distrib
@end example

@noindent
In this case, the @file{dir} file name is written in uppercase
letters---it can be written in either upper- or lowercase.  This is not
true in general, it is a special case for @file{dir}.

@node New Info File
@subsection Listing a New Info File
@cindex Adding a new Info file
@cindex Listing a new Info file
@cindex New Info file, listing it in @file{dir} file
@cindex Info file, listing a new
@cindex @file{dir} file listing

To add a new Info file to your system, you must write a menu entry to
add to the menu in the @file{dir} file in the @file{info} directory.
For example, if you were adding documentation for GDB, you would write
the following new entry:

@example
* GDB: (gdb).           The source-level C debugger.
@end example

@noindent
The first part of the menu entry is the menu entry name, followed by a
colon.  The second part is the name of the Info file, in parentheses,
followed by a period.  The third part is the description.

The name of an Info file often has a @file{.info} extension.  Thus, the
Info file for GDB might be called either @file{gdb} or @file{gdb.info}.
The Info reader programs automatically try the file name both with and
without @file{.info}@footnote{On MS-DOS/MS-Windows systems, Info will
try the @file{.inf} extension as well.}; so it is better to avoid
clutter and not to write @samp{.info} explicitly in the menu entry.  For
example, the GDB menu entry should use just @samp{gdb} for the file
name, not @samp{gdb.info}.

@node Other Info Directories
@subsection Info Files in Other Directories
@cindex Installing Info in another directory
@cindex Info installed in another directory
@cindex Another Info directory
@cindex @file{dir} files and Info directories

If an Info file is not in the @file{info} directory, there are three
ways to specify its location:

@enumerate
@item
Write the pathname in the @file{dir} file as the second part of the menu.

@item
Specify the Info directory name in the @code{INFOPATH} environment
variable in your @file{.profile} or @file{.cshrc} initialization file.
(Only you and others who set this environment variable will be able to
find Info files whose location is specified this way.)

@item
If you are using Emacs, list the name of the file in a second @file{dir}
file, in its directory; and then add the name of that directory to the
@code{Info-directory-list} variable in your personal or site
initialization file.

This variable tells Emacs where to look for @file{dir} files (the files
must be named @file{dir}).  Emacs merges the files named @file{dir} from
each of the listed directories.  (In Emacs version 18, you can set the
@code{Info-directory} variable to the name of only one
directory.)
@end enumerate

For example, to reach a test file in the @file{/home/bob/info}
directory, you could add an entry like this to the menu in the
standard @file{dir} file:

@example
* Test: (/home/bob/info/info-test).  Bob's own test file.
@end example

@noindent
In this case, the absolute file name of the @file{info-test} file is
written as the second part of the menu entry.

@vindex INFOPATH
@cindex Environment variable @code{INFOPATH}
If you don't want to edit the system @file{dir} file, you can tell
Info where to look by setting the @code{INFOPATH} environment variable
in your shell startup file.  This works with both the Emacs and
standalone Info readers.

Specifically, if you use a Bourne-compatible shell such as @code{sh}
or @code{bash} for your shell command interpreter, you set the
@code{INFOPATH} environment variable in the @file{.profile}
initialization file; but if you use @code{csh} or @code{tcsh}, you set
the variable in the @file{.cshrc} initialization file.  On
MS-DOS/MS-Windows systems, you must set @code{INFOPATH} in your
@file{autoexec.bat} file or in the registry.  Each type of shell uses
a different syntax.

@itemize @bullet
@item
In a @file{.cshrc} file, you could set the @code{INFOPATH}
variable as follows:

@smallexample
setenv INFOPATH .:~/info:/usr/local/emacs/info
@end smallexample

@item
In a @file{.profile} file, you would achieve the same effect by writing:

@smallexample
INFOPATH=.:$HOME/info:/usr/local/emacs/info
export INFOPATH
@end smallexample

@item
@pindex autoexec.bat
In a @file{autoexec.bat} file, you write this command (note the
use of @samp{;} as the directory separator, and a different syntax for
using values of other environment variables):

@smallexample
set INFOPATH=.;%HOME%/info;c:/usr/local/emacs/info
@end smallexample
@end itemize

@noindent
The @samp{.} indicates the current directory as usual.  Emacs uses the
@code{INFOPATH} environment variable to initialize the value of Emacs's
own @code{Info-directory-list} variable.  The standalone Info reader
merges any files named @file{dir} in any directory listed in the
@env{INFOPATH} variable into a single menu presented to you in the node
called @samp{(dir)Top}.

@cindex Colon, last in @env{INFOPATH}
However you set @env{INFOPATH}, if its last character is a colon (on
MS-DOS/MS-Windows systems, use a semicolon instead), this is replaced
by the default (compiled-in) path.  This gives you a way to augment
the default path with new directories without having to list all the
standard places.  For example (using @code{sh} syntax):

@example
INFOPATH=/home/bob/info:
export INFOPATH
@end example

@noindent
will search @file{/home/bob/info} first, then the standard directories.
Leading or doubled colons are not treated specially.

@cindex @file{dir} file, creating your own
When you create your own @file{dir} file for use with
@code{Info-directory-list} or @env{INFOPATH}, it's easiest to start by
copying an existing @file{dir} file and replace all the text after the
@samp{* Menu:} with your desired entries.  That way, the punctuation
and special @kbd{CTRL-_} characters that Info needs will be present.

As one final alternative, which works only with Emacs Info, you can
change the @code{Info-directory-list} variable.  For example:

@example
(add-hook 'Info-mode-hook '(lambda ()
	     (add-to-list 'Info-directory-list
			  (expand-file-name "~/info"))))
@end example

@node Installing Dir Entries
@subsection Installing Info Directory Files

When you install an Info file onto your system, you can use the program
@code{install-info} to update the Info directory file @file{dir}.
Normally the makefile for the package runs @code{install-info}, just
after copying the Info file into its proper installed location.

@findex dircategory
@findex direntry
In order for the Info file to work with @code{install-info}, you include
the commands @code{@@dircategory} and
@code{@@direntry}@dots{}@code{@@end direntry} in the Texinfo source
file.  Use @code{@@direntry} to specify the menu entries to add to the
Info directory file, and use @code{@@dircategory} to specify which part
of the Info directory to put it in.  Here is how these commands are used
in this manual:

@smallexample
@@dircategory Texinfo documentation system
@@direntry
* Texinfo: (texinfo).           The GNU documentation format.
* install-info: (texinfo)Invoking install-info. @dots{}
@dots{}
@@end direntry
@end smallexample

Here's what this produces in the Info file:

@smallexample
INFO-DIR-SECTION Texinfo documentation system
START-INFO-DIR-ENTRY
* Texinfo: (texinfo).           The GNU documentation format.
* install-info: (texinfo)Invoking install-info. @dots{}
@dots{}
END-INFO-DIR-ENTRY
@end smallexample

@noindent
The @code{install-info} program sees these lines in the Info file, and
that is how it knows what to do.

Always use the @code{@@direntry} and @code{@@dircategory} commands near
the beginning of the Texinfo input, before the first @code{@@node}
command.  If you use them later on in the input, @code{install-info}
will not notice them.

@code{install-info} will automatically reformat the description of the
menu entries it is adding.  As a matter of convention, the description
of the main entry (above, @samp{The GNU documentation format}) should
start at column 32, starting at zero (as in
@code{what-cursor-position} in Emacs).  This will make it align with
most others.  Description for individual utilities best start in
column 48, where possible.  For more information about formatting see
the @samp{--calign}, @samp{--align}, and @samp{--max-width} options in
@ref{Invoking @command{install-info}}.

If you use @code{@@dircategory} more than once in the Texinfo source,
each usage specifies the `current' category; any subsequent
@code{@@direntry} commands will add to that category.

@cindex Free Software Directory
@cindex Dir categories, choosing
@cindex Categories, choosing
When choosing a category name for the @code{@@dircategory} command, we
recommend consulting the @uref{http://www.gnu.org/directory,
Free Software Directory}.  If your program is not listed there,
or listed incorrectly or incompletely, please report the situation to
the directory maintainers (@url{http://directory.fsf.org}) so that the
category names can be kept in sync.

Here are a few examples (see the @file{util/dir-example} file in the
Texinfo distribution for large sample @code{dir} file):

@display
Emacs
Localization
Printing
Software development
Software libraries
Text creation and manipulation
@end display

@cindex Invoking nodes, including in dir file
Each `Invoking' node for every program installed should have a
corresponding @code{@@direntry}.  This lets users easily find the
documentation for the different programs they can run, as with the
traditional @command{man} system.

@node Invoking @command{install-info}
@subsection Invoking @command{install-info}

@pindex install-info

@code{install-info} inserts menu entries from an Info file into the
top-level @file{dir} file in the Info system (see the previous sections
for an explanation of how the @file{dir} file works).  @code{install-info}
also removes menu entries from the @file{dir} file.  It's most often
run as part of software installation, or when constructing a @file{dir} file
for all manuals on a system.  Synopsis:

@example
install-info [@var{option}@dots{}] [@var{info-file} [@var{dir-file}]]
@end example

If @var{info-file} or @var{dir-file} are not specified, the options
(described below) that define them must be.  There are no compile-time
defaults, and standard input is never used.  @code{install-info} can
read only one Info file and write only one @file{dir} file per invocation.

@cindex @file{dir}, created by @code{install-info}
If @var{dir-file} (however specified) does not exist,
@code{install-info} creates it if possible (with no entries).

@cindex Compressed dir files, reading
@cindex XZ-compressed dir files, reading
@cindex Bzipped dir files, reading
@cindex Lzip-compressed dir files, reading
@cindex LZMA-compressed dir files, reading
@cindex Dir files, compressed
If any input file is compressed with @code{gzip} (@pxref{Top,,, gzip,
Gzip}), @code{install-info} automatically uncompresses it for reading.
And if @var{dir-file} is compressed, @code{install-info} also
automatically leaves it compressed after writing any changes.  If
@var{dir-file} itself does not exist, @code{install-info} tries to
open @file{@var{dir-file}.gz}, @file{@var{dir-file}.xz},
@file{@var{dir-file}.bz2}, @file{@var{dir-file}.lz}, and
@file{@var{dir-file}.lzma}, in that order.

Options:

@table @code
@item --add-once
@opindex --add-once@r{, for @command{install-info}}
Specifies that the entry or entries will only be put into a single section.

@item --align=@var{column}
@opindex --align=@var{column}@r{, for @command{install-info}}
Specifies the column that the second and subsequent lines of menu entry's
description will be formatted to begin at.  The default for this option is
@samp{35}.  It is used in conjunction with the @samp{--max-width} option.
@var{column} starts counting at 1.

@item --append-new-sections
@opindex --append-new-sections@r{, for @command{install-info}}
Instead of alphabetizing new sections, place them at the end of the DIR file.

@item --calign=@var{column}
@opindex --calign=@var{column}@r{, for @command{install-info}}
Specifies the column that the first line of menu entry's description will
be formatted to begin at.  The default for this option is @samp{33}.  It is
used in conjunction with the @samp{--max-width} option.
When the name of the menu entry exceeds this column, entry's description
will start on the following line.
@var{column} starts counting at 1.

@item --debug
@opindex --debug@r{, for @command{install-info}}
Report what is being done.

@item --delete
@opindex --delete@r{, for @command{install-info}}
Delete the entries in @var{info-file} from @var{dir-file}.  The file
name in the entry in @var{dir-file} must be @var{info-file} (except for
an optional @samp{.info} in either one).  Don't insert any new entries.
Any empty sections that result from the removal are also removed.

@item --description=@var{text}
@opindex --description=@var{text}@r{, for @command{install-info}}
Specify the explanatory portion of the menu entry.  If you don't specify
a description (either via @samp{--entry}, @samp{--item} or this option),
the description is taken from the Info file itself.

@item --dir-file=@var{name}
@opindex --dir-file=@var{name}@r{, for @command{install-info}}
Specify file name of the Info directory file.  This is equivalent to
using the @var{dir-file} argument.

@item --dry-run
@opindex --dry-run@r{, for @command{install-info}}
Same as @samp{--test}.

@item --entry=@var{text}
@opindex --entry=@var{text}@r{, for @command{install-info}}
Insert @var{text} as an Info directory entry; @var{text} should have the
form of an Info menu item line plus zero or more extra lines starting
with whitespace.  If you specify more than one entry, they are all
added.  If you don't specify any entries, they are determined from
information in the Info file itself.

@item --help
@opindex --help@r{, for @command{texindex}}
Display a usage message with basic usage and all available options,
then exit successfully.

@item --info-file=@var{file}
@opindex --info-file=@var{file}@r{, for @command{install-info}}
Specify Info file to install in the directory.  This is
equivalent to using the @var{info-file} argument.

@item --info-dir=@var{dir}
@opindex --info-dir=@var{dir}@r{, for @command{install-info}}
Specify the directory where the directory file @file{dir} resides.
Equivalent to @samp{--dir-file=@var{dir}/dir}.

@item --infodir=@var{dir}
@opindex --infodir=@var{dir}@r{, for @command{install-info}}
Same as @samp{--info-dir}.

@item --item=@var{text}
@opindex --item=@var{text}@r{, for @command{install-info}}
Same as @samp{--entry=@var{text}}.  An Info directory entry is actually
a menu item.

@item --keep-old
@opindex --keep-old@r{, for @command{install-info}}
Do not replace pre-existing menu entries.  When @samp{--remove} is specified,
this option means that empty sections are not removed.

@item --max-width=@var{column}
@opindex --max-width=@var{column}@r{, for @command{install-info}}
Specifies the column that the menu entry's description will be word-wrapped
at.  @var{column} starts counting at 1.

@item --maxwidth=@var{column}
@opindex --maxwidth=@var{column}@r{, for @command{install-info}}
Same as @samp{--max-width}.

@item --menuentry=@var{text}
@opindex --menuentry=@var{text}@r{, for @command{install-info}}
Same as @samp{--name}.

@item --name=@var{text}
@opindex --name=@var{text}@r{, for @command{install-info}}
Specify the name portion of the menu entry.  If the @var{text} does
not start with an asterisk @samp{*}, it is presumed to be the text
after the @samp{*} and before the parentheses that specify the Info
file.  Otherwise @var{text} is taken verbatim, and is taken as
defining the text up to and including the first period (a space is
appended if necessary).  If you don't specify the name (either via
@samp{--entry}, @samp{--item} or this option), it is taken from the
Info file itself.  If the Info does not contain the name, the basename
of the Info file is used.

@item --no-indent
@opindex --no-indent@r{, for @command{install-info}}
Suppress formatting of new entries into the @file{dir} file.

@item --quiet
@itemx --silent
@opindex --quiet@r{, for @command{install-info}}
@opindex --silent@r{, for @command{install-info}}
Suppress warnings, etc., for silent operation.

@item --remove
@opindex --remove@r{, for @command{install-info}}
Same as @samp{--delete}.

@item --remove-exactly
@opindex --remove-exactly@r{, for @command{install-info}}
Also like @samp{--delete}, but only entries if the Info file name
matches exactly; @code{.info} and/or @code{.gz} suffixes are
@emph{not} ignored.

@item --section=@var{sec}
@opindex --section=@var{sec}@r{, for @command{install-info}}
Put this file's entries in section @var{sec} of the directory.  If you
specify more than one section, all the entries are added in each of the
sections.  If you don't specify any sections, they are determined from
information in the Info file itself.  If the Info file doesn't specify
a section, the menu entries are put into the Miscellaneous section.

@item --section @var{regex} @var{sec}
@opindex --section @var{regex} @var{sec}@r{, for @command{install-info}}
Same as @samp{--regex=@var{regex} --section=@var{sec} --add-once}.

@code{install-info} tries to detect when this alternate syntax is used,
but does not always guess correctly.  Here is the heuristic that
@code{install-info} uses:
@enumerate
@item
If the second argument to @code{--section} starts with a hyphen, the
original syntax is presumed.

@item
If the second argument to @code{--section} is a file that can be
opened, the original syntax is presumed.

@item
Otherwise the alternate syntax is used.
@end enumerate

When the heuristic fails because your section title starts with a
hyphen, or it happens to be a filename that can be opened, the syntax
should be changed to @samp{--regex=@var{regex} --section=@var{sec}
--add-once}.

@item --regex=@var{regex}
@opindex  --regex=@var{regex}@r{, for @command{install-info}}
Put this file's entries into any section that matches @var{regex}.  If
more than one section matches, all of the entries are added in each of the
sections.  Specify @var{regex} using basic regular expression syntax, more
or less as used with @command{grep}, for example.

@item --test
@opindex --test@r{, for @command{install-info}}
Suppress updating of the directory file.

@item --version
@opindex --version@r{, for @command{install-info}}
@cindex Version number, for install-info
Display version information and exit successfully.

@end table

@node Generating HTML
@chapter Generating HTML

@cindex Generating HTML
@cindex Outputting HTML

@command{makeinfo} generates Info output by default, but given the
@option{--html} option, it will generate HTML, for web browsers and
other programs.  This chapter gives some details on such HTML output.

@command{makeinfo} has many user-definable customization variables
with which you can influence the HTML output.  @xref{Customization
Variables}.

@command{makeinfo} can also produce output in XML and Docbook formats,
but we do not as yet describe these in detail.  @xref{Output Formats},
for a brief overview of all the output formats.

@menu
* HTML Translation::       Details of the HTML output.
* HTML Splitting::         How HTML output is split.
* HTML CSS::               Influencing HTML output with Cascading Style Sheets.
* HTML Xref::              Cross-references in HTML output.
@end menu

@node HTML Translation
@section HTML Translation

@cindex HTML translation

@cindex HTML output, browser compatibility of
First, the HTML generated by @command{makeinfo} is standard
HTML@tie{}4.  It also tries to be compatible with earlier standards
(e.g., HTML@tie{}2.0, RFC-1866).  Thus, please report output from an
error-free run of @code{makeinfo} which has practical browser
portability problems as a bug (@pxref{Reporting Bugs}).

@pindex html32.pm
Some known exceptions to HTML@tie{}3.2 (using
@samp{--init-file=html32.pm} produces strict HTML@tie{}3.2 output;
@pxref{Invoking @command{texi2any}}):

@enumerate
@item
HTML@tie{}3.2 tables are generated for the @code{@@multitable} command
(@pxref{Multi-column Tables}), but they should degrade reasonably in
browsers without table support.

@item
The HTML@tie{}4 @samp{lang} attribute on the @samp{<html>} attribute
is used.

@item
Entities that are not in the HTML@tie{}3.2 standard are also used.

@item
CSS is used (@pxref{HTML CSS}).

@item
A few HTML@tie{}4 elements are used: @code{thead}, @code{abbr},
@code{acronym}.

@end enumerate

To achieve maximum portability and accessibility among browsers (both
graphical and text-based), systems, and users, the HTML output is
intentionally quite plain and generic.  It has always been our goal
for users to be able to customize the output to their wishes via CSS
(@pxref{HTML CSS}) or other means (@pxref{Customization Variables}).
If you cannot accomplish a reasonable customization, feel free to
report that.

However, we do not wish to depart from our basic goal of widest
readability for the core output.  For example, using fancy CSS may
make it possible for the HTML output to more closely resemble the
@TeX{} output in some details, but this result is not even close to
being worth the ensuing difficulties.

It is also intentionally not our goal, and not even possible, to pass
through every conceivable validation test without any diagnostics.
Different validation tests have different goals, often about pedantic
enforcement of some standard or another.  Our overriding goal is to
help users, not blindly comply with standards.

To repeat what was said at the top: please report output from an
error-free run of @code{makeinfo} which has @emph{practical} browser
portability problems as a bug (@pxref{Reporting Bugs}).

A few other general points about the HTML output follow.

@cindex Navigation bar, in HTML output
@strong{Navigation bar:} By default, a navigation bar is inserted at the
start of each node, analogous to Info output.  If the
@samp{--no-headers} option is used, the navigation bar is only
inserted at the beginning of split files.  Header @code{<link>}
elements in split output can support Info-like navigation with
browsers like Lynx and @w{Emacs W3} which implement this HTML@tie{}1.0
feature.

@cindex Footnote styles, in HTML
@strong{Footnotes:} for HTML, when the footnote style is @samp{end},
or if the output is not split, footnotes are put at the end of the
output.  If the footnoet style is set to @samp{separate}, and the
output is split, they are placed in a separate file.  @xref{Footnote
Styles}.

@cindex Escaping to HTML
@cindex Raw HTML
@strong{Raw HTML}: @command{makeinfo} will include segments of Texinfo
source between @code{@@ifhtml} and @code{@@end ifhtml} in the HTML
output (but not any of the other conditionals, by default).  Source
between @code{@@html} and @code{@@end html} is passed without change
to the output (i.e., suppressing the normal escaping of input
@samp{<}, @samp{>} and @samp{&} characters which have special
significance in HTML)@.  @xref{Conditional Commands}.

@node HTML Splitting
@section HTML Splitting
@cindex Split HTML output
@cindex HTML output, split

When splitting output at nodes (which is the default),
@command{makeinfo} writes HTML output into (basically) one output file
per Texinfo source @code{@@node}.

Each output file name is the node name with spaces replaced by
@samp{-}'s and special characters changed to @samp{_} followed by
their code point in hex (@pxref{HTML Xref}).  This is to make it
portable and easy to use as a filename.  In the unusual case of two
different nodes having the same name after this treatment, they are
written consecutively to the same file, with HTML anchors so each can
be referred to independently.

If @command{makeinfo} is run on a system which does not distinguish
case in file names, nodes which are the same except for case (e.g.,
@samp{index} and @samp{Index}) will also be folded into the same
output file with anchors.  You can also pretend to be on a case
insensitive filesystem by setting the customization variable
@code{CASE_INSENSITIVE_FILENAMES}.

It is also possible to split at chapters or sections with
@option{--split} (@pxref{Invoking @command{texi2any}}).  In that case,
the file names are constructed after the name of the node associated
with the relevant sectioning command.  Also, unless
@option{--no-node-files} is specified, a redirection file is output
for every node in order to more reliably support cross-references to
that manual (@pxref{HTML Xref}).

When splitting, the HTML output files are written into a subdirectory,
with the name chosen as follows:

@enumerate
@item
@command{makeinfo} first tries the subdirectory with the base name
from @code{@@setfilename} (that is, any extension is removed).  For
example, HTML output for @code{@@setfilename gcc.info} would be
written into a subdirectory named @samp{gcc/}.

@item
If that directory cannot be created for any reason, then
@command{makeinfo} tries appending @samp{.html} to the directory name.
For example, output for @code{@@setfilename texinfo} would be written
to @samp{texinfo.html/}.

@item
If the @samp{@var{name}.html} directory can't be created either,
@code{makeinfo} gives up.

@end enumerate

@noindent In any case, the top-level output file within the directory
is always named @samp{index.html}.

Monolithic output (@code{--no-split}) is named according to
@code{@@setfilename} (with any @samp{.info} extension is replaced with
@samp{.html}), @code{--output} (the argument is used literally), or
based on the input file name as a last resort
(@pxref{@code{@@setfilename}}).

@node HTML CSS
@section HTML CSS
@cindex HTML, and CSS
@cindex CSS, and HTML output
@cindex Cascading Style Sheets, and HTML output

Cascading Style Sheets (CSS for short) is an Internet standard for
influencing the display of HTML documents: see
@uref{http://www.w3.org/Style/CSS/}.

By default, @command{makeinfo} includes a few simple CSS commands to
better implement the appearance of some Texinfo environments.  Here
are two of them, as an example:

@example
pre.display @{ font-family:inherit @}
pre.smalldisplay @{ font-family:inherit; font-size:smaller @}
@end example

A full explanation of CSS is (far) beyond this manual; please see the
reference above.  In brief, however, the above tells the web browser
to use a `smaller' font size for @code{@@smalldisplay} text, and to
use the same font as the main document for both @code{@@smalldisplay}
and @code{@@display}.  By default, the HTML @samp{<pre>} command uses
a monospaced font.

You can influence the CSS in the HTML output with two
@command{makeinfo} options: @option{--css-include=@var{file}} and
@option{--css-ref=@var{url}}.

@pindex texinfo-bright-colors.css
@cindex Visualizing Texinfo CSS
The option @option{--css-ref=@var{url}} adds to each output HTML file
a @samp{<link>} tag referencing a CSS at the given @var{url}.  This
allows using external style sheets.  You may find the file
@file{texi2html/examples/texinfo-bright-colors.css} useful for
visualizing the CSS elements in Texinfo output.

The option @option{--css-include=@var{file}} includes the contents
@var{file} in the HTML output, as you might expect.  However, the
details are somewhat tricky, as described in the following, to provide
maximum flexibility.

@cindex @samp{@@import} specifications, in CSS files
The CSS file may begin with so-called @samp{@@import} directives,
which link to external CSS specifications for browsers to use when
interpreting the document.  Again, a full description is beyond our
scope here, but we'll describe how they work syntactically, so we can
explain how @command{makeinfo} handles them.

@cindex Comments, in CSS files
There can be more than one @samp{@@import}, but they have to come
first in the file, with only whitespace and comments interspersed, no
normal definitions.  (Technical exception: a @samp{@@charset}
directive may precede the @samp{@@import}'s.  This does not alter
@command{makeinfo}'s behavior, it just copies the @samp{@@charset} if
present.)  Comments in CSS files are delimited by @samp{/* ... */}, as
in C@.  An @samp{@@import} directive must be in one of these two forms:

@example
@@import url(http://example.org/foo.css);
@@import "http://example.net/bar.css";
@end example

As far as @command{makeinfo} is concerned, the crucial characters are
the @samp{@@} at the beginning and the semicolon terminating the
directive.  When reading the CSS file, it simply copies any such
@samp{@@}-directive into the output, as follows:

@itemize
@item If @var{file} contains only normal CSS declarations, it is
included after @command{makeinfo}'s default CSS, thus overriding it.

@item If @var{file} begins with @samp{@@import} specifications (see
below), then the @samp{import}'s are included first (they have to come
first, according to the standard), and then @command{makeinfo}'s
default CSS is included.  If you need to override @command{makeinfo}'s
defaults from an @samp{@@import}, you can do so with the @samp{!@:
important} CSS construct, as in:
@example
pre.smallexample @{ font-size: inherit ! important @}
@end example

@item If @var{file} contains both @samp{@@import} and inline CSS
specifications, the @samp{@@import}'s are included first, then
@command{makeinfo}'s defaults, and lastly the inline CSS from
@var{file}.

@item Any @@-directive other than @samp{@@import} and @samp{@@charset}
is treated as a CSS declaration, meaning @command{makeinfo} includes
its default CSS and then the rest of the file.
@end itemize

If the CSS file is malformed or erroneous, @command{makeinfo}'s output
is unspecified.  @command{makeinfo} does not try to interpret the
meaning of the CSS file in any way; it just looks for the special
@samp{@@} and @samp{;} characters and blindly copies the text into the
output.  Comments in the CSS file may or may not be included in the
output.

In addition to the possibilities offered by CSS, @command{makeinfo}
has many user-definable customization variables with which you can
influence the HTML output.  @xref{Customization Variables}.

@node HTML Xref
@section HTML Cross-references
@cindex HTML cross-references
@cindex Cross-references, in HTML output

Cross-references between Texinfo manuals in HTML format become, in the
end, a standard HTML @code{<a>} link, but the details are
unfortunately complex.  This section describes the algorithm used in
detail, so that Texinfo can cooperate with other programs, such as
@command{texi2html}, by writing mutually compatible HTML files.

This algorithm may or may not be used for links @emph{within} HTML
output for a Texinfo file.  Since no issues of compatibility arise in
such cases, we do not need to specify this.

We try to support references to such ``external'' manuals in both
monolithic and split forms.  A @dfn{monolithic} (mono) manual is
entirely contained in one file, and a @dfn{split} manual has a file
for each node.  (@xref{HTML Splitting}.)

@cindex Dumas, Patrice
The algorithm was primarily devised by Patrice Dumas in 2003--04.

@menu
* Link Basics:       HTML Xref Link Basics.
* Node Expansion:    HTML Xref Node Name Expansion.
* Command Expansion: HTML Xref Command Expansion.
* 8-bit Expansion:   HTML Xref 8-bit Character Expansion.
* Mismatch:          HTML Xref Mismatch.
* Configuration:     HTML Xref Configuration. htmlxref.cnf.
* Preserving links:  HTML Xref Link Preservation. MANUAL-noderename.cnf.
@end menu

@node HTML Xref Link Basics
@subsection HTML Cross-reference Link Basics
@cindex HTML cross-reference link basics

For our purposes, an HTML link consists of four components: a host
name, a directory part, a file part, and a target part.  We
always assume the @code{http} protocol.  For example:

@example
http://@var{host}/@var{dir}/@var{file}.html#@var{target}
@end example

The information to construct a link comes from the node name and
manual name in the cross-reference command in the Texinfo source
(@pxref{Cross References}), and from @dfn{external information}
(@pxref{HTML Xref Configuration}).

We now consider each part in turn.

The @var{host} is hardwired to be the local host.  This could either
be the literal string @samp{localhost}, or, according to the rules for
HTML links, the @samp{http://localhost/} could be omitted entirely.

The @var{dir} and @var{file} parts are more complicated, and depend on
the relative split/mono nature of both the manual being processed and
the manual that the cross-reference refers to.  The underlying idea is
that there is one directory for Texinfo manuals in HTML, and a given
@var{manual} is either available as a monolithic file
@file{@var{manual}.html}, or a split subdirectory
@file{@var{manual}/*.html}.  Here are the cases:

@itemize @bullet
@item
If the present manual is split, and the referent manual is also split,
the directory is @samp{../@var{referent/}} and the file is the
expanded node name (described later).

@item
If the present manual is split, and the referent manual is mono, the
directory is @samp{../} and the file is @file{@var{referent}.html}.

@item
If the present manual is mono, and the referent manual is split, the
directory is @file{@var{referent}/} and the file is the expanded node
name.

@item
If the present manual is mono, and the referent manual is also mono,
the directory is @file{./} (or just the empty string), and the file is
@file{@var{referent}.html}.

@end itemize

@vindex BASEFILENAME_LENGTH
Another rule, that only holds for filenames, is that base filenames
are truncated to 245 characters, to allow for an extension to be
appended and still comply with the 255-character limit which is common
to many filesystems.  Although technically this can be changed with
the @code{BASEFILENAME_LENGTH} customization variable (@pxref{Other
Customization Variables}), doing so would make cross-manual references
to such nodes invalid.

Any directory part in the filename argument of the source cross
reference command is ignored.  Thus, @code{@@xref@{,,,../foo@}} and
@code{@@xref@{,,,foo@}} both use @samp{foo} as the manual name.  This
is because any such attempted hardwiring of the directory is very
unlikely to be useful for both Info and HTML output.

Finally, the @var{target} part is always the expanded node name.

Whether the present manual is split or mono is determined by user
option; @command{makeinfo} defaults to split, with the
@option{--no-split} option overriding this.

Whether the referent manual is split or mono, however, is another bit
of the external information (@pxref{HTML Xref Configuration}).  By
default, @command{makeinfo} uses the same form of the referent manual
as the present manual.

Thus, there can be a mismatch between the format of the referent
manual that the generating software assumes, and the format it's
actually present in.  @xref{HTML Xref Mismatch}.

@node HTML Xref Node Name Expansion
@subsection HTML Cross-reference Node Name Expansion
@cindex HTML cross-reference node name expansion
@cindex node name expansion, in HTML cross-references
@cindex expansion, of node names in HTML cross-references

As mentioned in the previous section, the key part of the HTML cross
reference algorithm is the conversion of node names in the Texinfo
source into strings suitable for XHTML identifiers and filenames.  The
restrictions are similar for each: plain ASCII letters, numbers, and
the @samp{-} and @samp{_} characters are all that can be used.
(Although HTML anchors can contain most characters, XHTML is more
restrictive.)

Cross-references in Texinfo can refer either to nodes or anchors
(@pxref{@code{@@anchor}}).  However, anchors are treated identically
to nodes in this context, so we'll continue to say ``node'' names for
simplicity.

A special exception: the Top node (@pxref{The Top Node}) is always
mapped to the file @file{index.html}, to match web server software.
However, the HTML @emph{target} is @samp{Top}.  Thus (in the split case):

@example
@@xref@{Top,,, emacs, The GNU Emacs Manual@}.
@result{} <a href="emacs/index.html#Top">
@end example

@enumerate
@item
The standard ASCII letters (a-z and A-Z) are not modified.  All other
characters may be changed as specified below.

@item
The standard ASCII numbers (0-9) are not modified except when a number
is the first character of the node name.  In that case, see below.

@item
Multiple consecutive space, tab and newline characters are transformed
into just one space.  (It's not possible to have newlines in node
names with the current implementation, but we specify it anyway, just
in case.)

@item
Leading and trailing spaces are removed.

@item
After the above has been applied, each remaining space character is
converted into a @samp{-} character.

@item
Other ASCII 7-bit characters are transformed into @samp{_00@var{xx}},
where @var{xx} is the ASCII character code in (lowercase) hexadecimal.
This includes @samp{_}, which is mapped to @samp{_005f}.

@item
If the node name does not begin with a letter, the literal string
@samp{g_t} is prefixed to the result.  (Due to the rules above, that
string can never occur otherwise; it is an arbitrary choice, standing
for ``GNU Texinfo''.)  This is necessary because XHTML requires that
identifiers begin with a letter.

@end enumerate

For example:

@example
@@node A  node --- with _'%
@result{} A-node-_002d_002d_002d-with-_005f_0027_0025
@end example

Example translations of common characters:

@itemize @bullet
@item @samp{_} @result{} @samp{_005f}
@item @samp{-} @result{} @samp{_002d}
@item @samp{A  node} @result{} @samp{A-node}
@end itemize

On case-folding computer systems, nodes differing only by case will be
mapped to the same file.  In particular, as mentioned above, Top
always maps to the file @file{index.html}.  Thus, on a case-folding
system, Top and a node named `Index' will both be written to
@file{index.html}.  Fortunately, the targets serve to distinguish
these cases, since HTML target names are always case-sensitive,
independent of operating system.

@node HTML Xref Command Expansion
@subsection HTML Cross-reference Command Expansion
@cindex HTML cross-reference command expansion

Node names may contain @@-commands (@pxref{Node Line Requirements}).
This section describes how they are handled.

First, comments are removed.

Next, any @code{@@value} commands (@pxref{@code{@@set @@value}}) and
macro invocations (@pxref{Invoking Macros}) are fully expanded.

Then, for the following commands, the command name and braces are removed,
and the text of the argument is recursively transformed:

@example
@@asis @@b @@cite @@code @@command @@dfn @@dmn @@dotless
@@emph @@env @@file @@i @@indicateurl @@kbd @@key
@@samp @@sansserif @@sc @@slanted @@strong @@sub @@sup
@@t @@U @@var @@verb @@w
@end example

@noindent For @code{@@sc}, any letters are capitalized.

In addition, the following commands are replaced by constant text, as
shown below.  If any of these commands have non-empty arguments, as in
@code{@@TeX@{bad@}}, it is an error, and the result is unspecified.
In this table, `(space)' means a space character and `(nothing)' means
the empty string.  The notation `U+@var{hhhh}' means Unicode code
point @var{hhhh} (in hex, as usual).

There are further transformations of many of these expansions to yield
the final file or other target name, such as space characters to
@samp{-}, etc., according to the other rules.

@multitable @columnfractions .3 .5
@item @code{@@(newline)}        @tab (space)
@item @code{@@(space)}          @tab (space)
@item @code{@@(tab)}            @tab (space)
@item @code{@@!}                @tab @samp{!}
@item @code{@@*}                @tab (space)
@item @code{@@-}                @tab (nothing)
@item @code{@@.}                @tab @samp{.}
@item @code{@@:}                @tab (nothing)
@item @code{@@?}                @tab @samp{?}
@item @code{@@@@}               @tab @samp{@@}
@item @code{@@@{}               @tab @samp{@{}
@item @code{@@@}}               @tab @samp{@}}
@item @code{@@LaTeX}            @tab @samp{LaTeX}
@item @code{@@TeX}              @tab @samp{TeX}
@item @code{@@arrow}            @tab U+2192
@item @code{@@bullet}           @tab U+2022
@item @code{@@comma}            @tab @samp{,}
@item @code{@@copyright}        @tab U+00A9
@item @code{@@dots}             @tab U+2026
@item @code{@@enddots}          @tab @samp{...}
@item @code{@@equiv}            @tab U+2261
@item @code{@@error}            @tab @samp{error-->}
@item @code{@@euro}             @tab U+20AC
@item @code{@@exclamdown}       @tab U+00A1
@item @code{@@expansion}        @tab U+21A6
@item @code{@@geq}              @tab U+2265
@item @code{@@leq}              @tab U+2264
@item @code{@@minus}            @tab U+2212
@item @code{@@ordf}             @tab U+00AA
@item @code{@@ordm}             @tab U+00BA
@item @code{@@point}            @tab U+2605
@item @code{@@pounds}           @tab U+00A3
@item @code{@@print}            @tab U+22A3
@item @code{@@questiondown}     @tab U+00BF
@item @code{@@registeredsymbol} @tab U+00AE
@item @code{@@result}           @tab U+21D2
@item @code{@@textdegree}       @tab U+00B0
@item @code{@@tie}              @tab (space)
@end multitable

Quotation mark @@-commands (@code{@@quotedblright@{@}} and the like),
are likewise replaced by their Unicode values.  Normal quotation
@emph{characters} (e.g., ASCII ` and ') are not altered.
@xref{Inserting Quotation Marks}.

Any @code{@@acronym}, @code{@@abbr}, @code{@@email}, and
@code{@@image} commands are replaced by their first argument.  (For
these commands, all subsequent arguments are optional, and ignored
here.)  @xref{@code{@@acronym}}, and @ref{@code{@@email}}, and @ref{Images}.

Accents are handled according to the next section.

Any other command is an error, and the result is unspecified.

@node HTML Xref 8-bit Character Expansion
@subsection HTML Cross-reference 8-bit Character Expansion
@cindex HTML cross-reference 8-bit character expansion
@cindex 8-bit characters, in HTML cross-references
@cindex Expansion of 8-bit characters in HTML cross-references
@cindex Transliteration of 8-bit characters in HTML cross-references

Usually, characters other than plain 7-bit ASCII are transformed into
the corresponding Unicode code point(s) in Normalization Form@tie{}C,
which uses precomposed characters where available.  (This is the
normalization form recommended by the W3C and other bodies.)  This
holds when that code point is @code{0xffff} or less, as it almost
always is.

These will then be further transformed by the rules above into the
string @samp{_@var{hhhh}}, where @var{hhhh} is the code point in hex.

For example, combining this rule and the previous section:

@example
@@node @@b@{A@} @@TeX@{@} @@u@{B@} @@point@{@}@@enddots@{@}
@result{} A-TeX-B_0306-_2605_002e_002e_002e
@end example

Notice: 1)@tie{}@code{@@enddots} expands to three periods which in
turn expands to three @samp{_002e}'s; 2)@tie{}@code{@@u@{B@}} is a `B'
with a breve accent, which does not exist as a pre-accented Unicode
character, therefore expands to @samp{B_0306} (B with combining
breve).

When the Unicode code point is above @code{0xffff}, the transformation
is @samp{__@var{xxxxxx}}, that is, two leading underscores followed by
six hex digits.  Since Unicode has declared that their highest code
point is @code{0x10ffff}, this is sufficient.  (We felt it was better
to define this extra escape than to always use six hex digits, since
the first two would nearly always be zeros.)

This method works fine if the node name consists mostly of ASCII
characters and contains only few 8-bit ones.  But if the document is
written in a language whose script is not based on the Latin alphabet
(for example, Ukrainian), it will create file names consisting almost
entirely of @samp{_@var{xxxx}} notations, which is inconvenient and
all but unreadable.  To handle such cases, @command{makeinfo} offers
the @option{--transliterate-file-names} command line option.  This
option enables @dfn{transliteration} of node names into ASCII
characters for the purposes of file name creation and referencing.
The transliteration is based on phonetic principles, which makes the
generated file names more easily understanable.

@cindex Normalization Form C, Unicode
For the definition of Unicode Normalization Form@tie{}C, see Unicode
report UAX#15, @uref{http://www.unicode.org/reports/tr15/}.  Many
related documents and implementations are available elsewhere on the
web.

@node HTML Xref Mismatch
@subsection HTML Cross-reference Mismatch
@cindex HTML cross-reference mismatch
@cindex Mismatched HTML cross-reference source and target

As mentioned earlier (@pxref{HTML Xref Link Basics}), the generating
software may need to guess whether a given manual being cross
referenced is available in split or monolithic form---and, inevitably,
it might guess wrong.  However, when the @emph{referent} manual is
generated, it is possible to handle at least some mismatches.

In the case where we assume the referent is split, but it is actually
available in mono, the only recourse would be to generate a
@file{manual/} subdirectory full of HTML files which redirect back to
the monolithic @file{manual.html}.  Since this is essentially the same
as a split manual in the first place, it's not very appealing.

On the other hand, in the case where we assume the referent is mono,
but it is actually available in split, it is possible to use
JavaScript to redirect from the putatively monolithic
@file{manual.html} to the different @file{manual/node.html} files.
Here's an example:

@example
function redirect() @{
  switch (location.hash) @{
    case "#Node1":
      location.replace("manual/Node1.html#Node1"); break;
    case "#Node2" :
      location.replace("manual/Node2.html#Node2"); break;
    @dots{}
    default:;
  @}
@}
@end example

Then, in the @code{<body>} tag of @file{manual.html}:

@example
<body onLoad="redirect();">
@end example

Once again, this is something the software which generated the
@emph{referent} manual has to do in advance, it's not something the
software generating the cross-reference in the present manual can
control.

@node HTML Xref Configuration
@subsection HTML Cross-reference Configuration: @file{htmlxref.cnf}

@pindex htmlxref.cnf
@cindex HTML cross-reference configuration
@cindex Cross-reference configuration, for HTML
@cindex Configuration, for HTML cross-manual references

@command{makeinfo} reads a file named @file{htmlxref.cnf} to gather
information for cross-references to other manuals in HTML output.  It
is looked for in the following directories:

@table @file
@item ./
(the current directory)

@item ./.texinfo/
(under the current directory)

@item ~/.texinfo/
(where @code{~} is the current user's home directory)

@item @var{sysconfdir}/texinfo/
(where @var{sysconfdir} is the system configuration directory
specified at compile-time, e.g., @file{/usr/local/etc})

@item @var{datadir}/texinfo/
(likewise specified at compile time, e.g., @file{/usr/local/share})
@end table

All files found are used, with earlier entries overriding later ones.
The Texinfo distribution includes a default file which handles many
GNU manuals; it is installed in the last of the above directories,
i.e., @file{@var{datadir}/texinfo/htmlxref.cnf}.

The file is line-oriented.  Lines consisting only of whitespace are
ignored.  Comments are indicated with a @samp{#} at the beginning of a
line, optionally preceded by whitespace.  Since @samp{#} can occur in
urls (like almost any character), it does not otherwise start a
comment.

Each non-blank non-comment line must be either a @dfn{variable
assignment} or @dfn{manual information}.

A variable assignment line looks like this:

@example
@var{varname} = @var{varvalue}
@end example

Whitespace around the @samp{=} is optional and ignored.  The
@var{varname} should consist of letters; case is significant.  The
@var{varvalue} is an arbitrary string, continuing to the end of the
line.  Variables are then referenced with @samp{$@{@var{varname}@}};
variable references can occur in the @var{varvalue}.

A manual information line looks like this:

@example
@var{manual} @var{keyword} @var{urlprefix}
@end example

@noindent
with @var{manual} the short identifier for a manual, @var{keyword}
being one of: @code{mono}, @code{node}, @code{section},
@code{chapter}, and @var{urlprefix} described below.  Variable
references can occur only in the @var{urlprefix}.  For example (used
in the canonical @file{htmlxref.cnf}):

@smallexample
G = http://www.gnu.org
GS = $@{G@}/software
hello mono    $@{GS@}/hello/manual/hello.html
hello chapter $@{GS@}/hello/manual/html_chapter/
hello section $@{GS@}/hello/manual/html_section/
hello node    $@{GS@}/hello/manual/html_node/
@end smallexample

@cindex monolithic manuals, for HTML cross-references
If the keyword is @code{mono}, @var{urlprefix} gives the host,
directory, and file name for @var{manual} as one monolithic file.

@cindex split manuals, for HTML cross-references
If the keyword is @code{node}, @code{section}, or @code{chapter},
@var{urlprefix} gives the host and directory for @var{manual} split
into nodes, sections, or chapters, respectively.

When available, @command{makeinfo} will use the ``corresponding''
value for cross-references between manuals.  That is, when generating
monolithic output (@option{--no-split}), the @code{mono} url will be
used, when generating output that is split by node, the @code{node}
url will be used, etc.  However, if a manual is not available in that
form, anything that is available can be used.  Here is the search
order for each style:

@smallexample
node    @result{} node,    section, chapter, mono
section @result{} section, chapter, node,    mono
chapter @result{} chapter, section, node,    mono
mono    @result{} mono,    chapter, section, node
@end smallexample

@opindex --node-files@r{, and HTML cross-references}
These section- and chapter-level cross-manual references can succeed
only when the target manual was created using @option{--node-files};
this is the default for split output.

If you have additions or corrections to the @file{htmlxref.cnf}
distributed with Texinfo, please email @email{bug-texinfo@@gnu.org} as
usual.  You can get the latest version from
@url{http://ftpmirror.gnu.org/@/texinfo/@/htmlxref.cnf}.

@node HTML Xref Link Preservation
@subsection HTML Cross-reference Link Preservation: @var{manual}@file{-noderename.cnf}

@pindex noderename.cnf
@pindex @var{manual}-noderename.cnf
@cindex HTML cross-reference link preservation
@cindex Preserving HTML links to old nodes
@cindex Old nodes, preserving links to
@cindex Renaming nodes, and preserving links
@cindex Links, preserving to renamed nodes
@cindex Node renaming, and preserving links

Occasionally changes in a program require removing (or renaming) nodes
in the manual in order to have the best documentation.  Given the
nature of the web, however, links may exist anywhere to such a removed
node (renaming appears the same as removal for this purpose), and it's
not ideal for those links to simply break.

@vindex RENAMED_NODES_FILE
Therefore, Texinfo provides a way for manual authors to specify old
node names and the new nodes to which the old names should be
redirected, via the file @var{manual}@file{-noderename.cnf}, where
@var{manual} is the base name of the manual.  For example, the manual
@file{texinfo.texi} would be supplemented by a file
@file{texinfo-noderename}.cnf.  (This name can be overridden by
setting the @file{RENAMED_NODES_FILE} customization variable;
@pxref{Customization Variables}).

The file is read in pairs of lines, as follows:

@example
@var{old-node-name}
@@@@@{@} @var{new-node-name}
@end example

The usual conversion from Texinfo node names to HTML names is applied;
see this entire section for details (@pxref{HTML Xref}).  The unusual
@samp{@@@@@{@}} separator is used because it is not a valid Texinfo
construct, so can't appear in the node names.

The effect is that @command{makeinfo} generates a redirect from
@var{old-node-name} to @var{new-node-name} when producing HTML output.
Thus, external links to the old node are preserved.

Lines consisting only of whitespace are ignored.  Comments are
indicated with a @samp{@@c} at the beginning of a line, optionally
preceded by whitespace.

Another approach to preserving links to deleted or renamed nodes is to
use anchors (@pxref{@code{@@anchor}}).  There is no effective
difference between the two approaches.

@node @@-Command Details
@appendix @@-Command Details

Here are the details of @@-commands: information about their syntax, a
list of commands, and information about where commands can appear.

@node Command Syntax
@section @@-Command Syntax
@cindex @@-command syntax
@cindex Syntax, of @@-commands
@cindex Command syntax

Texinfo has the following types of @@-command:

@table @asis
@item 1. Brace commands
These commands start with @@ followed by a letter or a word, followed by an
argument within braces.  For example, the command @code{@@dfn} indicates
the introductory or defining use of a term; it is used as follows: @samp{In
Texinfo, @@@@-commands are @@dfn@{mark-up@} commands.}

@item 2. Line commands
These commands occupy an entire line.  The line starts with @@,
followed by the name of the command (a word); for example, @code{@@center}
or @code{@@cindex}.  If no argument is needed, the word is followed by
the end of the line.  If there is an argument, it is separated from
the command name by a space.  Braces are not used.

@item 3. Block commands
These commands are written at the start of a line, with general text on
following lines, terminated by a matching @code{@@end} command on a
line of its own.  For example, @code{@@example}, then the lines of a
coding example, then @code{@@end example}.  Some of these block commands
take arguments as line commands do; for example, @code{@@enumerate A}
opening an environment terminated by @code{@@end enumerate}.  Here
@samp{A} is the argument.

@item 4. Symbol insertion commands with no arguments
These commands start with @@ followed by a word followed by a
left and right- brace.  These commands insert special symbols in
the document; they do not take arguments.  Some examples:
@code{@@dots@{@}} @result{} @samp{@dots{}}, @code{@@equiv@{@}}
@result{} @samp{@equiv{}}, @code{@@TeX@{@}} @result{} `@TeX{}', and
@code{@@bullet@{@}} @result{} @samp{@bullet{}}.

@item 5. Non-alphabetic commands
The names of commands in all of the above categories consist of
alphabetic characters, almost entirely in lower-case.  Unlike those, the
non-alphabetic commands commands consist of an @@ followed by a
punctuation mark or other character that is not part of the Latin
alphabet.  Non-alphabetic commands are almost always part of text
within a paragraph.  The non-alphabetic commands include @code{@@@@},
@code{@@@{}, @code{@@@}}, @code{@@.}, @code{@@@kbd{SPACE}}, and most of
the accent commands.

@item 6. Miscellaneous commands
There are a handful of commands that don't fit into any of the above
categories; for example, the obsolete command @code{@@refill}, which is
always used at the end of a paragraph immediately following the final
period or other punctuation character.  @code{@@refill} takes no
argument and does not require braces.  Likewise, @code{@@tab} used in a
@code{@@multitable} block does not take arguments, and is not followed
by braces.
@end table

@cindex Braces and argument syntax
Thus, the alphabetic commands fall into classes that have
different argument syntaxes.  You cannot tell to which class a command
belongs by the appearance of its name, but you can tell by the
command's meaning: if the command stands for a glyph, it is in
class 4 and does not require an argument; if it makes sense to use the
command among other text as part of a paragraph, the command
is in class 1 and must be followed by an argument in braces.  The
non-alphabetic commands, such as @code{@@:}, are exceptions to the
rule; they do not need braces.

The purpose of having different syntax for commands is to make Texinfo
files easier to read, and also to help the GNU Emacs paragraph and
filling commands work properly.

@node Command List
@section @@-Command List
@cindex Alphabetical @@-command list
@cindex List of @@-commands
@cindex @@-command list
@cindex Reference to @@-commands

Here is an alphabetical list of the @@-commands in Texinfo.  Square
brackets, @t{[}@w{ }@t{]}, indicate optional arguments; an ellipsis,
@samp{@dots{}}, indicates repeated text.

@table @code
@item @@@var{whitespace}
An @code{@@} followed by a space, tab, or newline produces a normal,
stretchable, interword space.  @xref{Multiple Spaces}.

@item @@!
Produce an exclamation point that ends a sentence (usually after an
end-of-sentence capital letter).  @xref{Ending a Sentence}.

@item @@"
@itemx @@'
Generate an umlaut or acute accent, respectively, over the next
character, as in @"o and @'o.  @xref{Inserting Accents}.

@item @@*
Force a line break.  @xref{Line Breaks}.

@item @@,@{@var{c}@}
Generate a cedilla accent under @var{c}, as in @,{c}.  @xref{Inserting
Accents}.

@item @@-
Insert a discretionary hyphenation point.  @xref{@code{@@- @@hyphenation}}.

@item @@.
Produce a period that ends a sentence (usually after an
end-of-sentence capital letter).  @xref{Ending a Sentence}.

@item @@/
Produces no output, but allows a line break.  @xref{Line Breaks}.

@item @@:
Tell @TeX{} to refrain from inserting extra whitespace after an
immediately preceding period, question mark, exclamation mark, or
colon, as @TeX{} normally would.  @xref{Not Ending a Sentence}.

@item @@=
Generate a macron (bar) accent over the next character, as in @=o.
@xref{Inserting Accents}.

@item @@?
Produce a question mark that ends a sentence (usually after an
end-of-sentence capital letter).  @xref{Ending a Sentence}.

@item @@@@
@itemx @@atchar@{@}
Insert an at sign, @samp{@@}.  @xref{Inserting an Atsign}.

@item @@\
@itemx @@backslashchar@{@}
Insert a backslash, @samp{\}; @code{@@backslashchar@{@}} works
anywhere, while @code{@@\} works only inside @code{@@math}.
@xref{Inserting a Backslash}, and @ref{Inserting Math}.

@item @@^
@itemx @@`
Generate a circumflex (hat) or grave accent, respectively, over the next
character, as in @^o and @`e.
@xref{Inserting Accents}.

@item @@@{
@itemx @@lbracechar@{@}
Insert a left brace, @samp{@{}.  @xref{Inserting Braces}.

@item @@@}
@itemx @@rbracechar@{@}
Insert a right brace, @samp{@}}.  @xref{Inserting Braces}.

@item @@~
Generate a tilde accent over the next character, as in @~N.
@xref{Inserting Accents}.

@item @@AA@{@}
@itemx @@aa@{@}
Generate the uppercase and lowercase Scandinavian A-ring letters,
respectively: @AA{}, @aa{}.  @xref{Inserting Accents}.

@item @@abbr@{@var{abbreviation}@}
Indicate a general abbreviation, such as `Comput.'.
@xref{@code{@@abbr}}.

@item @@acronym@{@var{acronym}@}
Indicate an acronym in all capital letters, such as `NASA'.
@xref{@code{@@acronym}}.

@item @@AE@{@}
@itemx @@ae@{@}
Generate the uppercase and lowercase AE ligatures, respectively:
@AE{}, @ae{}.  @xref{Inserting Accents}.

@item @@afivepaper
Change page dimensions for the A5 paper size.  @xref{A4 Paper}.

@item @@afourlatex
@itemx @@afourpaper
@itemx @@afourwide
Change page dimensions for the A4 paper size.  @xref{A4 Paper}.

@item @@alias @var{new}=@var{existing}
Make the command @samp{@@@var{new}} a synonym for the existing command
@samp{@@@var{existing}}.  @xref{@code{@@alias}}.

@item @@allowcodebreaks @var{true-false}
Control breaking at @samp{-} and @samp{_} in @TeX{}.
@xref{@code{@@allowcodebreaks}}.

@item @@anchor@{@var{name}@}
Define @var{name} as the current location for use as a cross-reference
target.  @xref{@code{@@anchor}}.

@item @@appendix @var{title}
Begin an appendix.  The title appears in the table of contents.  In
Info, the title is underlined with asterisks.
@xref{@code{@@unnumbered @@appendix}}.

@item @@appendixsec @var{title}
@itemx @@appendixsection @var{title}
Begin an appendix section within an appendix.  The section title
appears in the table of contents.  In Info, the title is underlined
with equal signs.  @code{@@appendixsection} is a longer spelling of
the @code{@@appendixsec} command.  @xref{@code{@@unnumberedsec
@@appendixsec @@heading}}.

@item @@appendixsubsec @var{title}
Begin an appendix subsection.  The title appears in the table of
contents.  In Info, the title is underlined with hyphens.
@xref{@code{@@unnumberedsubsec @@appendixsubsec @@subheading}}.

@item @@appendixsubsubsec @var{title}
Begin an appendix subsubsection.  The title appears in the table of
contents.  In Info, the title is underlined with periods.
@xref{@code{@@subsubsection}}.

@item @@arrow@{@}
Generate a right arrow glyph: @samp{@arrow{}}.  Used by default
for @code{@@click}.  @xref{Click Sequences}.

@item @@asis
Used following @code{@@table}, @code{@@ftable}, and @code{@@vtable} to
print the table's first column without highlighting (``as is'').
@xref{@code{@@asis}}.

@item @@author @var{author}
Typeset @var{author} flushleft and underline it.  @xref{@code{@@title
@@subtitle @@author}}.

@item @@b@{@var{text}@}
Set @var{text} in a @b{bold} font.  No effect in Info.  @xref{Fonts}.

@item @@bullet@{@}
Generate a large round dot, @bullet{} (@samp{*} in Info).  Often used
with @code{@@table}.  @xref{@code{@@bullet}}.

@item @@bye
Stop formatting a file.  The formatters do not see anything in the
input file following @code{@@bye}.  @xref{Ending a File}.

@item @@c @var{comment}
Begin a comment in Texinfo.  The rest of the line does not appear in
any output.  A synonym for @code{@@comment}.  @kbd{DEL} also
starts a comment.  @xref{Comments}.

@item @@caption
Define the full caption for a @code{@@float}.  @xref{@code{@@caption
@@shortcaption}}.

@item @@cartouche
Highlight an example or quotation by drawing a box with rounded
corners around it.  Pair with @code{@@end cartouche}.  No effect in
Info.  @xref{@code{@@cartouche}}.

@item @@center @var{line-of-text}
Center the line of text following the command.
@xref{@code{@@titlefont @@center @@sp}}.

@item @@centerchap @var{line-of-text}
Like @code{@@chapter}, but centers the chapter title.  @xref{@code{@@chapter}}.

@item @@chapheading @var{title}
Print an unnumbered chapter-like heading, but omit from the table of
contents.  In Info, the title is underlined with asterisks.
@xref{@code{@@majorheading @@chapheading}}.

@item @@chapter @var{title}
Begin a numbered chapter.  The chapter title appears in the table of
contents.  In Info, the title is underlined with asterisks.
@xref{@code{@@chapter}}.

@item @@cindex @var{entry}
Add @var{entry} to the index of concepts.  @xref{Index Entries, ,
Defining the Entries of an Index}.

@item @@cite@{@var{reference}@}
Highlight the name of a book or other reference that has no companion
Info file.  @xref{@code{@@cite}}.

@item @@clear @var{flag}
Unset @var{flag}, preventing the Texinfo formatting commands from
formatting text between subsequent pairs of @code{@@ifset @var{flag}}
and @code{@@end ifset} commands, and preventing
@code{@@value@{@var{flag}@}} from expanding to the value to which
@var{flag} is set.  @xref{@code{@@set @@clear @@value}}.

@item @@click@{@}
Represent a single ``click'' in a GUI@.  Used within
@code{@@clicksequence}.  @xref{Click Sequences}.

@item @@clicksequence@{@var{action} @@click@{@} @var{action}@}
Represent a sequence of clicks in a GUI@.  @xref{Click Sequences}.

@item @@clickstyle @@@var{cmd}
Execute @@@var{cmd} for each @code{@@click}; the default is
@code{@@arrow}.  The usual following empty braces on @@@var{cmd} are
omitted.  @xref{Click Sequences}.

@item @@code@{@var{sample-code}@}
Indicate an expression, a syntactically complete token of a program,
or a program name.  Unquoted in Info output.  @xref{@code{@@code}}.

@item @@codequotebacktick @var{on-off}
@itemx @@codequoteundirected @var{on-off}
Control output of @code{`} and @code{'} in code examples.
@xref{Inserting Quote Characters}.

@item @@comma@{@}
Insert a comma `,' character; only needed when a literal comma would
be taken as an argument separator.  @xref{Inserting a Comma}.

@item @@command@{@var{command-name}@}
Indicate a command name, such as @command{ls}.  @xref{@code{@@command}}.

@item @@comment @var{comment}
Begin a comment in Texinfo.  The rest of the line does not appear in
any output.  A synonym for @code{@@c}.
@xref{Comments}.

@item @@contents
Print a complete table of contents.  Has no effect in Info, which uses
menus instead.  @xref{Contents, , Generating a Table of Contents}.

@item @@copying
Specify copyright holders and copying conditions for the document.  Pair
with @code{@@end copying}.  @xref{@code{@@copying}}.

@item @@copyright@{@}
Generate the copyright symbol @copyright{}.
@xref{@code{@@copyright}}.

@item @@defcodeindex @var{index-name}
Define a new index and its indexing command.  Print entries in an
@code{@@code} font.  @xref{New Indices, , Defining New Indices}.

@item @@defcv @var{category} @var{class} @var{name}
@itemx @@defcvx @var{category} @var{class} @var{name}
Format a description for a variable associated with a class in
object-oriented programming.  Takes three arguments: the category of
thing being defined, the class to which it belongs, and its name.
@xref{Definition Commands}.

@item @@deffn @var{category} @var{name} @var{arguments}@dots{}
@itemx @@deffnx @var{category} @var{name} @var{arguments}@dots{}
Format a description for a function, interactive command, or similar
entity that may take arguments.  @code{@@deffn} takes as arguments the
category of entity being described, the name of this particular
entity, and its arguments, if any.  @xref{Definition Commands}.

@item @@defindex @var{index-name}
Define a new index and its indexing command.  Print entries in a roman
font.  @xref{New Indices, , Defining New Indices}.

@item @@definfoenclose @var{newcmd}, @var{before}, @var{after}
Must be used within @code{@@ifinfo}; create a new command
@code{@@@var{newcmd}} for Info that marks text by enclosing it in
strings that precede and follow the text.
@xref{@code{@@definfoenclose}}.

@item @@defivar @var{class} @var{instance-variable-name}
@itemx @@defivarx @var{class} @var{instance-variable-name}
Format a description for an instance variable in object-oriented
programming.  The command is equivalent to @samp{@@defcv @{Instance
Variable@} @dots{}}.  @xref{Definition Commands}.

@item @@defmac @var{macroname} @var{arguments}@dots{}
@itemx @@defmacx @var{macroname} @var{arguments}@dots{}
Format a description for a macro; equivalent to @samp{@@deffn Macro
@dots{}}.  @xref{Definition Commands}.

@item @@defmethod @var{class} @var{method-name} @var{arguments}@dots{}
@itemx @@defmethodx @var{class} @var{method-name} @var{arguments}@dots{}
Format a description for a method in object-oriented programming;
equivalent to @samp{@@defop Method @dots{}}.  @xref{Definition
Commands}.

@item @@defop @var{category} @var{class} @var{name} @var{arguments}@dots{}
@itemx @@defopx @var{category} @var{class} @var{name} @var{arguments}@dots{}
Format a description for an operation in object-oriented programming.
@code{@@defop} takes as arguments the name of the category of
operation, the name of the operation's class, the name of the
operation, and its arguments, if any.  @xref{Definition Commands}, and
@ref{Abstract Objects}.

@item @@defopt @var{option-name}
@itemx @@defoptx @var{option-name}
Format a description for a user option; equivalent to @samp{@@defvr
@{User Option@} @dots{}}.  @xref{Definition Commands}.

@item @@defspec @var{special-form-name} @var{arguments}@dots{}
@itemx @@defspecx @var{special-form-name} @var{arguments}@dots{}
Format a description for a special form; equivalent to @samp{@@deffn
@{Special Form@} @dots{}}.  @xref{Definition Commands}.

@item @@deftp @var{category} @var{name-of-type} @var{attributes}@dots{}
@itemx @@deftpx @var{category} @var{name-of-type} @var{attributes}@dots{}
Format a description for a data type; its arguments are the category,
the name of the type (e.g., @samp{int}) , and then the names of
attributes of objects of that type.  @xref{Definition Commands}, and
@ref{Data Types}.

@item @@deftypecv @var{category} @var{class} @var{data-type} @var{name}
@itemx @@deftypecvx @var{category} @var{class} @var{data-type} @var{name}
Format a description for a typed class variable in object-oriented programming.
@xref{Definition Commands}, and @ref{Abstract Objects}.

@item @@deftypefn @var{category} @var{data-type} @var{name} @var{arguments}@dots{}
@itemx @@deftypefnx @var{category} @var{data-type} @var{name} @var{arguments}@dots{}
Format a description for a function or similar entity that may take
arguments and that is typed.  @code{@@deftypefn} takes as arguments the
category of entity being described, the type, the name of the
entity, and its arguments, if any.  @xref{Definition Commands}.

@item @@deftypefnnewline @var{on-off}
Specifies whether return types for @code{@@deftypefn} and similar are
printed on lines by themselves; default is off.  @xref{Typed
Functions,, Functions in Typed Languages}.

@item @@deftypefun @var{data-type} @var{function-name} @var{arguments}@dots{}
@itemx @@deftypefunx @var{data-type} @var{function-name} @var{arguments}@dots{}
Format a description for a function in a typed language.
The command is equivalent to @samp{@@deftypefn Function @dots{}}.
@xref{Definition Commands}.

@item @@deftypeivar @var{class} @var{data-type} @var{variable-name}
@itemx @@deftypeivarx @var{class} @var{data-type} @var{variable-name}
Format a description for a typed instance variable in object-oriented
programming. @xref{Definition Commands}, and @ref{Abstract Objects}.

@item @@deftypemethod @var{class} @var{data-type} @var{method-name} @var{arguments}@dots{}
@itemx @@deftypemethodx @var{class} @var{data-type} @var{method-name} @var{arguments}@dots{}
Format a description for a typed method in object-oriented programming.
@xref{Definition Commands}.

@item @@deftypeop @var{category} @var{class} @var{data-type} @var{name} @var{arguments}@dots{}
@itemx @@deftypeopx @var{category} @var{class} @var{data-type} @var{name} @var{arguments}@dots{}
Format a description for a typed operation in object-oriented programming.
@xref{Definition Commands}, and @ref{Abstract Objects}.

@item @@deftypevar @var{data-type} @var{variable-name}
@itemx @@deftypevarx @var{data-type} @var{variable-name}
Format a description for a variable in a typed language.  The command is
equivalent to @samp{@@deftypevr Variable @dots{}}.  @xref{Definition
Commands}.

@item @@deftypevr @var{category} @var{data-type} @var{name}
@itemx @@deftypevrx @var{category} @var{data-type} @var{name}
Format a description for something like a variable in a typed
language---an entity that records a value.  Takes as arguments the
category of entity being described, the type, and the name of the
entity.  @xref{Definition Commands}.

@item @@defun @var{function-name} @var{arguments}@dots{}
@itemx @@defunx @var{function-name} @var{arguments}@dots{}
Format a description for a function; equivalent to
@samp{@@deffn Function @dots{}}.  @xref{Definition Commands}.

@item @@defvar @var{variable-name}
@itemx @@defvarx @var{variable-name}
Format a description for a variable; equivalent to @samp{@@defvr
Variable @dots{}}.  @xref{Definition Commands}.

@item @@defvr @var{category} @var{name}
@itemx @@defvrx @var{category} @var{name}
Format a description for any kind of variable.  @code{@@defvr} takes
as arguments the category of the entity and the name of the entity.
@xref{Definition Commands}.

@item @@detailmenu
Mark the (optional) detailed node listing in a master menu.
@xref{Master Menu Parts}.

@item @@dfn@{@var{term}@}
Indicate the introductory or defining use of a term.  @xref{@code{@@dfn}}.

@item @@DH@{@}
@itemx @@dh@{@}
Generate the uppercase and lowercase Icelandic letter eth, respectively:
@DH{}, @dh{}.  @xref{Inserting Accents}.

@item @@dircategory @var{dirpart}
Specify a part of the Info directory menu where this file's entry should
go.  @xref{Installing Dir Entries}.

@item @@direntry
Begin the Info directory menu entry for this file.  Pair with
@code{@@end direntry}.  @xref{Installing Dir Entries}.

@item @@display
Begin a kind of example.  Like @code{@@example} (indent text, do not
fill), but do not select a new font.  Pair with @code{@@end display}.
@xref{@code{@@display}}.

@item @@dmn@{@var{dimension}@}
Format a unit of measure, as in 12@dmn{pt}.  Causes @TeX{} to insert a
thin space before @var{dimension}.  No effect in Info.
@xref{@code{@@dmn}}.

@item @@docbook
Enter Docbook completely.  Pair with @code{@@end docbook}.  @xref{Raw
Formatter Commands}.

@item @@documentdescription
Set the document description text, included in the HTML output.  Pair
with @code{@@end documentdescription}.  @xref{@code{@@documentdescription}}.

@item @@documentencoding @var{enc}
Declare the input encoding to be @var{enc}.
@xref{@code{@@documentencoding}}.

@item @@documentlanguage @var{CC}
Declare the document language as the two-character ISO-639 abbreviation
@var{CC}.  @xref{@code{@@documentlanguage}}.

@item @@dotaccent@{@var{c}@}
Generate a dot accent over the character @var{c}, as in @dotaccent{o}.
@xref{Inserting Accents}.

@item @@dotless@{@var{i-or-j}@}
Generate dotless i (`@dotless{i}') and dotless j (`@dotless{j}').
@xref{Inserting Accents}.

@item @@dots@{@}
Generate an ellipsis, @samp{@dots{}}.
@xref{@code{@@dots}}.

@item @@email@{@var{address}[, @var{displayed-text}]@}
Indicate an electronic mail address.  @xref{@code{@@email}}.

@item @@emph@{@var{text}@}
Emphasize @var{text}, by using @emph{italics} where possible, and
enclosing in asterisks in Info.  @xref{Emphasis, , Emphasizing Text}.

@item @@end @var{environment}
Ends @var{environment}, as in @samp{@@end example}.  @xref{Formatting
Commands,,@@-commands}.

@item @@enddots@{@}
Generate an end-of-sentence ellipsis, like this: @enddots{}
@xref{@code{@@dots}}.

@item @@enumerate [@var{number-or-letter}]
Begin a numbered list, using @code{@@item} for each entry.
Optionally, start list with @var{number-or-letter}.  Pair with
@code{@@end enumerate}.  @xref{@code{@@enumerate}}.

@item @@env@{@var{environment-variable}@}
Indicate an environment variable name, such as @env{PATH}.
@xref{@code{@@env}}.

@item @@equiv@{@}
Indicate to the reader the exact equivalence of two forms with a
glyph: @samp{@equiv{}}.  @xref{@code{@@equiv}}.

@item @@error@{@}
Indicate to the reader with a glyph that the following text is
an error message: @samp{@error{}}.  @xref{@code{@@error}}.

@item @@errormsg@{@var{msg}@}
Report @var{msg} as an error to standard error, and exit unsuccessfully.
Texinfo commands within @var{msg} are expanded to plain text.
@xref{Conditionals}, and @ref{External Macro Processors}.

@item @@euro@{@}
Generate the Euro currency sign.  @xref{@code{@@euro}}.

@item @@evenfooting [@var{left}] @@| [@var{center}] @@| [@var{right}]
@itemx @@evenheading [@var{left}] @@| [@var{center}] @@| [@var{right}]
Specify page footings resp.@: headings for even-numbered (left-hand)
pages.  @xref{Custom Headings, ,
How to Make Your Own Headings}.

@item @@everyfooting [@var{left}] @@| [@var{center}] @@| [@var{right}]
@itemx @@everyheading [@var{left}] @@| [@var{center}] @@| [@var{right}]
Specify page footings resp.@: headings for every page.  Not relevant to
Info.  @xref{Custom Headings, , How to Make Your Own Headings}.

@item @@example
Begin an example.  Indent text, do not fill, and select fixed-width
font.  Pair with @code{@@end example}.  @xref{@code{@@example}}.

@item @@exampleindent @var{indent}
Indent example-like environments by @var{indent} number of spaces
(perhaps 0).  @xref{@code{@@exampleindent}}.

@item @@exclamdown@{@}
Generate an upside-down exclamation point.  @xref{Inserting Accents}.

@item @@exdent @var{line-of-text}
Remove any indentation a line might have.  @xref{@code{@@exdent}}.

@item @@expansion@{@}
Indicate the result of a macro expansion to the reader with a special
glyph: @samp{@expansion{}}.  @xref{@code{@@expansion}}.

@item @@file@{@var{filename}@}
Highlight the name of a file, buffer, node, directory, etc.
@xref{@code{@@file}}.

@item @@finalout
Prevent @TeX{} from printing large black warning rectangles beside
over-wide lines.  @xref{Overfull hboxes}.

@item @@findex @var{entry}
Add @var{entry} to the index of functions.  @xref{Index Entries, ,
Defining the Entries of an Index}.

@item @@firstparagraphindent @var{word}
Control indentation of the first paragraph after section headers
according to @var{word}, one of `none' or `insert'.
@xref{@code{@@firstparagraphindent}}.

@item @@float
Environment to define floating material.  Pair with @code{@@end float}.
@xref{Floats}.

@item @@flushleft
@itemx @@flushright
Do not fill text; left (right) justify every line while leaving the
right (left) end ragged.  Leave font as is.  Pair with @code{@@end
flushleft} (@code{@@end flushright}).  @xref{@code{@@flushleft
@@flushright}}.

@item @@fonttextsize @var{10-11}
Change the size of the main body font in the @TeX{} output.
@xref{Fonts}.

@item @@footnote@{@var{text-of-footnote}@}
Enter a footnote.  Footnote text is printed at the bottom of the page
by @TeX{}; Info may format in either `End' node or `Separate' node style.
@xref{Footnotes}.

@item @@footnotestyle @var{style}
Specify an Info file's footnote style, either @samp{end} for the end
node style or @samp{separate} for the separate node style.
@xref{Footnotes}.

@item @@format
Begin a kind of example.  Like @code{@@display}, but do not indent.
Pair with @code{@@end format}.  @xref{@code{@@example}}.

@item @@frenchspacing @var{on-off}
Control spacing after punctuation.  @xref{@code{@@frenchspacing}}.

@item @@ftable @var{formatting-command}
Begin a two-column table, using @code{@@item} for each entry.
Automatically enter each of the items in the first column into the
index of functions.  Pair with @code{@@end ftable}.  The same as
@code{@@table}, except for indexing.  @xref{@code{@@ftable @@vtable}}.

@item @@geq@{@}
Generate a greater-than-or-equal sign, `@geq{}'.  @xref{@code{@@geq @@leq}}.

@item @@group
Disallow page breaks within following text.  Pair with @code{@@end
group}.  Ignored in Info.  @xref{@code{@@group}}.

@item @@guillemetleft@{@}
@itemx @@guillemetright@{@}
@item @@guillemotleft@{@}
@itemx @@guillemotright@{@}
@itemx @@guilsinglleft@{@}
@itemx @@guilsinglright@{@}
Double and single angle quotation marks: @guillemetleft{}
@guillemetright{} @guilsinglleft{} @guilsinglright{}.
@code{@@guillemotleft} and @code{@@guillemotright} are synonyms for
@code{@@guillemetleft} and @code{@@guillemetright}.  @xref{Inserting
Quotation Marks}.

@item @@H@{@var{c}@}
Generate the long Hungarian umlaut accent over @var{c}, as in @H{o}.

@item @@hashchar@{@}
Insert a hash `#' character; only needed when a literal hash would
introduce @code{#line} directive.  @xref{Inserting a Hashsign}, and
@ref{External Macro Processors}.

@item @@heading @var{title}
Print an unnumbered section-like heading, but omit from the table of
contents.  In Info, the title is underlined with equal signs.
@xref{@code{@@unnumberedsec @@appendixsec @@heading}}.

@item @@headings @var{on-off-single-double}
Turn page headings on or off, and/or specify single-sided or double-sided
page headings for printing.  @xref{@code{@@headings}}.

@item @@headitem
Begin a heading row in a multitable.  @xref{Multitable Rows}.

@item @@headitemfont@{@var{text}@}
Set @var{text} in the font used for multitable heading rows; mostly
useful in multitable templates.  @xref{Multitable Rows}.

@item @@html
Enter HTML completely.  Pair with @code{@@end html}.  @xref{Raw
Formatter Commands}.

@item @@hyphenation@{@var{hy-phen-a-ted words}@}
Explicitly define hyphenation points.  @xref{@code{@@- @@hyphenation}}.

@item @@i@{@var{text}@}
Set @var{text} in an @i{italic} font.  No effect in Info.  @xref{Fonts}.

@item @@ifclear @var{txivar}
If the Texinfo variable @var{txivar} is not set, format the following
text.  Pair with @code{@@end ifclear}.  @xref{@code{@@set @@clear
@@value}}.

@item @@ifcommanddefined @var{txicmd}
@itemx @@ifcommandnotdefined @var{txicmd}
If the Texinfo code @samp{@@@var{txicmd}} is (not) defined, format the
follow text.  Pair with the corresponding @code{@@end ifcommand...}.
@xref{Testing for Texinfo Commands}.

@item @@ifdocbook
@itemx @@ifhtml
@itemx @@ifinfo
Begin text that will appear only in the given output format.
@code{@@ifinfo} output appears in both Info and (for historical
compatibility) plain text output.  Pair with @code{@@end ifdocbook}
resp.@: @code{@@end ifhtml} resp.@: @code{@@end ifinfo}.
@xref{Conditionals}.

@item @@ifnotdocbook
@itemx @@ifnothtml
@itemx @@ifnotplaintext
@itemx @@ifnottex
@itemx @@ifnotxml
Begin text to be ignored in one output format but not the others.
@code{@@ifnothtml} text is omitted from HTML output, etc.  Pair with
the corresponding @code{@@end ifnot@var{format}}.
@xref{Conditionals}.

@item @@ifnotinfo
Begin text to appear in output other than Info and (for historical
compatibility) plain text.  Pair with @code{@@end ifnotinfo}.
@xref{Conditionals}.

@item @@ifplaintext
Begin text that will appear only in the plain text output.
Pair with @code{@@end ifplaintext}.  @xref{Conditionals}.

@item @@ifset @var{txivar}
If the Texinfo variable @var{txivar} is set, format the following
text.  Pair with @code{@@end ifset}.  @xref{@code{@@set @@clear
@@value}}.

@item @@iftex
Begin text to appear only in the @TeX{} output.  Pair with @code{@@end
iftex}.  @xref{Conditionals, , Conditionally Visible Text}.

@item @@ifxml
Begin text that will appear only in the XML output.  Pair with
@code{@@end ifxml}.  @xref{Conditionals}.

@item @@ignore
Begin text that will not appear in any output.  Pair with @code{@@end
ignore}.  @xref{Comments, , Comments and Ignored Text}.

@item @@image@{@var{filename}, [@var{width}], [@var{height}], [@var{alt}], [@var{ext}]@}
Include graphics image in external @var{filename} scaled to the given
@var{width} and/or @var{height}, using @var{alt} text and looking for
@samp{@var{filename}.@var{ext}} in HTML@.  @xref{Images}.

@item @@include @var{filename}
Read the contents of Texinfo source file @var{filename}.  @xref{Include Files}.

@item @@indent
Insert paragraph indentation.  @xref{@code{@@indent}}.

@item @@indentedblock
Indent a block of arbitary text on the left.  Pair with @code{@@end
indentedblock}.  @xref{@code{@@indentedblock}}.

@item @@indicateurl@{@var{indicateurl}@}
Indicate text that is a uniform resource locator for the World Wide
Web.  @xref{@code{@@indicateurl}}.

@item @@inforef@{@var{node-name}, [@var{entry-name}], @var{info-file-name}@}
Make a cross-reference to an Info file for which there is no printed
manual.  @xref{@code{@@inforef}}.

@item @@inlinefmt@{@var{fmt}, @var{text}@}
Insert @var{text} only if the output format is @var{fmt}.
@xref{Inline Conditionals}.

@item @@inlinefmtifelse@{@var{fmt}, @var{text}, @var{else-text}@}
Insert @var{text} if the output format is @var{fmt}, else @var{else-text}.

@item @@inlineifclear@{@var{var}, @var{text}@}
@itemx @@inlineifset@{@var{var}, @var{text}@}
Insert @var{text} only if the Texinfo variable @var{var} is (not) set.

@item @@inlineraw@{@var{fmt}, @var{raw-text}@}
Insert @var{text} as in a raw conditional, only if the output format
is @var{fmt}.

@item \input @var{macro-definitions-file}
Use the specified macro definitions file.  This command is used only
in the first line of a Texinfo file to cause @TeX{} to make use of the
@file{texinfo} macro definitions file.  The @code{\} in @code{\input}
is used instead of an @code{@@} because @TeX{} does not recognize
@code{@@} until after it has read the definitions file.  @xref{Texinfo
File Header}.

@item @@insertcopying
Insert the text previously defined with the @code{@@copying}
environment.  @xref{@code{@@insertcopying}}.

@item @@item
Indicate the beginning of a marked paragraph for @code{@@itemize} and
@code{@@enumerate}; indicate the beginning of the text of a first column
entry for @code{@@table}, @code{@@ftable}, and @code{@@vtable}.
@xref{Lists and Tables}.

@item @@itemize @var{mark-generating-character-or-command}
Begin an unordered list: indented paragraphs with a mark, such as
@code{@@bullet}, inside the left margin at the beginning of each item.
Pair with @code{@@end itemize}.  @xref{@code{@@itemize}}.

@item @@itemx
Like @code{@@item} but do not generate extra vertical space above the
item text.  Thus, when several items have the same description, use
@code{@@item} for the first and @code{@@itemx} for the others.
@xref{@code{@@itemx}}.

@item @@kbd@{@var{keyboard-characters}@}
Indicate characters of input to be typed by users.  @xref{@code{@@kbd}}.

@item @@kbdinputstyle @var{style}
Specify when @code{@@kbd} should use a font distinct from
@code{@@code} according to @var{style}: @code{code}, @code{distinct},
@code{example}.  @xref{@code{@@kbd}}.

@item @@key@{@var{key-name}@}
Indicate the name of a key on a keyboard.  @xref{@code{@@key}}.

@item @@kindex @var{entry}
Add @var{entry} to the index of keys.
@xref{Index Entries, , Defining the Entries of an Index}.

@item @@L@{@}
@itemx @@l@{@}
Generate the uppercase and lowercase Polish suppressed-L letters,
respectively: @L{}, @l{}.

@item @@LaTeX@{@}
Generate the @LaTeX{} logo.  @xref{@code{@@TeX @@LaTeX}}.

@item @@leq@{@}
Generate a less-than-or-equal sign, `@leq{}'.  @xref{@code{@@geq @@leq}}.

@item @@lisp
Begin an example of Lisp code.  Indent text, do not fill, and select
fixed-width font.  Pair with @code{@@end lisp}.  @xref{@code{@@lisp}}.

@item @@listoffloats
Produce a table-of-contents-like listing of @code{@@float}s.
@xref{@code{@@listoffloats}}.

@item @@lowersections
Change subsequent chapters to sections, sections to subsections, and so
on. @xref{Raise/lower sections, , @code{@@raisesections} and
@code{@@lowersections}}.

@item @@macro @var{macroname} @{@var{params}@}
Define a new Texinfo command @code{@@@var{macroname}@{@var{params}@}}.
Pair with @code{@@end macro}.  @xref{Defining Macros}.

@item @@majorheading @var{title}
Print an unnumbered chapter-like heading, but omit from the table of
contents.  This generates more vertical whitespace before the heading
than the @code{@@chapheading} command.  @xref{@code{@@majorheading
@@chapheading}}.

@item @@math@{@var{mathematical-expression}@}
Format a mathematical expression.  @xref{Inserting Math}.

@item @@menu
Mark the beginning of a menu of nodes.  No effect in a printed manual.
Pair with @code{@@end menu}.  @xref{Menus}.

@item @@minus@{@}
Generate a minus sign, `@minus{}'.  @xref{@code{@@minus}}.

@item @@multitable @var{column-width-spec}
Begin a multi-column table.  Begin each row with @code{@@item} or
@code{@@headitem}, and separate columns with @code{@@tab}.  Pair with
@code{@@end multitable}.  @xref{Multitable Column Widths}.

@item @@need @var{n}
Start a new page in a printed manual if fewer than @var{n} mils
(thousandths of an inch) remain on the current page.
@xref{@code{@@need}}.

@item @@node @var{name}, @var{next}, @var{previous}, @var{up}
Begin a new node.  @xref{Writing a Node}.

@item @@noindent
Prevent text from being indented as if it were a new paragraph.
@xref{@code{@@noindent}}.

@item @@novalidate
Suppress validation of node references and omit creation of auxiliary
files with @TeX{}.  Use before any sectioning or cross-reference
commands.  @xref{Pointer Validation}.

@item @@O@{@}
@itemx @@o@{@}
Generate the uppercase and lowercase O-with-slash letters, respectively:
@O{}, @o{}.

@item  @@oddfooting [@var{left}] @@| [@var{center}] @@| [@var{right}]
@itemx @@oddheading [@var{left}] @@| [@var{center}] @@| [@var{right}]
Specify page footings resp.@: headings for odd-numbered (right-hand)
pages.  @xref{Custom Headings, ,
How to Make Your Own Headings}.

@item @@OE@{@}
@itemx @@oe@{@}
Generate the uppercase and lowercase OE ligatures, respectively:
@OE{}, @oe{}.  @xref{Inserting Accents}.

@item @@ogonek@{@var{c}@}
Generate an ogonek diacritic under the next character, as in
@ogonek{a}.  @xref{Inserting Accents}.

@item @@option@{@var{option-name}@}
Indicate a command-line option, such as @option{-l} or
@option{--help}.  @xref{@code{@@option}}.

@item @@ordf@{@}
@itemx @@ordm@{@}
Generate the feminine and masculine Spanish ordinals, respectively:
@ordf{}, @ordm{}.  @xref{Inserting Accents}.

@item @@page
Start a new page in a printed manual.  No effect in Info.
@xref{@code{@@page}}.

@item @@pagesizes [@var{width}][, @var{height}]
Change page dimensions.  @xref{pagesizes}.

@item @@paragraphindent @var{indent}
Indent paragraphs by @var{indent} number of spaces (perhaps 0); preserve
source file indentation if @var{indent} is @code{asis}.
@xref{@code{@@paragraphindent}}.

@item @@part @var{title}
Begin a group of chapters or appendixes; included in the tables of
contents and produces a page of its own in printed output.
@xref{@code{@@part}}.

@item @@pindex @var{entry}
Add @var{entry} to the index of programs.  @xref{Index Entries, , Defining
the Entries of an Index}.

@item @@point@{@}
Indicate the position of point in a buffer to the reader with a glyph:
@samp{@point{}}.  @xref{@code{@@point}}.

@item @@pounds@{@}
Generate the pounds sterling currency sign.
@xref{@code{@@pounds}}.

@item @@print@{@}
Indicate printed output to the reader with a glyph: @samp{@print{}}.
@xref{@code{@@print}}.

@item @@printindex @var{index-name}
Generate the alphabetized index for @var{index-name} (using two
columns in a printed manual).  @xref{Printing Indices & Menus}.

@item @@pxref@{@var{node}, [@var{entry}], [@var{node-title}], [@var{info-file}], [@var{manual}]@}
Make a reference that starts with a lowercase `see' in a printed
manual.  Use within parentheses only.  Only the first argument is
mandatory.  @xref{@code{@@pxref}}.

@item @@questiondown@{@}
Generate an upside-down question mark.  @xref{Inserting Accents}.

@item @@quotation
Narrow the margins to indicate text that is quoted from another work.
Takes optional argument specifying prefix text, e.g., an author name.
Pair with @code{@@end quotation}.  @xref{@code{@@quotation}}.

@item @@quotedblleft@{@}
@itemx @@quotedblright@{@}
@itemx @@quoteleft@{@}
@itemx @@quoteright@{@}
@itemx @@quotedblbase@{@}
@itemx @@quotesinglbase@{@}
Produce various quotation marks: @quotedblleft{} @quotedblright{}
@quoteleft{} @quoteright{} @quotedblbase{} @quotesinglbase{}.
@xref{Inserting Quotation Marks}.

@item @@r@{@var{text}@}
Set @var{text} in the regular @r{roman} font.  No effect in Info.
@xref{Fonts}.

@item @@raggedright
Fill text; left justify every line while leaving the right end ragged.
Leave font as is.  Pair with @code{@@end raggedright}.  No effect in
Info.  @xref{@code{@@raggedright}}.

@item @@raisesections
Change subsequent sections to chapters, subsections to sections, and so
on.  @xref{Raise/lower sections}.

@item @@ref@{@var{node}, [@var{entry}], [@var{node-title}], [@var{info-file}], [@var{manual}]@}
Make a plain reference that does not start with any special text.
Follow command with a punctuation mark.  Only the first argument is
mandatory.  @xref{@code{@@ref}}.

@item @@refill
@findex refill
This command used to refill and indent the paragraph after all the
other processing has been done.  It is no longer needed, since all
formatters now automatically refill as needed, but you may still see
it in the source to some manuals, as it does no harm.

@item @@registeredsymbol@{@}
Generate the legal symbol @registeredsymbol{}.
@xref{@code{@@registeredsymbol}}.

@item @@result@{@}
Indicate the result of an expression to the reader with a special
glyph: @samp{@result{}}.  @xref{@code{@@result}}.

@item @@ringaccent@{@var{c}@}
Generate a ring accent over the next character, as in @ringaccent{o}.
@xref{Inserting Accents}.

@item @@samp@{@var{text}@}
Indicate a literal example of a sequence of characters, in general.
Quoted in Info output.  @xref{@code{@@samp}}.

@item @@sansserif@{@var{text}@}
Set @var{text} in a @sansserif{sans serif} font if possible.  No
effect in Info.  @xref{Fonts}.

@item @@sc@{@var{text}@}
Set @var{text} in a small caps font in printed output, and uppercase
in Info.  @xref{Smallcaps}.

@item @@section @var{title}
Begin a section within a chapter.  The section title appears in the
table of contents.  In Info, the title is underlined with equal signs.
Within @code{@@chapter} and @code{@@appendix}, the section title is
numbered; within @code{@@unnumbered}, the section is unnumbered.
@xref{@code{@@section}}.

@item @@set @var{txivar} [@var{string}]
Define the Texinfo variable @var{txivar}, optionally to the value
@var{string}.  @xref{@code{@@set @@clear @@value}}.

@item @@setchapternewpage @var{on-off-odd}
Specify whether chapters start on new pages, and if so, whether on
odd-numbered (right-hand) new pages.  @xref{@code{@@setchapternewpage}}.

@item @@setfilename @var{info-file-name}
Provide a name to be used for the output files.  This command is ignored
for @TeX{} formatting.  @xref{@code{@@setfilename}}.

@item @@settitle @var{title}
Specify the title for page headers in a printed manual, and the
default document title for HTML @samp{<head>}.
@xref{@code{@@settitle}}.

@item @@shortcaption
Define the short caption for a @code{@@float}.  @xref{@code{@@caption
@@shortcaption}}.

@item @@shortcontents
Print a short table of contents, with chapter-level entries only.  Not
relevant to Info, which uses menus rather than tables of contents.
@xref{Contents, , Generating a Table of Contents}.

@item @@shorttitlepage @var{title}
Generate a minimal title page.  @xref{@code{@@titlepage}}.

@item @@slanted@{@var{text}@}
Set @var{text} in a @slanted{slanted} font if possible.  No effect
in Info.  @xref{Fonts}.

@item @@smallbook
Cause @TeX{} to produce a printed manual in a 7 by 9.25 inch format
rather than the regular 8.5 by 11 inch format.
@xref{@code{@@smallbook}}.  Also, see @ref{@code{@@small@dots{}}}.

@item @@smalldisplay
Begin a kind of example.  Like @code{@@display}, but use a smaller
font size where possible.  Pair with @code{@@end smalldisplay}.
@xref{@code{@@small@dots{}}}.

@item @@smallexample
Begin an example.  Like @code{@@example}, but use a smaller font size
where possible.  Pair with @code{@@end smallexample}.
@xref{@code{@@small@dots{}}}.

@item @@smallformat
Begin a kind of example.  Like @code{@@format}, but use a smaller font
size where possible.  Pair with @code{@@end smallformat}.
@xref{@code{@@small@dots{}}}.

@item @@smallindentedblock
Like @code{@@indentedblock}, but use a smaller font size where
possible.  Pair with @code{@@end smallindentedblock}.
@xref{@code{@@small@dots{}}}.

@item @@smalllisp
Begin an example of Lisp code.  Same as @code{@@smallexample}.  Pair
with @code{@@end smalllisp}.  @xref{@code{@@small@dots{}}}.

@item @@smallquotation
Like @code{@@quotation}, but use a smaller font size where possible.
Pair with @code{@@end smallquotation}.  @xref{@code{@@small@dots{}}}.

@item @@sortas @{@var{key}@}
Used in the arguments to index commands to give a string by which the
index entry should be sorted.  @xref{Indexing Commands}.

@item @@sp @var{n}
Skip @var{n} blank lines.  @xref{@code{@@sp}}.

@item @@ss@{@}
Generate the German sharp-S es-zet letter, @ss{}.  @xref{Inserting Accents}.

@item @@strong @{@var{text}@}
Emphasize @var{text} more strongly than @code{@@emph}, by using
@strong{boldface} where possible; enclosed in asterisks in Info.
@xref{emph & strong, , Emphasizing Text}.

@item @@sub @{@var{text}@}
Set @var{text} as a subscript.  @xref{Inserting Subscripts and Superscripts}.

@item @@subheading @var{title}
Print an unnumbered subsection-like heading, but omit from the table
of contents of a printed manual.  In Info, the title is underlined
with hyphens.  @xref{@code{@@unnumberedsubsec @@appendixsubsec @@subheading}}.

@item @@subsection @var{title}
Begin a subsection within a section.  The subsection title appears in
the table of contents.  In Info, the title is underlined with hyphens.
Same context-dependent numbering as @code{@@section}.
@xref{@code{@@subsection}}.

@item @@subsubheading @var{title}
Print an unnumbered subsubsection-like heading, but omit from the
table of contents of a printed manual.  In Info, the title is
underlined with periods.  @xref{@code{@@subsubsection}}.

@item @@subsubsection @var{title}
Begin a subsubsection within a subsection.  The subsubsection title
appears in the table of contents.  In Info, the title is underlined
with periods.  Same context-dependent numbering as @code{@@section}.
@xref{@code{@@subsubsection}}.

@item @@subtitle @var{title}
In a printed manual, set a subtitle in a normal sized font flush to
the right-hand side of the page.  Not relevant to Info, which does not
have title pages.  @xref{@code{@@title @@subtitle @@author}}.

@item @@summarycontents
Print a short table of contents.  Synonym for @code{@@shortcontents}.
@xref{Contents, , Generating a Table of Contents}.

@item @@sup @{@var{text}@}
Set @var{text} as a superscript.  @xref{Inserting Subscripts and Superscripts}.

@item @@syncodeindex @var{from-index} @var{to-index}
Merge the index named in the first argument into the index named in
the second argument, formatting the entries from the first index with
@code{@@code}.  @xref{Combining Indices}.

@item @@synindex @var{from-index} @var{to-index}
Merge the index named in the first argument into the index named in
the second argument.  Do not change the font of @var{from-index}
entries.  @xref{Combining Indices}.

@item @@t@{@var{text}@}
Set @var{text} in a @t{fixed-width}, typewriter-like font.  No effect
in Info.  @xref{Fonts}.

@item @@tab
Separate columns in a row of a multitable.  @xref{Multitable Rows}.

@item @@table @var{formatting-command}
Begin a two-column table (description list), using @code{@@item} for
each entry.  Write each first column entry on the same line as
@code{@@item}.  First column entries are printed in the font resulting
from @var{formatting-command}.  Pair with @code{@@end table}.
@xref{Two-column Tables, , Making a Two-column Table}.  Also see
@ref{@code{@@ftable @@vtable}}, and @ref{@code{@@itemx}}.

@item @@TeX@{@}
Generate the @TeX{} logo.  @xref{@code{@@TeX @@LaTeX}}.

@item @@tex
Enter @TeX{} completely.  Pair with @code{@@end tex}.  @xref{Raw
Formatter Commands}.

@item @@textdegree@{@}
Generate the degree symbol.  @xref{@code{@@textdegree}}.

@item @@thischapter
@itemx @@thischaptername
@itemx @@thischapternum
@itemx @@thisfile
@itemx @@thispage
@itemx @@thistitle
Only allowed in a heading or footing.  Stands for, respectively, the
number and name of the current chapter (in the format `Chapter 1:
Title'), the current chapter name only, the current chapter number
only, the filename, the current page number, and the title of the
document, respectively.  @xref{Custom Headings, , How to Make Your Own
Headings}.

@item @@TH@{@}
@itemx @@th@{@}
Generate the uppercase and lowercase Icelandic letter thorn, respectively:
@TH{}, @th{}.  @xref{Inserting Accents}.

@item @@tie@{@}
Generate a normal interword space at which a line break is not
allowed.  @xref{@code{@@tie}}.

@item @@tieaccent@{@var{cc}@}
Generate a tie-after accent over the next two characters @var{cc}, as in
`@tieaccent{oo}'.  @xref{Inserting Accents}.

@item @@tindex @var{entry}
Add @var{entry} to the index of data types.  @xref{Index Entries, ,
Defining the Entries of an Index}.

@item @@title @var{title}
In a printed manual, set a title flush to the left-hand side of the
page in a larger than normal font and underline it with a black rule.
Not relevant to Info, which does not have title pages.
@xref{@code{@@title @@subtitle @@author}}.

@item @@titlefont@{@var{text}@}
In a printed manual, print @var{text} in a larger than normal font.
@xref{@code{@@titlefont @@center @@sp}}.

@item @@titlepage
Begin the title page.  Write the command on a line of its own, paired
with @code{@@end titlepage}.  Nothing between @code{@@titlepage} and
@code{@@end titlepage} appears in Info.  @xref{@code{@@titlepage}}.

@item @@today@{@}
Insert the current date, in `1 Jan 1900' style.  @xref{Custom
Headings, , How to Make Your Own Headings}.

@item @@top @var{title}
Mark the topmost @code{@@node} in the file, which must be defined on
the line immediately preceding the @code{@@top} command.  The title is
formatted as a chapter-level heading.  The entire top node, including
the @code{@@node} and @code{@@top} lines, are normally enclosed with
@code{@@ifnottex ... @@end ifnottex}.  In @TeX{} and
@code{texinfo-format-buffer}, the @code{@@top} command is merely a
synonym for @code{@@unnumbered}.  @xref{@command{makeinfo} Pointer
Creation}.

@item @@U@{@var{hex}@}
Output a representation of Unicode character U+@var{hex}.
@xref{Inserting Unicode}.

@item @@u@{@var{c}@}
@itemx @@ubaraccent@{@var{c}@}
@itemx @@udotaccent@{@var{c}@}
Generate a breve, underbar, or underdot accent, respectively, over or
under the character @var{c}, as in @u{o}, @ubaraccent{o},
@udotaccent{o}.  @xref{Inserting Accents}.

@item @@unmacro @var{macroname}
Undefine the macro @code{@@@var{macroname}} if it has been defined.
@xref{Defining Macros}.

@item @@unnumbered @var{title}
Begin a chapter that appears without chapter numbers of any kind.  The
title appears in the table of contents.  In Info, the title is
underlined with asterisks.  @xref{@code{@@unnumbered @@appendix}}.

@item @@unnumberedsec @var{title}
Begin a section that appears without section numbers of any kind.  The
title appears in the table of contents of a printed manual.  In Info,
the title is underlined with equal signs.  @xref{@code{@@unnumberedsec
@@appendixsec @@heading}}.

@item @@unnumberedsubsec @var{title}
Begin an unnumbered subsection.  The title appears in the table of
contents.  In Info, the title is underlined with hyphens.
@xref{@code{@@unnumberedsubsec @@appendixsubsec @@subheading}}.

@item @@unnumberedsubsubsec @var{title}
Begin an unnumbered subsubsection.  The title appears in the table of
contents.  In Info, the title is underlined with periods.
@xref{@code{@@subsubsection}}.

@item @@uref@{@var{url}[, @var{displayed-text}][, @var{replacement}@}
@itemx @@url@{@var{url}[, @var{displayed-text}][, @var{replacement}@}
Define a cross-reference to an external uniform resource locator,
e.g., for the World Wide Web.  @xref{@code{@@url}}.

@item @@urefbreakstyle @var{style}
Specify how @code{@@uref}/@code{@@url} should break at special
characters: @code{after}, @code{before}, @code{none}.
@xref{@code{@@url}}.

@item @@v@{@var{c}@}
Generate check accent over the character @var{c}, as in @v{o}.
@xref{Inserting Accents}.

@item @@validatemenus @var{on-off}
Control whether menus can be automatically generated.  @xref{Writing a
Menu}.

@item @@value@{@var{txivar}@}
Insert the value, if any, of the Texinfo variable @var{txivar},
previously defined by @code{@@set}.  @xref{@code{@@set @@clear
@@value}}.

@item @@var@{@var{metasyntactic-variable}@}
Highlight a metasyntactic variable, which is something that stands for
another piece of text.  @xref{@code{@@var}}.

@item @@verb@{@var{delim} @var{literal} @var{delim}@}
Output @var{literal}, delimited by the single character @var{delim},
exactly as is (in the fixed-width font), including any whitespace or
Texinfo special characters.  @xref{@code{@@verb}}.

@item @@verbatim
Output the text of the environment exactly as is (in the fixed-width
font).  Pair with @code{@@end verbatim}.  @xref{@code{@@verbatim}}.

@item @@verbatiminclude @var{filename}
Output the contents of @var{filename} exactly as is (in the
fixed-width font).  @xref{@code{@@verbatiminclude}}.

@item @@vindex @var{entry}
Add @var{entry} to the index of variables.  @xref{Index Entries, ,
Defining the Entries of an Index}.

@item @@vskip @var{amount}
In a printed manual, insert whitespace so as to push text on the
remainder of the page towards the bottom of the page.  Used in
formatting the copyright page with the argument @samp{0pt plus
1filll}.  (Note spelling of @samp{filll}.)  @code{@@vskip} may be used
only in contexts ignored for Info.  @xref{Copyright}.

@item @@vtable @var{formatting-command}
Begin a two-column table, using @code{@@item} for each entry.
Automatically enter each of the items in the first column into the
index of variables.  Pair with @code{@@end vtable}.  The same as
@code{@@table}, except for indexing.  @xref{@code{@@ftable @@vtable}}.

@item @@w@{@var{text}@}
Disallow line breaks within @var{text}.  @xref{@code{@@w}}.

@item @@xml
Enter XML completely.  Pair with @code{@@end xml}.  @xref{Raw
Formatter Commands}.

@item @@xref@{@var{node}, [@var{entry}], [@var{node-title}], [@var{info-file}], [@var{manual}]@}
Make a reference that starts with `See' in a printed manual.  Follow
command with a punctuation mark.  Only the first argument is
mandatory.  @xref{@code{@@xref}}.

@item @@xrefautomaticsectiontitle @var{on-off}
By default, use the section title instead of the node name in cross
references.  @xref{Three Arguments}.

@end table

@node Command Contexts
@section @@-Command Contexts

@cindex Contexts, of @@-commands

Here we describe approximately which @@-commands can be used in which
contexts.  It not exhaustive or meant to be a complete reference.
Discrepancies between the information here and the @code{makeinfo} or
@TeX{} implementations are most likely to be resolved in favor of the
implementation.

By @dfn{general text} below, we mean anything except sectioning and
other such outer-level document commands, such as @code{@@section},
@code{@@node}, and @code{@@setfilename}.

@code{@@c}, @code{@@comment} and @code{@@if ... @@end if} conditional
commands may appear anywhere (except the conditionals must still be on
lines by themselves).  @code{@@caption} may only appear in
@code{@@float} but may contain general text.  @code{@@footnote}
content likewise.

@@-commands with braces marking text (such as @code{@@strong},
@code{@@sc}, @code{@@asis}) may contain raw formatter commands such as
@code{@@html} but no other block commands (other commands terminated
by @code{@@end}) and may not be split across paragraphs, but may
otherwise contain general text.

In addition to the block command restriction, on @code{@@center},
@code{@@exdent} and @code{@@item} in @code{@@table} lines, @@-commands
that makes only sense in a paragraph are not accepted, such as
@code{@@indent}.

In addition to the above, sectioning commands cannot contain
@code{@@anchor}, @code{@@footnote} or @code{@@verb}.

In addition to the above, remaining commands (@code{@@node},
@code{@@anchor}, @code{@@printindex}, @code{@@ref}, @code{@@math},
@code{@@cindex}, @code{@@url}, @code{@@image}, and so on) cannot
contain cross-reference commands (@code{@@ref}, @code{@@xref},
@code{@@pxref} and @code{@@inforef}).  In one last addition,
@code{@@shortcaption} may only appear inside @code{@@float}.

For precise and complete information, we suggest looking into the
test suite in the sources, which exhaustively tries combinations.

@node Obsolete @@-Commands
@section Obsolete @@-Commands

Here are Texinfo @@-commands which are obsolete or have been removed
completely.  This section is for historical purposes.

@ftable @code
@item @@setcontentsaftertitlepage
@cindex Contents, after title page
@cindex Table of contents, after title page
In the past, the contents commands were sometimes placed at the end of
the file, after any indices and just before the @code{@@bye}, but we
no longer recommend this.
This command could be used by a user printing a manual, to force the
contents to be printed after the title page
(after the @samp{@@end titlepage} line)
even if the @code{@@contents} command was at the end of the manual.  It
now does nothing.

@item @@setshortcontentsaftertitlepage
This placed the short table of contents after the @samp{@@end titlepage}
command even if the @code{@@shortcontents} command was at the end.  It
now does nothing.
@end ftable

@node Tips
@appendix Tips and Hints

Here are some tips for writing Texinfo documentation:

@cindex Tips
@cindex Usage tips
@cindex Hints
@itemize @bullet
@item
Write in the present tense, not in the past or the future.

@item
Write actively!  For example, write ``We recommend that @dots{}'' rather
than ``It is recommended that @dots{}''.

@item
Use 70 or 72 as your fill column.  Longer lines are hard to read.

@item
Include a copyright notice and copying permissions.
@end itemize

@subsubheading Index, Index, Index!

Write many index entries, in different ways.
Readers like indices; they are helpful and convenient.

Although it is easiest to write index entries as you write the body of
the text, some people prefer to write entries afterwards.  In either
case, write an entry before the paragraph to which it applies.  This
way, an index entry points to the first page of a paragraph that is
split across pages.

Here are more index-related hints we have found valuable:

@itemize @bullet
@item
Write each index entry differently, so each entry refers to a different
place in the document.

@item
Write index entries only where a topic is discussed significantly.  For
example, it is not useful to index ``debugging information'' in a
chapter on reporting bugs.  Someone who wants to know about debugging
information will certainly not find it in that chapter.

@item
Consistently capitalize the first word of every concept index entry,
or else consistently use lowercase.  Terse entries often call for
lowercase; longer entries for capitalization.  Whichever case
convention you use, please use one or the other consistently!  Mixing
the two styles looks bad.

@item
Always capitalize or use uppercase for those words in an index for
which this is proper, such as names of countries or acronyms.  Always
use the appropriate case for case-sensitive names, such as those in C or
Lisp.

@item
Write the indexing commands that refer to a whole section immediately
after the section command, and write the indexing commands that refer to
a paragraph before that paragraph.

In the example that follows, a blank line comes after the index
entry for ``Leaping'':

@example
@group
@@section The Dog and the Fox
@@cindex Jumping, in general
@@cindex Leaping

@@cindex Dog, lazy, jumped over
@@cindex Lazy dog jumped over
@@cindex Fox, jumps over dog
@@cindex Quick fox jumps over dog
The quick brown fox jumps over the lazy dog.
@end group
@end example

@noindent
(Note that the example shows entries for the same concept that are
written in different ways---@samp{Lazy dog}, and @samp{Dog, lazy}---so
readers can look up the concept in different ways.)
@end itemize

@subsubheading Blank Lines

@itemize @bullet
@item
Insert a blank line between a sectioning command and the first following
sentence or paragraph, or between the indexing commands associated with
the sectioning command and the first following sentence or paragraph, as
shown in the tip on indexing.  It makes the source easier to read.

@item
Always insert a blank line before a @code{@@table} command and after an
@code{@@end table} command; but never insert a blank line after an
@code{@@table} command.

@need 1000
For example,

@example
@group
Types of fox:

@@table @@samp
@@item Quick
Jump over lazy dogs.
@end group

@group
@@item Brown
Also jump over lazy dogs.
@@end table

@end group
@group
@@noindent
On the other hand, @dots{}
@end group
@end example

Insert blank lines before and after @code{@@itemize} @dots{} @code{@@end
itemize} and @code{@@enumerate} @dots{} @code{@@end enumerate} in the
same way.
@end itemize

@subsubheading Complete Phrases

Complete phrases are easier to read than @dots{}

@itemize @bullet
@item
Write entries in an itemized list as complete sentences; or at least, as
complete phrases.  Incomplete expressions @dots{} awkward @dots{} like
this.

@item
Write the prefatory sentence or phrase for a multi-item list or table as
a complete expression.  Do not write ``You can set:''; instead, write
``You can set these variables:''.  The former expression sounds cut off.
@end itemize

@subsubheading Editions, Dates and Versions

Include edition numbers, version numbers, and dates in the
@code{@@copying} text (for people reading the Texinfo file, and for the
legal copyright in the output files).  Then use @code{@@insertcopying}
in the @code{@@titlepage} section for people reading the printed
output (@pxref{Short Sample}).

It is easiest to handle such version information using @code{@@set}
and @code{@@value}.  @xref{@code{@@value} Example}, and @ref{GNU
Sample Texts}.

@subsubheading Definition Commands

Definition commands are @code{@@deffn}, @code{@@defun},
@code{@@defmac}, and the like, and enable you to write descriptions in
a uniform format.

@itemize @bullet
@item
Write just one definition command for each entity you define with a
definition command.  The automatic indexing feature creates an index
entry that leads the reader to the definition.

@item
Use @code{@@table} @dots{} @code{@@end table} in an appendix that
contains a summary of functions, not @code{@@deffn} or other definition
commands.
@end itemize

@subsubheading Capitalization

@itemize @bullet
@item
Capitalize ``Texinfo''; it is a name.  Do not write the @samp{x} or
@samp{i} in uppercase.

@item
Capitalize ``Info''; it is a name.

@item
Write @TeX{} using the @code{@@TeX@{@}} command.  Note the uppercase
@samp{T} and @samp{X}.  This command causes the formatters to
typeset the name according to the wishes of Donald Knuth, who wrote
@TeX{}.  (Likewise @code{@@LaTeX@{@}} for @LaTeX{}.)
@end itemize

@subsubheading Spaces

Do not use spaces to format a Texinfo file, except inside of
@code{@@example} @dots{} @code{@@end example} and other literal
environments and commands.

@need 700
For example, @TeX{} fills the following:

@example
@group
   @@kbd@{C-x v@}
   @@kbd@{M-x vc-next-action@}
      Perform the next logical operation
      on the version-controlled file
      corresponding to the current buffer.
@end group
@end example

@need 950
@noindent
so it looks like this:

@iftex
@quotation
   @kbd{C-x v}
   @kbd{M-x vc-next-action}
      Perform the next logical operation on the version-controlled file
      corresponding to the current buffer.
@end quotation
@end iftex
@ifnottex
@quotation
`C-x v' `M-x vc-next-action' Perform the next logical operation on the
version-controlled file corresponding to the current buffer.
@end quotation
@end ifnottex

@noindent
In this case, the text should be formatted with
@code{@@table}, @code{@@item}, and @code{@@itemx}, to create a table.

@subsubheading @@code, @@samp, @@var, and @samp{---}

@itemize @bullet
@item
Use @code{@@code} around Lisp symbols, including command names.
For example,

@example
The main function is @@code@{vc-next-action@}, @dots{}
@end example

@item
Avoid putting letters such as @samp{s} immediately after an
@samp{@@code}.  Such letters look bad.

@item
Use @code{@@var} around meta-variables.  Do not write angle brackets
around them.

@item
Use three hyphens in a row, @samp{---}, to indicate a long dash.  @TeX{}
typesets these as a long dash and the Info formatters reduce three
hyphens to two.
@end itemize

@subsubheading Periods Outside of Quotes

Place periods and other punctuation marks @emph{outside} of quotations,
unless the punctuation is part of the quotation.  This practice goes
against some publishing conventions in the United States, but enables the
reader to distinguish between the contents of the quotation and the
whole passage.

For example, you should write the following sentence with the period
outside the end quotation marks:

@example
Evidently, @samp{au} is an abbreviation for ``author''.
@end example

@noindent
since @samp{au} does @emph{not} serve as an  abbreviation for
@samp{author.} (with a period following the word).

@subsubheading Introducing New Terms

@itemize @bullet
@item
Introduce new terms so that a reader who does not know them can
understand them from context; or write a definition for the term.

For example, in the following, the terms ``check in'', ``register'' and
``delta'' are all appearing for the first time; the example sentence should be
rewritten so they are understandable.

@quotation
The major function assists you in checking in a file to your
version control system and registering successive sets of changes to
it as deltas.
@end quotation

@item
Use the @code{@@dfn} command around a word being introduced, to indicate
that the reader should not expect to know the meaning already, and
should expect to learn the meaning from this passage.
@end itemize

@subsubheading Program Invocation Nodes

You can invoke programs such as Emacs, GCC, and @code{gawk} from a
shell.  The documentation for each program should contain a section that
describes this.  Unfortunately, if the node names and titles for these
sections are all different, they are difficult for users to find.

So, there is a convention to name such sections with a phrase beginning
with the word `Invoking', as in `Invoking Emacs'; this way, users can
find the section easily.

@subsubheading ANSI C Syntax

When you use @code{@@example} to describe a C function's calling
conventions, use the ANSI C syntax, like this:

@example
void dld_init (char *@@var@{path@});
@end example

@noindent
And in the subsequent discussion, refer to the argument values by
writing the same argument names, again highlighted with
@code{@@var}.

@need 800
Avoid the obsolete style that looks like this:

@example
#include <dld.h>

dld_init (path)
  char *path;
@end example

Also, it is best to avoid writing @code{#include} above the
declaration just to indicate that the function is declared in a
header file.  The practice may give the misimpression that the
@code{#include} belongs near the declaration of the function.  Either
state explicitly which header file holds the declaration or, better
yet, name the header file used for a group of functions at the
beginning of the section that describes the functions.

@anchor{texi-elements-by-size}
@subsubheading Node Length

Keep nodes (sections) to a reasonable length, whatever reasonable
might be in the given context.  Don't hesitate to break up long nodes
into subnodes and have an extensive tree structure; that's what it's
there for.  Many times, readers will probably try to find a single
specific point in the manual, using search, indexing, or just plain
guessing, rather than reading the whole thing from beginning to end.

You can use the @command{texi-elements-by-size} utility to see a list
of all nodes (or sections) in the document, sorted by size (either
lines or words), to find candidates for splitting.  It's in the
@file{util/} subdirectory of the Texinfo sources.

@subsubheading Bad Examples

Here are several examples of bad writing to avoid:

In this example, say, `` @dots{} you must @code{@@dfn}@{check
in@} the new version.''  That flows better.

@quotation
When you are done editing the file, you must perform a
@code{@@dfn}@{check in@}.
@end quotation

In the following example, say, ``@dots{} makes a unified interface such as VC
mode possible.''

@quotation
SCCS, RCS and other version-control systems all perform similar
functions in broadly similar ways (it is this resemblance which makes
a unified control mode like this possible).
@end quotation

And in this example, you should specify what `it' refers to:

@quotation
If you are working with other people, it assists in coordinating
everyone's changes so they do not step on each other.
@end quotation

@subsubheading And Finally @dots{}

@itemize @bullet
@item
Pronounce @TeX{} as if the @samp{X} were a Greek `chi', as the last
sound in the name `Bach'.  But pronounce Texinfo as in `speck':
``teckinfo''.

@item
Write notes for yourself at the very end of a Texinfo file after the
@code{@@bye}.  None of the formatters process text after the
@code{@@bye}; it is as if the text were within @code{@@ignore} @dots{}
@code{@@end ignore}.
@end itemize

@node Sample Texinfo Files
@appendix Sample Texinfo Files
@cindex Sample Texinfo files

The first example from the first chapter (@pxref{Short Sample}) is
given here in its entirety, without commentary.  The second example
includes the full texts to be used in GNU manuals.

@menu
* Short Sample Texinfo File::
* GNU Sample Texts::
* Verbatim Copying License::
* All-permissive Copying License::
@end menu

@node Short Sample Texinfo File
@section Short Sample
@cindex Sample Texinfo file, no comments

Here is a complete, short sample Texinfo file.  You can see this file,
with comments, in the first chapter.  @xref{Short Sample}.

In a nutshell: The @command{makeinfo} program transforms a Texinfo
source file such as this into an Info file or HTML; and @TeX{} typesets
it for a printed manual.

@sp 1
@example
\input texinfo
@@settitle Sample Manual 1.0

@@copying
This is a short example of a complete Texinfo file.

Copyright @@copyright@{@} 2016 Free Software Foundation, Inc.
@@end copying

@@titlepage
@@title Sample Title
@@page
@@vskip 0pt plus 1filll
@@insertcopying
@@end titlepage

@@c Output the table of the contents at the beginning.
@@contents

@@ifnottex
@@node Top
@@top GNU Sample

This manual is for GNU Sample
(version @@value@{VERSION@}, @@value@{UPDATED@}).
@@end ifnottex

@@menu
* First Chapter::    The first chapter is the
                      only chapter in this sample.
* Index::            Complete index.
@@end menu

@@node First Chapter
@@chapter First Chapter

@@cindex chapter, first

This is the first chapter.
@@cindex index entry, another

Here is a numbered list.

@@enumerate
@@item
This is the first item.

@@item
This is the second item.
@@end enumerate

@@node Index
@@unnumbered Index

@@printindex cp

@@bye
@end example

@node GNU Sample Texts
@section GNU Sample Texts

@cindex GNU sample texts
@cindex Sample texts, GNU
@cindex Full texts, GNU

Following is a sample Texinfo document with the full texts that should
be used (adapted as necessary) in GNU manuals.

As well as the legal texts, it also serves as a practical example of how
many elements in a GNU system can affect the manual.  If you're not
familiar with all these different elements, don't worry.  They're not
required and a perfectly good manual can be written without them.
They're included here nonetheless because many manuals do (or could)
benefit from them.

@xref{Short Sample}, for a minimal example of a Texinfo file.
@xref{Beginning and Ending a File}, for a full explanation of that
minimal example.

Here are some notes on the example:

@itemize @bullet
@item
@cindex $Id
@cindex CVS $Id
@cindex RCS $Id
@cindex Documentation identification
@cindex Identification of documentation
The @samp{$Id:} comment is for the CVS
(@url{http://www.nongnu.org/cvs/}), RCS (@pxref{Top,,, rcs, Revision
Control System}) and other version control systems, which expand it
into a string such as:

@example
$Id$
@end example

(This is potentially useful in all sources that use version control,
not just manuals.)  You may wish to include the @samp{$Id:} comment in
the @code{@@copying} text, if you want a completely unambiguous
reference to the documentation source version.

If you want to literally write @t{@w{$}Id$}, use @code{@@w}:
@code{@@w@{$@}Id$}.  Unfortunately, this technique does not work in
plain text output, where it's not clear what should be done.

@item
@pindex automake@r{, and version info}
@vindex UPDATED @r{Automake variable}
@vindex VERSION @r{Automake variable}
@pindex time-stamp.el
The @file{version.texi} in the @code{@@include} command is maintained
automatically by Automake (@pxref{Top,,, automake, GNU Automake}).  It
sets the @samp{VERSION} and @samp{UPDATED} values used elsewhere.  If
your distribution doesn't use Automake, but you do use Emacs, you may
find the time-stamp.el package helpful (@pxref{Time Stamps,,, emacs,
The GNU Emacs Manual}).

@item
The @code{@@syncodeindex} command reflects the recommendation to use
only one index where possible, to make it easier for readers to look up
index entries.

@item
The @code{@@dircategory} is for constructing the Info directory.
@xref{Installing Dir Entries}, which includes a variety of recommended
category names.

@item
The `Invoking' node is a GNU standard to help users find the basic
information about command-line usage of a given program.  @xref{Manual
Structure Details,,, standards, GNU Coding Standards}.

@item
@cindex GNU Free Documentation License, including entire
@cindex Free Documentation License, including entire
It is best to include the entire GNU Free Documentation License in a GNU
manual, unless the manual is only a few pages long.  Of course this
sample is even shorter than that, but it includes the FDL anyway in
order to show one conventional way to do so.  The @file{fdl.texi} file
is available on the GNU machines and in the Texinfo and other GNU
source distributions.

The FDL provides for omitting itself under certain conditions, but in
that case the sample texts given here have to be modified.  @xref{GNU
Free Documentation License}.

@item
If the FSF is not the copyright holder, then use the appropriate name.

@item
If your manual is published on paper by the FSF or is longer than 400
pages, you should include the standard FSF cover texts (@pxref{License
Notices for Documentation,,, maintain, GNU Maintainer Information}).

@item
For documents that express your personal views, feelings or
experiences, it is more appropriate to use a license permitting only
verbatim copying, rather than the FDL@.  @xref{Verbatim Copying
License}.

@end itemize

Here is the sample document:

@verbatim
\input texinfo   @c -*-texinfo-*-
@comment $Id@w{$}
@comment %**start of header
@include version.texi
@settitle GNU Sample @value{VERSION}
@syncodeindex pg cp
@comment %**end of header
@copying
This manual is for GNU Sample (version @value{VERSION}, @value{UPDATED}),
which is an example in the Texinfo documentation.

Copyright @copyright{} 2016 Free Software Foundation, Inc.

@quotation
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3 or
any later version published by the Free Software Foundation; with no
Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
Texts.  A copy of the license is included in the section entitled
``GNU Free Documentation License''.
@end quotation
@end copying

@dircategory Texinfo documentation system
@direntry
* sample: (sample)Invoking sample.
@end direntry

@titlepage
@title GNU Sample
@subtitle for version @value{VERSION}, @value{UPDATED}
@author A.U. Thor (@email{bug-sample@@gnu.org})
@page
@vskip 0pt plus 1filll
@insertcopying
@end titlepage

@contents

@ifnottex
@node Top
@top GNU Sample

This manual is for GNU Sample (version @value{VERSION}, @value{UPDATED}).
@end ifnottex

@menu
* Invoking sample::
* GNU Free Documentation License::
* Index::
@end menu

@node Invoking sample
@chapter Invoking sample

@pindex sample
@cindex invoking @command{sample}

This is a sample manual.  There is no sample program to
invoke, but if there were, you could see its basic usage
and command line options here.

@node GNU Free Documentation License
@appendix GNU Free Documentation License

@include fdl.texi

@node Index
@unnumbered Index

@printindex cp

@bye
@end verbatim

@node Verbatim Copying License
@section Verbatim Copying License

@cindex Verbatim copying license
@cindex License for verbatim copying

For software manuals and other documentation, it is critical to use a
license permitting free redistribution and updating, so that when a free
program is changed, the documentation can be updated as well.

On the other hand, for documents that express your personal views,
feelings or experiences, it is more appropriate to use a license
permitting only verbatim copying.

Here is sample text for such a license permitting verbatim copying only.
This is just the license text itself.  For a complete sample document,
see the previous sections.

@verbatim
@copying
This document is a sample for allowing verbatim copying only.

Copyright @copyright{} 2016 Free Software Foundation, Inc.

@quotation
Permission is granted to make and distribute verbatim copies
of this entire document without royalty provided the
copyright notice and this permission notice are preserved.
@end quotation
@end copying
@end verbatim

@node All-permissive Copying License
@section All-permissive Copying License

@cindex All-permissive copying license
@cindex License for all-permissive copying

For software manuals and other documentation, it is important to use a
license permitting free redistribution and updating, so that when a free
program is changed, the documentation can be updated as well.

On the other hand, for small supporting files, short manuals (under 300
lines long) and rough documentation (README files, INSTALL files, etc.),
the full FDL would be overkill.  They can use a simple all-permissive
license.

Here is sample text for such an all-permissive license.  This is just
the license text itself.  For a complete sample document, see the
previous sections.

@example
Copyright @@copyright@{@} 2016 Free Software Foundation, Inc.

Copying and distribution of this file, with or without modification,
are permitted in any medium without royalty provided the copyright
notice and this notice are preserved.
@end example

@node Texinfo Mode
@appendix Using Texinfo Mode
@cindex Texinfo mode
@cindex Mode, using Texinfo
@cindex GNU Emacs
@cindex Emacs

You may edit a Texinfo file with any text editor you choose.  A Texinfo
file is no different from any other ASCII file.  However, GNU Emacs
comes with a special mode, called Texinfo mode, that provides Emacs
commands and tools to help ease your work.

@menu
* Texinfo Mode Overview::       How Texinfo mode can help you.
* Emacs Editing::               Texinfo mode adds to GNU Emacs' general
                                  purpose editing features.
* Inserting::                   How to insert frequently used @@-commands.
* Showing the Structure::       How to show the structure of a file.
* Updating Nodes and Menus::    How to update or create new nodes and menus.
* Info Formatting::             How to format for Info.
* Printing::                    How to format and print part or all of a file.
* Texinfo Mode Summary::        Summary of all the Texinfo mode commands.
@end menu

@node Texinfo Mode Overview
@section Texinfo Mode Overview

Texinfo mode provides special features for working with Texinfo files.
You can:

@itemize @bullet
@item
Insert frequently used @@-commands.

@item
Automatically create @code{@@node} lines.

@item
Show the structure of a Texinfo source file.

@item
Automatically create or update the `Next',
`Previous', and `Up' pointers of a node.

@item
Automatically create or update menus.

@item
Automatically create a master menu.

@item
Format a part or all of a file for Info.

@item
Typeset and print part or all of a file.
@end itemize

Perhaps the two most helpful features are those for inserting frequently
used @@-commands and for creating node pointers and menus.

@node Emacs Editing
@section The Usual GNU Emacs Editing Commands

In most cases, the usual Text mode commands work the same in Texinfo
mode as they do in Text mode.  Texinfo mode adds new editing commands
and tools to GNU Emacs' general purpose editing features.  The major
difference concerns filling.  In Texinfo mode, the paragraph
separation variable and syntax table are redefined so that Texinfo
commands that should be on lines of their own are not inadvertently
included in paragraphs.  Thus, the @kbd{M-q} (@code{fill-paragraph})
command will refill a paragraph but not mix an indexing command on a
line adjacent to it into the paragraph.

In addition, Texinfo mode sets the @code{page-delimiter} variable to
the value of @code{texinfo-chapter-level-regexp}; by default, this is
a regular expression matching the commands for chapters and their
equivalents, such as appendices.  With this value for the page
delimiter, you can jump from chapter title to chapter title with the
@kbd{C-x ]} (@code{forward-page}) and @kbd{C-x [}
(@code{backward-page}) commands and narrow to a chapter with the
@kbd{C-x n p} (@code{narrow-to-page}) command.  (@xref{Pages, , ,emacs,
The GNU Emacs Manual}, for details about the page commands.)

You may name a Texinfo file however you wish, but the convention is to
end a Texinfo file name with one of the extensions
@file{.texinfo}, @file{.texi}, @file{.txi}, or @file{.tex}.  A longer
extension is preferred, since it is explicit, but a shorter extension
may be necessary for operating systems that limit the length of file
names.  GNU Emacs automatically enters Texinfo mode when you visit a
file with a @file{.texinfo}, @file{.texi} or @file{.txi}
extension.  Also, Emacs switches to Texinfo mode
when you visit a
file that has @samp{-*-texinfo-*-} in its first line.  If ever you are
in another mode and wish to switch to Texinfo mode, type @code{M-x
texinfo-mode}.

Like all other Emacs features, you can customize or enhance Texinfo
mode as you wish.  In particular, the keybindings are very easy to
change.  The keybindings described here are the default or standard
ones.

@node Inserting
@section Inserting Frequently Used Commands
@cindex Inserting frequently used commands
@cindex Frequently used commands, inserting
@cindex Commands, inserting them

Texinfo mode provides commands to insert various frequently used
@@-commands into the buffer.  You can use these commands to save
keystrokes.

The insert commands are invoked by typing @kbd{C-c} twice and then the
first letter of the @@-command:

@table @kbd
@item  C-c C-c c
@itemx M-x texinfo-insert-@@code
@findex texinfo-insert-@@code
Insert @code{@@code@{@}} and put the
cursor between the braces.

@item  C-c C-c d
@itemx M-x texinfo-insert-@@dfn
@findex texinfo-insert-@@dfn
Insert @code{@@dfn@{@}} and put the
cursor between the braces.

@item  C-c C-c e
@itemx M-x texinfo-insert-@@end
@findex texinfo-insert-@@end
Insert @code{@@end} and attempt to insert the correct following word,
such as @samp{example} or @samp{table}.  (This command does not handle
nested lists correctly, but inserts the word appropriate to the
immediately preceding list.)

@item  C-c C-c i
@itemx M-x texinfo-insert-@@item
@findex texinfo-insert-@@item
Insert @code{@@item} and put the
cursor at the beginning of the next line.

@item  C-c C-c k
@itemx M-x texinfo-insert-@@kbd
@findex texinfo-insert-@@kbd
Insert @code{@@kbd@{@}} and put the
cursor between the braces.

@item  C-c C-c n
@itemx M-x texinfo-insert-@@node
@findex texinfo-insert-@@node
Insert @code{@@node} and a comment line
listing the sequence for the `Next',
`Previous', and `Up' nodes.
Leave point after the @code{@@node}.

@item  C-c C-c o
@itemx M-x texinfo-insert-@@noindent
@findex texinfo-insert-@@noindent
Insert @code{@@noindent} and put the
cursor at the beginning of the next line.

@item  C-c C-c s
@itemx M-x texinfo-insert-@@samp
@findex texinfo-insert-@@samp
Insert @code{@@samp@{@}} and put the
cursor between the braces.

@item  C-c C-c t
@itemx M-x texinfo-insert-@@table
@findex texinfo-insert-@@table
Insert @code{@@table} followed by a @key{SPC}
and leave the cursor after the @key{SPC}.

@item  C-c C-c v
@itemx M-x texinfo-insert-@@var
@findex texinfo-insert-@@var
Insert @code{@@var@{@}} and put the
cursor between the braces.

@item  C-c C-c x
@itemx M-x texinfo-insert-@@example
@findex texinfo-insert-@@example
Insert @code{@@example} and put the
cursor at the beginning of the next line.

@c M-@{  was the binding for texinfo-insert-braces;
@c in Emacs 19, backward-paragraph will take this binding.
@item C-c C-c @{
@itemx M-x texinfo-insert-braces
@findex texinfo-insert-braces
Insert @code{@{@}} and put the cursor between the braces.

@item C-c @}
@itemx C-c  ]
@itemx M-x up-list
@findex up-list
Move from between a pair of braces forward past the closing brace.
Typing @kbd{C-c ]} is easier than typing @kbd{C-c @}}, which
is, however, more mnemonic; hence the two keybindings.  (Also, you can
move out from between braces by typing @kbd{C-f}.)
@end table

To put a command such as @w{@code{@@code@{@dots{}@}}} around an
@emph{existing} word, position the cursor in front of the word and type
@kbd{C-u 1 C-c C-c c}.  This makes it easy to edit existing plain text.
The value of the prefix argument tells Emacs how many words following
point to include between braces---@samp{1} for one word, @samp{2} for
two words, and so on.  Use a negative argument to enclose the previous
word or words.  If you do not specify a prefix argument, Emacs inserts
the @@-command string and positions the cursor between the braces.  This
feature works only for those @@-commands that operate on a word or words
within one line, such as @code{@@kbd} and @code{@@var}.

This set of insert commands was created after analyzing the frequency
with which different @@-commands are used in the @cite{GNU Emacs
Manual} and the @cite{GDB Manual}.  If you wish to add your own insert
commands, you can bind a keyboard macro to a key, use abbreviations,
or extend the code in @file{texinfo.el}.

@findex texinfo-start-menu-description
@cindex Menu description, start
@cindex Description for menu, start
@kbd{C-c C-c C-d} (@code{texinfo-start-menu-description}) is an insert
command that works differently from the other insert commands.  It
inserts a node's section or chapter title in the space for the
description in a menu entry line.  (A menu entry has three parts, the
entry name, the node name, and the description.  Only the node name is
required, but a description helps explain what the node is about.
@xref{Menu Parts, , The Parts of a Menu}.)

To use @code{texinfo-start-menu-description}, position point in a menu
entry line and type @kbd{C-c C-c C-d}.  The command looks for and copies
the title that goes with the node name, and inserts the title as a
description; it positions point at beginning of the inserted text so you
can edit it.  The function does not insert the title if the menu entry
line already contains a description.

This command is only an aid to writing descriptions; it does not do the
whole job.  You must edit the inserted text since a title tends to use
the same words as a node name but a useful description uses different
words.

@node Showing the Structure
@section Showing the Sectioning Structure of a File
@cindex Showing the sectioning structure of a file
@cindex Sectioning structure of a file, showing
@cindex Structure of a file, showing
@cindex Outline of file structure, showing
@cindex Contents-like outline of file structure
@cindex File sectioning structure, showing
@cindex Texinfo file sectioning structure, showing

You can show the sectioning structure of a Texinfo file by using the
@kbd{C-c C-s} command (@code{texinfo-show-structure}).  This command
lists the lines that begin with the @@-commands for @code{@@chapter},
@code{@@section}, and the like.  It constructs what amounts to a table
of contents.  These lines are displayed in another buffer called the
@samp{*Occur*} buffer.  In that buffer, you can position the cursor
over one of the lines and use the @kbd{C-c C-c} command
(@code{occur-mode-goto-occurrence}), to jump to the corresponding spot
in the Texinfo file.

@table @kbd
@item  C-c C-s
@itemx M-x texinfo-show-structure
@findex texinfo-show-structure
Show the @code{@@chapter}, @code{@@section}, and such lines of a
Texinfo file.

@item  C-c C-c
@itemx M-x occur-mode-goto-occurrence
@findex occur-mode-goto-occurrence
Go to the line in the Texinfo file corresponding to the line under the
cursor in the @file{*Occur*} buffer.
@end table

If you call @code{texinfo-show-structure} with a prefix argument by
typing @w{@kbd{C-u C-c C-s}}, it will list not only those lines with the
@@-commands for @code{@@chapter}, @code{@@section}, and the like, but
also the @code{@@node} lines.  You can use @code{texinfo-show-structure}
with a prefix argument to check whether the `Next', `Previous', and `Up'
pointers of an @code{@@node} line are correct.

Often, when you are working on a manual, you will be interested only
in the structure of the current chapter.  In this case, you can mark
off the region of the buffer that you are interested in by using the
@kbd{C-x n n} (@code{narrow-to-region}) command and
@code{texinfo-show-structure} will work on only that region.  To see
the whole buffer again, use @w{@kbd{C-x n w}} (@code{widen}).
(@xref{Narrowing, , , emacs, The GNU Emacs Manual}, for more
information about the narrowing commands.)

@vindex page-delimiter
@cindex Page delimiter in Texinfo mode
In addition to providing the @code{texinfo-show-structure} command,
Texinfo mode sets the value of the page delimiter variable to match
the chapter-level @@-commands.  This enables you to use the @kbd{C-x
]} (@code{forward-page}) and @kbd{C-x [} (@code{backward-page})
commands to move forward and backward by chapter, and to use the
@kbd{C-x n p} (@code{narrow-to-page}) command to narrow to a chapter.
@xref{Pages, , , emacs, The GNU Emacs Manual}, for more information
about the page commands.

@node Updating Nodes and Menus
@section Updating Nodes and Menus

@cindex Updating nodes and menus
@cindex Create nodes, menus automatically
@cindex Insert nodes, menus automatically
@cindex Automatically insert nodes, menus

Texinfo mode provides commands for automatically creating or updating
menus and node pointers.  The commands are called ``update'' commands
because their most frequent use is for updating a Texinfo file after you
have worked on it; but you can use them to insert the `Next',
`Previous', and `Up' pointers into an @code{@@node} line that has none
and to create menus in a file that has none.

If you do not use any updating commands, you need to write menus by
hand, which is a tedious task.

@menu
* Updating Commands::           Five major updating commands.
* Updating Requirements::       How to structure a Texinfo file for
                                  using the updating command.
* Other Updating Commands::     How to indent descriptions, insert
                                  missing nodes lines, and update
                                  nodes in sequence.
@end menu

@node Updating Commands
@subsection The Updating Commands

You can use the updating commands to:

@itemize @bullet
@item
insert or update the `Next', `Previous', and `Up' pointers of a node,

@item
insert or update the menu for a section, and

@item
create a master menu for a Texinfo source file.
@end itemize

You can also use the commands to update all the nodes and menus in a
region or in a whole Texinfo file.

The updating commands work only with conventional Texinfo files, which
are structured hierarchically like books.  In such files, a structuring
command line must follow closely after each @code{@@node} line, except
for the `Top' @code{@@node} line.  (A @dfn{structuring command line} is
a line beginning with @code{@@chapter}, @code{@@section}, or other
similar command.)

You can write the structuring command line on the line that follows
immediately after an @code{@@node} line or else on the line that
follows after a single @code{@@comment} line or a single
@code{@@ifinfo} line.  You cannot interpose more than one line between
the @code{@@node} line and the structuring command line; and you may
interpose only a @code{@@comment} line or an @code{@@ifinfo} line.

Commands which work on a whole buffer require that the `Top' node be
followed by a node with a @code{@@chapter} or equivalent-level command.
The menu updating commands will not create a main or master menu for a
Texinfo file that has only @code{@@chapter}-level nodes!  The menu
updating commands only create menus @emph{within} nodes for lower level
nodes.  To create a menu of chapters, you must provide a `Top'
node.

The menu updating commands remove menu entries that refer to other Info
files since they do not refer to nodes within the current buffer.  This
is a deficiency.  Rather than use menu entries, you can use cross
references to refer to other Info files.  None of the updating commands
affect cross-references.

Texinfo mode has five updating commands that are used most often: two
are for updating the node pointers or menu of a single node (or a
region); two are for updating every node pointer and menu in a file;
and one, the @code{texinfo-master-menu} command, is for creating a
master menu for a complete file, and optionally, for updating every
node and menu in the whole Texinfo file.

The @code{texinfo-master-menu} command is the primary command:

@table @kbd
@item C-c C-u m
@itemx M-x texinfo-master-menu
@findex texinfo-master-menu
Create or update a master menu that includes all the other menus
(incorporating the descriptions from pre-existing menus, if
any).

With an argument (prefix argument, @kbd{C-u,} if interactive), first create or
update all the nodes and all the regular menus in the buffer before
constructing the master menu.  (@xref{The Top Node, , The Top Node and
Master Menu}, for more about a master menu.)

For @code{texinfo-master-menu} to work, the Texinfo file must have a
`Top' node and at least one subsequent node.

After extensively editing a Texinfo file, you can type the following:

@example
C-u M-x texinfo-master-menu
@exdent or
C-u C-c C-u m
@end example

@noindent
This updates all the nodes and menus completely and all at once.
@end table

The other major updating commands do smaller jobs and are designed for
the person who updates nodes and menus as he or she writes a Texinfo
file.

@need 1000
The commands are:

@table @kbd
@item C-c C-u C-n
@itemx M-x texinfo-update-node
@findex texinfo-update-node
Insert the `Next', `Previous', and `Up' pointers for the node that point is
within (i.e., for the @code{@@node} line preceding point).  If the
@code{@@node} line has pre-existing `Next', `Previous', or `Up'
pointers in it, the old pointers are removed and new ones inserted.
With an argument (prefix argument, @kbd{C-u}, if interactive), this command
updates all @code{@@node} lines in the region (which is the text
between point and mark).

@item C-c C-u C-m
@itemx M-x texinfo-make-menu
@findex texinfo-make-menu
Create or update the menu in the node that point is within.
With an argument (@kbd{C-u} as prefix argument, if
interactive), the command makes or updates menus for the
nodes which are either within or a part of the
region.

Whenever @code{texinfo-make-menu} updates an existing menu, the
descriptions from that menu are incorporated into the new menu.  This
is done by copying descriptions from the existing menu to the entries
in the new menu that have the same node names.  If the node names are
different, the descriptions are not copied to the new menu.

@item C-c C-u C-e
@itemx M-x texinfo-every-node-update
@findex texinfo-every-node-update
Insert or update the `Next', `Previous', and `Up' pointers for every
node in the buffer.

@item C-c C-u C-a
@itemx M-x texinfo-all-menus-update
@findex texinfo-all-menus-update
Create or update all the menus in the buffer.  With an argument
(@kbd{C-u} as prefix argument, if interactive), first insert
or update all the node
pointers before working on the menus.

If a master menu exists, the @code{texinfo-all-menus-update} command
updates it; but the command does not create a new master menu if none
already exists.  (Use the @code{texinfo-master-menu} command for
that.)

When working on a document that does not merit a master menu, you can
type the following:

@example
C-u C-c C-u C-a
@exdent or
C-u M-x texinfo-all-menus-update
@end example

@noindent
This updates all the nodes and menus.
@end table

The @code{texinfo-column-for-description} variable specifies the
column to which menu descriptions are indented.  By default, the value
is 32 although it can be useful to reduce it to as low as 24.  You
can set the variable via customization (@pxref{Customization,,,
emacs, The GNU Emacs Manual}) or with the @kbd{M-x set-variable}
command (@pxref{Examining, , Examining and Setting Variables, emacs,
The GNU Emacs Manual}).

Also, the @code{texinfo-indent-menu-description} command may be used to
indent existing menu descriptions to a specified column.  Finally, if
you wish, you can use the @code{texinfo-insert-node-lines} command to
insert missing @code{@@node} lines into a file.  (@xref{Other Updating
Commands}, for more information.)

@node Updating Requirements
@subsection Updating Requirements
@cindex Updating requirements
@cindex Requirements for updating commands

To use the updating commands, you must organize the Texinfo file
hierarchically with chapters, sections, subsections, and the like.
When you construct the hierarchy of the manual, do not `jump down'
more than one level at a time: you can follow the `Top' node with a
chapter, but not with a section; you can follow a chapter with a
section, but not with a subsection.  However, you may `jump up' any
number of levels at one time---for example, from a subsection to a
chapter.

Each @code{@@node} line, with the exception of the line for the `Top'
node, must be followed by a line with a structuring command such as
@code{@@chapter}, @code{@@section}, or
@code{@@unnumberedsubsec}.

Each @code{@@node} line/structuring-command line combination
must look either like this:

@example
@group
@@node     Comments,  Minimum, Conventions, Overview
@@comment  node-name, next,    previous,    up
@@section Comments
@end group
@end example

or like this (without the @code{@@comment} line):

@example
@group
@@node Comments, Minimum, Conventions, Overview
@@section Comments
@end group
@end example

or like this (without the explicit node pointers):

@example
@group
@@node Comments
@@section Comments
@end group
@end example

@noindent
In this example, `Comments' is the name of both the node and the
section.  The next node is called `Minimum' and the previous node is
called `Conventions'.  The `Comments' section is within the `Overview'
node, which is specified by the `Up' pointer.  (Instead of an
@code{@@comment} line, you may also write an @code{@@ifinfo} line.)

If a file has a `Top' node, it must be called @samp{top} or @samp{Top}
and be the first node in the file.

The menu updating commands create a menu of sections within a chapter,
a menu of subsections within a section, and so on.  This means that
you must have a `Top' node if you want a menu of chapters.

Incidentally, the @code{makeinfo} command will create an Info file for a
hierarchically organized Texinfo file that lacks `Next', `Previous' and
`Up' pointers.  Thus, if you can be sure that your Texinfo file will be
formatted with @code{makeinfo}, you have no need for the update node
commands.  (@xref{Creating an Info File}, for more information about
@code{makeinfo}.)

@node Other Updating Commands
@subsection Other Updating Commands

In addition to the five major updating commands, Texinfo mode
possesses several less frequently used updating commands:

@table @kbd
@item M-x texinfo-insert-node-lines
@findex texinfo-insert-node-lines
Insert @code{@@node} lines before the @code{@@chapter},
@code{@@section}, and other sectioning commands wherever they are
missing throughout a region in a Texinfo file.

With an argument (@kbd{C-u} as prefix argument, if interactive), the
command @code{texinfo-insert-node-lines} not only inserts
@code{@@node} lines but also inserts the chapter or section titles as
the names of the corresponding nodes.  In addition, it inserts the
titles as node names in pre-existing @code{@@node} lines that lack
names.  Since node names should be more concise than section or
chapter titles, you must manually edit node names so inserted.

For example, the following marks a whole buffer as a region and inserts
@code{@@node} lines and titles throughout:

@example
C-x h C-u M-x texinfo-insert-node-lines
@end example

This command inserts titles as node names in @code{@@node} lines; the
@code{texinfo-start-menu-description} command (@pxref{Inserting,
Inserting Frequently Used Commands}) inserts titles as descriptions in
menu entries, a different action.  However, in both cases, you need to
edit the inserted text.

@item M-x texinfo-multiple-files-update
@findex texinfo-multiple-files-update @r{(in brief)}
Update nodes and menus in a document built from several separate files.
With @kbd{C-u} as a prefix argument, create and insert a master menu in
the outer file.  With a numeric prefix argument, such as @kbd{C-u 2}, first
update all the menus and all the `Next', `Previous', and `Up' pointers
of all the included files before creating and inserting a master menu in
the outer file.  The @code{texinfo-multiple-files-update} command is
described in the appendix on @code{@@include} files.
@xref{@code{texinfo-multiple-files-update}}.

@item M-x texinfo-indent-menu-description
@findex texinfo-indent-menu-description
Indent every description in the menu following point to the specified
column.  You can use this command to give yourself more space for
descriptions.  With an argument (@kbd{C-u} as prefix argument, if
interactive), the @code{texinfo-indent-menu-description} command indents
every description in every menu in the region.  However, this command
does not indent the second and subsequent lines of a multi-line
description.

@item M-x texinfo-sequential-node-update
@findex texinfo-sequential-node-update
Insert the names of the nodes immediately following and preceding the
current node as the `Next' or `Previous' pointers regardless of those
nodes' hierarchical level.  This means that the `Next' node of a
subsection may well be the next chapter.  Sequentially ordered nodes are
useful for novels and other documents that you read through
sequentially.  (However, in Info, the @kbd{g *} command lets
you look through the file sequentially, so sequentially ordered nodes
are not strictly necessary.)  With an argument (prefix argument, if
interactive), the @code{texinfo-sequential-node-update} command
sequentially updates all the nodes in the region.
@end table

@node Info Formatting
@section Formatting for Info
@cindex Formatting for Info
@cindex Running an Info formatter
@cindex Info formatting

Texinfo mode provides several commands for formatting part or all of a
Texinfo file for Info.  Often, when you are writing a document, you
want to format only part of a file---that is, a region.

You can use either the @code{texinfo-format-region} or the
@code{makeinfo-region} command to format a region:

@table @kbd
@findex texinfo-format-region
@item  C-c C-e C-r
@itemx M-x texinfo-format-region
@itemx C-c C-m C-r
@itemx M-x makeinfo-region
Format the current region for Info.
@end table

You can use either the @code{texinfo-format-buffer} or the
@code{makeinfo-buffer} command to format a whole buffer:

@table @kbd
@findex texinfo-format-buffer
@item  C-c C-e C-b
@itemx M-x texinfo-format-buffer
@itemx C-c C-m C-b
@itemx M-x makeinfo-buffer
Format the current buffer for Info.
@end table

@need 1000
For example, after writing a Texinfo file, you can type the following:

@example
C-u C-c C-u m
@exdent or
C-u M-x texinfo-master-menu
@end example

@noindent
This updates all the nodes and menus.  Then type the following to create
an Info file:

@example
C-c C-m C-b
@exdent or
M-x makeinfo-buffer
@end example

@xref{Creating an Info File} for details about Info formatting.

@node Printing
@comment node-name,  next,  previous,  up
@section Printing
@cindex Formatting for printing
@cindex Printing a region or buffer
@cindex Region formatting and printing
@cindex Buffer formatting and printing
@cindex Part of file formatting and printing

Typesetting and printing a Texinfo file is a multi-step process in
which you first create a file for printing (called a DVI file), and
then print the file.  Optionally, you may also create indices.  To do
this, you must run the @code{texindex} command after first running the
@code{tex} typesetting command; and then you must run the @code{tex}
command again.  Or else run the @code{texi2dvi} command which
automatically creates indices as needed (@pxref{Format with
@command{texi2dvi}}).

Often, when you are writing a document, you want to typeset and print
only part of a file to see what it will look like.  You can use the
@code{texinfo-tex-region} and related commands for this purpose.  Use
the @code{texinfo-tex-buffer} command to format all of a
buffer.

@table @kbd
@item  C-c C-t C-b
@itemx M-x texinfo-tex-buffer
@findex texinfo-tex-buffer
Run @code{texi2dvi} on the buffer.  In addition to running @TeX{} on the
buffer, this command automatically creates or updates indices as
needed.

@item  C-c C-t C-r
@itemx M-x texinfo-tex-region
@findex texinfo-tex-region
Run @TeX{} on the region.

@item C-c C-t C-i
@itemx M-x texinfo-texindex
Run @code{texindex} to sort the indices of a Texinfo file formatted with
@code{texinfo-tex-region}.  The @code{texinfo-tex-region} command does
not run @code{texindex} automatically; it only runs the @code{tex}
typesetting command.  You must run the @code{texinfo-tex-region} command
a second time after sorting the raw index files with the @code{texindex}
command.  (Usually, you do not format an index when you format a region,
only when you format a buffer.  Now that the @code{texi2dvi} command
exists, there is little or no need for this command.)

@item C-c C-t C-p
@itemx M-x texinfo-tex-print
@findex texinfo-tex-print
Print the file (or the part of the file) previously formatted with
@code{texinfo-tex-buffer} or @code{texinfo-tex-region}.
@end table

For @code{texinfo-tex-region} or @code{texinfo-tex-buffer} to work, the
file @emph{must} start with a @samp{\input texinfo} line and must
include a @code{@@settitle} line.  The file must end with @code{@@bye}
on a line by itself.  (When you use @code{texinfo-tex-region}, you must
surround the @code{@@settitle} line with start-of-header and
end-of-header lines.)

@xref{Hardcopy}, for a description of the other @TeX{} related
commands, such as @code{tex-show-print-queue}.

@node Texinfo Mode Summary
@section Texinfo Mode Summary

In Texinfo mode, each set of commands has default keybindings that
begin with the same keys.  All the commands that are custom-created
for Texinfo mode begin with @kbd{C-c}.  The keys are somewhat
mnemonic.

@subheading Insert Commands

The insert commands are invoked by typing @kbd{C-c} twice and then the
first letter of the @@-command to be inserted.  (It might make more
sense mnemonically to use @kbd{C-c C-i}, for `custom insert', but
@kbd{C-c C-c} is quick to type.)

@example
C-c C-c c       @r{Insert} @samp{@@code}.
C-c C-c d       @r{Insert} @samp{@@dfn}.
C-c C-c e       @r{Insert} @samp{@@end}.
C-c C-c i       @r{Insert} @samp{@@item}.
C-c C-c n       @r{Insert} @samp{@@node}.
C-c C-c s       @r{Insert} @samp{@@samp}.
C-c C-c v       @r{Insert} @samp{@@var}.
C-c @{       @r{Insert braces.}
C-c ]
C-c @}       @r{Move out of enclosing braces.}

@group
C-c C-c C-d     @r{Insert a node's section title}
               @r{in the space for the description}
               @r{in a menu entry line.}
@end group
@end example

@subheading Show Structure

The @code{texinfo-show-structure} command is often used within a
narrowed region.

@example
C-c C-s         @r{List all the headings.}
@end example

@subheading The Master Update Command

The @code{texinfo-master-menu} command creates a master menu; and can
be used to update every node and menu in a file as well.

@c Probably should use @tables in this section.
@example
@group
C-c C-u m
M-x texinfo-master-menu
               @r{Create or update a master menu.}
@end group

@group
C-u C-c C-u m   @r{With @kbd{C-u} as a prefix argument, first}
               @r{create or update all nodes and regular}
               @r{menus, and then create a master menu.}
@end group
@end example

@subheading Update Pointers

The update pointer commands are invoked by typing @kbd{C-c C-u} and
then either @kbd{C-n} for @code{texinfo-update-node} or @kbd{C-e} for
@code{texinfo-every-node-update}.

@example
C-c C-u C-n     @r{Update a node.}
C-c C-u C-e     @r{Update every node in the buffer.}
@end example

@subheading Update Menus

Invoke the  update menu commands by typing @kbd{C-c C-u}
and then either @kbd{C-m} for @code{texinfo-make-menu} or
@kbd{C-a} for @code{texinfo-all-menus-update}.  To update
both nodes and menus at the same time, precede @kbd{C-c C-u
C-a} with @kbd{C-u}.

@example
C-c C-u C-m     @r{Make or update a menu.}

@group
C-c C-u C-a     @r{Make or update all}
               @r{menus in a buffer.}
@end group

@group
C-u C-c C-u C-a @r{With @kbd{C-u} as a prefix argument,}
               @r{first create or update all nodes and}
               @r{then create or update all menus.}
@end group
@end example

@subheading Format for Info

The Info formatting commands that are written in Emacs Lisp are
invoked by typing @kbd{C-c C-e} and then either @kbd{C-r} for a region
or @kbd{C-b} for the whole buffer.

The Info formatting commands that are written in C and based on the
@code{makeinfo} program are invoked by typing @kbd{C-c C-m} and then
either @kbd{C-r} for a region or @kbd{C-b} for the whole buffer.

@need 800
@noindent
Use the @code{texinfo-format@dots{}} commands:

@example
@group
C-c C-e C-r     @r{Format the region.}
C-c C-e C-b     @r{Format the buffer.}
@end group
@end example

@need 750
@noindent
Use @code{makeinfo}:

@example
C-c C-m C-r     @r{Format the region.}
C-c C-m C-b     @r{Format the buffer.}
C-c C-m C-l     @r{Recenter the @code{makeinfo} output buffer.}
C-c C-m C-k     @r{Kill the @code{makeinfo} formatting job.}
@end example

@subheading Typeset and Print

The @TeX{} typesetting and printing commands are invoked by typing
@kbd{C-c C-t} and then another control command: @kbd{C-r} for
@code{texinfo-tex-region}, @kbd{C-b} for @code{texinfo-tex-buffer},
and so on.

@example
C-c C-t C-r     @r{Run @TeX{} on the region.}
C-c C-t C-b     @r{Run} @code{texi2dvi} @r{on the buffer.}
C-c C-t C-i     @r{Run} @code{texindex}.
C-c C-t C-p     @r{Print the DVI file.}
C-c C-t C-q     @r{Show the print queue.}
C-c C-t C-d     @r{Delete a job from the print queue.}
C-c C-t C-k     @r{Kill the current @TeX{} formatting job.}
C-c C-t C-x     @r{Quit a currently stopped @TeX{} formatting job.}
C-c C-t C-l     @r{Recenter the output buffer.}
@end example

@subheading Other Updating Commands

The remaining updating commands do not have standard keybindings because
they are rarely used.

@example
@group
M-x texinfo-insert-node-lines
               @r{Insert missing @code{@@node} lines in region.}
               @r{With @kbd{C-u} as a prefix argument,}
               @r{use section titles as node names.}
@end group

@group
M-x texinfo-multiple-files-update
               @r{Update a multi-file document.}
               @r{With @kbd{C-u 2} as a prefix argument,}
               @r{create or update all nodes and menus}
               @r{in all included files first.}
@end group

@group
M-x texinfo-indent-menu-description
               @r{Indent descriptions.}
@end group

@group
M-x texinfo-sequential-node-update
               @r{Insert node pointers in strict sequence.}
@end group
@end example

@node Headings
@appendix Page Headings
@cindex Headings
@cindex Footings
@cindex Page numbering
@cindex Page headings
@cindex Formatting headings and footings

Most printed manuals contain headings along the top of every page
except the title and copyright pages.  Some manuals also contain
footings. @c HTML output also supports something like these, but in a
@c completely different way: @pxref{Customizing HTML Page Layout}.
Headings and footings have no meaning in Info or the other output
formats.

@menu
* Headings Introduced::         Conventions for using page headings.
* Heading Format::              Standard page heading formats.
* Heading Choice::              How to specify the type of page heading.
* Custom Headings::             How to create your own headings and footings.
@end menu

@node Headings Introduced
@section Headings Introduced

Texinfo provides standard page heading formats for manuals that are
printed on one side of each sheet of paper and for manuals that are
printed on both sides of the paper.  Typically, you will use these
formats, but you can specify your own format if you wish.

In addition, you can specify whether chapters should begin on a new
page, or merely continue the same page as the previous chapter; and if
chapters begin on new pages, you can specify whether they must be
odd-numbered pages.

By convention, a book is printed on both sides of each sheet of paper.
When you open a book, the right-hand page is odd-numbered, and
chapters begin on right-hand pages---a preceding left-hand page is
left blank if necessary.  Reports, however, are often printed on just
one side of paper, and chapters begin on a fresh page immediately
following the end of the preceding chapter.  In short or informal
reports, chapters often do not begin on a new page at all, but are
separated from the preceding text by a small amount of whitespace.

The @code{@@setchapternewpage} command controls whether chapters begin
on new pages, and whether one of the standard heading formats is used.
In addition, Texinfo has several heading and footing commands that you
can use to generate your own heading and footing formats.

In Texinfo, headings and footings are single lines at the tops and
bottoms of pages; you cannot create multiline headings or footings.
Each header or footer line is divided into three parts: a left part, a
middle part, and a right part.  Any part, or a whole line, may be left
blank.  Text for the left part of a header or footer line is set
flushleft; text for the middle part is centered; and, text for the
right part is set flushright.

@node Heading Format
@section Standard Heading Formats

Texinfo provides two standard heading formats, one for manuals printed
on one side of each sheet of paper, and the other for manuals printed
on both sides of the paper.

By default, nothing is specified for the footing of a Texinfo file,
so the footing remains blank.

The standard format for single-sided printing consists of a header
line in which the left-hand part contains the name of the chapter, the
central part is blank, and the right-hand part contains the page
number.

@need 950
A single-sided page looks like this:

@example
@group
  _______________________
 |                       |
 | chapter   page number |
 |                       |
 | Start of text ...     |
 | ...                   |
 |                       |
@end group
@end example

The standard format for two-sided printing depends on whether the page
number is even or odd.  By convention, even-numbered pages are on the
left- and odd-numbered pages are on the right.  (@TeX{} will adjust the
widths of the left- and right-hand margins.  Usually, widths are
correct, but during double-sided printing, it is wise to check that
pages will bind properly---sometimes a printer will produce output in
which the even-numbered pages have a larger right-hand margin than the
odd-numbered pages.)

In the standard double-sided format, the left part of the left-hand
(even-numbered) page contains the page number, the central part is
blank, and the right part contains the title (specified by the
@code{@@settitle} command).  The left part of the right-hand
(odd-numbered) page contains the name of the chapter, the central part
is blank, and the right part contains the page number.

@need 750
Two pages, side by side as in an open book, look like this:

@example
@group
  _______________________     _______________________
 |                       |   |                       |
 | page number     title |   | chapter   page number |
 |                       |   |                       |
 | Start of text ...     |   | More  text ...        |
 | ...                   |   | ...                   |
 |                       |   |                       |
@end group
@end example

@noindent
The chapter name is preceded by the word ``Chapter'', the chapter number
and a colon.  This makes it easier to keep track of where you are in the
manual.

@node Heading Choice
@section Specifying the Type of Heading

@TeX{} does not begin to generate page headings for a standard Texinfo
file until it reaches the @code{@@end titlepage} command.  Thus, the
title and copyright pages are not numbered.  The @code{@@end
titlepage} command causes @TeX{} to begin to generate page headings
according to a standard format specified by the
@code{@@setchapternewpage} command that precedes the
@code{@@titlepage} section.

@need 1000
There are four possibilities:

@table @asis
@item No @code{@@setchapternewpage} command
Cause @TeX{} to specify the single-sided heading format, with chapters
on new pages. This is the same as @code{@@setchapternewpage on}.

@item @code{@@setchapternewpage on}
Specify the single-sided heading format, with chapters on new pages.

@item @code{@@setchapternewpage off}
Cause @TeX{} to start a new chapter on the same page as the last page
of the preceding chapter, after skipping some vertical whitespace.
Also cause @TeX{} to typeset for single-sided printing.  (You can
override the headers format with the @code{@@headings double} command;
@pxref{@code{@@headings}}.)

@item @code{@@setchapternewpage odd}
Specify the double-sided heading format, with chapters on new pages.
@end table

@noindent
Texinfo lacks a @code{@@setchapternewpage even} command.

@node Custom Headings
@section How to Make Your Own Headings

You can use the standard headings provided with Texinfo or specify
your own.  By default, Texinfo has no footers, so if you specify them,
the available page size for the main text will be slightly reduced.

Texinfo provides six commands for specifying headings and
footings:
@itemize @bullet
@item
@code{@@everyheading} and @code{@@everyfooting} generate page headers and
footers that are the same for both even- and odd-numbered pages.
@item
@code{@@evenheading} and @code{@@evenfooting} command generate headers
and footers for even-numbered (left-hand) pages.
@item
@code{@@oddheading} and @code{@@oddfooting} generate headers and footers
for odd-numbered (right-hand) pages.
@end itemize

Write custom heading specifications in the Texinfo file immediately
after the @code{@@end titlepage} command.  You must cancel the
predefined heading commands with the @code{@@headings off} command
before defining your own specifications.

@need 1000
Here is how to tell @TeX{} to place the chapter name at the left, the
page number in the center, and the date at the right of every header
for both even- and odd-numbered pages:

@example
@group
@@headings off
@@everyheading @@thischapter @@| @@thispage @@| @@today@{@}
@end group
@end example

@noindent
You need to divide the left part from the central part and the central
part from the right part by inserting @samp{@@|} between parts.
Otherwise, the specification command will not be able to tell where
the text for one part ends and the next part begins.

Each part can contain text or @@-commands.  The text is printed as if
the part were within an ordinary paragraph in the body of the page.
The @@-commands replace themselves with the page number, date, chapter
name, or whatever.

@need 950
Here are the six heading and footing commands:

@table @code
@item @@everyheading @var{left} @@| @var{center} @@| @var{right}
@itemx @@everyfooting @var{left} @@| @var{center} @@| @var{right}
@findex everyheading
@findex everyfooting
The `every' commands specify the format for both even- and odd-numbered
pages.  These commands are for documents that are printed on one side
of each sheet of paper, or for documents in which you want symmetrical
headers or footers.

@item @@evenheading @var{left} @@| @var{center} @@| @var{right}
@itemx @@oddheading  @var{left} @@| @var{center} @@| @var{right}
@itemx @@evenfooting @var{left} @@| @var{center} @@| @var{right}
@itemx @@oddfooting  @var{left} @@| @var{center} @@| @var{right}
@findex evenheading
@findex evenfooting
@findex oddheading
@findex oddfooting
The `even' and `odd' commands specify the format for even-numbered
pages and odd-numbered pages.  These commands are for books and
manuals that are printed on both sides of each sheet of paper.
@end table

Use the @samp{@@this@dots{}} series of @@-commands to
provide the names of chapters
and sections and the page number.  You can use the
@samp{@@this@dots{}} commands in the left, center, or right portions
of headers and footers, or anywhere else in a Texinfo file so long as
they are between @code{@@iftex} and @code{@@end iftex} commands.

@need 1000
Here are the @samp{@@this@dots{}} commands:

@table @code
@item @@thispage
@findex thispage
Expands to the current page number.

@item @@thissectionname
@findex thissectionname
Expands to the name of the current section.

@item @@thissectionnum
@findex thissectionnum
Expands to the number of the current section.

@item @@thissection
@findex thissection
Expands to the number and name of the current section, in the format
`Section 1: Title'.

@item @@thischaptername
@findex thischaptername
Expands to the name of the current chapter.

@item @@thischapternum
@findex thischapternum
Expands to the number of the current chapter, or letter of the current
appendix.

@item @@thischapter
@findex thischapter
Expands to the number and name of the current
chapter, in the format `Chapter 1: Title'.

@item @@thistitle
@findex thistitle
Expands to the name of the document, as specified by the
@code{@@settitle} command.

@item @@thisfile
@findex thisfile
For @code{@@include} files only: expands to the name of the current
@code{@@include} file.  If the current Texinfo source file is not an
@code{@@include} file, this command has no effect.  This command does
@emph{not} provide the name of the current Texinfo source file unless
it is an @code{@@include} file.  (@xref{Include Files}, for more
information about @code{@@include} files.)
@end table

@noindent
You can also use the @code{@@today@{@}} command, which expands to the
current date, in `1 Jan 1900' format.
@findex today

Other @@-commands and text are printed in a header or footer just as
if they were in the body of a page.  It is useful to incorporate text,
particularly when you are writing drafts:

@example
@group
@@headings off
@@everyheading @@emph@{Draft!@} @@| @@thispage @@| @@thischapter
@@everyfooting @@| @@| Version: 0.27: @@today@{@}
@end group
@end example

Beware of overlong titles: they may overlap another part of the
header or footer and blot it out.

If you have very short chapters and/or sections, several of them can
appear on a single page.  You can specify which chapters and sections
you want @code{@@thischapter}, @code{@@thissection} and other such
macros to refer to on such pages as follows:

@table @code
@item @@everyheadingmarks @var{ref}
@itemx @@everyfootingmarks @var{ref}
@findex everyheadingmarks
@findex everyfootingmarks
The @var{ref} argument can be either @code{top} (the @code{@@this...}
commands will refer to the chapter/section at the top of a page) or
@code{bottom} (the commands will reflect the situation at the bottom
of a page).  These @samp{@@every...} commands specify what to do on
both even- and odd-numbered pages.

@item @@evenheadingmarks @var{ref}
@itemx @@oddheadingmarks @var{ref}
@itemx @@evenfootingmarks @var{ref}
@itemx @@oddfootingmarks @var{ref}
@findex evenheadingmarks
@findex oddheadingmarks
@findex evenfootingmarks
@findex oddfootingmarks
These @samp{@@even...} and @samp{@@odd...} commands specify what to do
on only even- or odd-numbered pages, respectively.  The @var{ref}
argument is the same as with the @samp{@@every...} commands.
@end table

Write these commands immediately after the @code{@@...contents}
commands, or after the @code{@@end titlepage} command if you don't
have a table of contents or if it is printed at the end of your
manual.

By default the @code{@@this...} commands reflect the situation at the
bottom of a page both in headings and in footings.

@node Catching Mistakes
@appendix Catching Mistakes
@cindex Structure, catching mistakes in
@cindex Nodes, catching mistakes
@cindex Catching mistakes
@cindex Correcting mistakes
@cindex Mistakes, catching
@cindex Problems, catching
@cindex Debugging the Texinfo structure

Besides mistakes in the content of your documentation, there are two
kinds of mistake you can make with Texinfo: you can make mistakes with
@@-commands, and you can make mistakes with the structure of the nodes
and chapters.

Emacs has two tools for catching the @@-command mistakes and two for
catching structuring mistakes.

For finding problems with @@-commands, you can run @TeX{} or a region
formatting command on the region that has a problem; indeed, you can
run these commands on each region as you write it.

For finding problems with the structure of nodes and chapters, you can use
@kbd{C-c C-s} (@code{texinfo-show-structure}) and the related @code{occur}
command and you can use the @kbd{M-x Info-validate} command.

@menu
* @command{makeinfo} Preferred::          @code{makeinfo} finds errors.
* Debugging with Info::         How to catch errors with Info formatting.
* Debugging with @TeX{}::          How to catch errors with @TeX{} formatting.
* Using @code{texinfo-show-structure}:: How to use @code{texinfo-show-structure}.
* Using @code{occur}::                 How to list all lines containing a pattern.
* Running @code{Info-validate}::       How to find badly referenced nodes.
@end menu

@node @command{makeinfo} Preferred
@section @command{makeinfo} Preferred

@c anchor{makeinfo Preferred}@c prev name

The @code{makeinfo} program does an excellent job of catching errors
and reporting them---far better than @code{texinfo-format-region} or
@code{texinfo-format-buffer}.  In addition, the various functions for
automatically creating and updating node pointers and menus remove
many opportunities for human error.

If you can, use the updating commands to create and insert pointers
and menus.  These prevent many errors.  Then use @code{makeinfo} (or
its Texinfo mode manifestations, @code{makeinfo-region} and
@code{makeinfo-buffer}) to format your file and check for other
errors.  This is the best way to work with Texinfo.  But if you
cannot use @code{makeinfo}, or your problem is very puzzling, then you
may want to use the tools described in this appendix.

@node Debugging with Info
@section Catching Errors with Info Formatting
@cindex Catching errors with Info formatting
@cindex Debugging with Info formatting

After you have written part of a Texinfo file, you can use the
@code{texinfo-format-region} or the @code{makeinfo-region} command to
see whether the region formats properly.

Most likely, however, you are reading this section because for some
reason you cannot use the @code{makeinfo-region} command; therefore, the
rest of this section presumes that you are using
@code{texinfo-format-region}.

If you have made a mistake with an @@-command,
@code{texinfo-format-region} will stop processing at or after the
error and display an error message.  To see where in the buffer the
error occurred, switch to the @samp{*Info Region*} buffer; the cursor
will be in a position that is after the location of the error.  Also,
the text will not be formatted after the place where the error
occurred (or more precisely, where it was detected).

For example, if you accidentally end a menu with the command @code{@@end
menus} with an `s' on the end, instead of with @code{@@end menu}, you
will see an error message that says:

@example
@@end menus is not handled by texinfo
@end example

@noindent
The cursor will stop at the point in the buffer where the error
occurs, or not long after it.  The buffer will look like this:

@example
@group
---------- Buffer: *Info Region* ----------
* Menu:

* Using texinfo-show-structure::  How to use
                                 `texinfo-show-structure'
                                 to catch mistakes.
* Running Info-validate::         How to check for
                                 unreferenced nodes.
@@end menus
@point{}
---------- Buffer: *Info Region* ----------
@end group
@end example

The @code{texinfo-format-region} command sometimes provides slightly
odd error messages.  For example, the following cross-reference fails
to format:

@example
(@@xref@{Catching Mistakes, for more info.)
@end example

@noindent
In this case, @code{texinfo-format-region} detects the missing closing
brace but displays a message that says @samp{Unbalanced parentheses}
rather than @samp{Unbalanced braces}.  This is because the formatting
command looks for mismatches between braces as if they were
parentheses.

Sometimes @code{texinfo-format-region} fails to detect mistakes.  For
example, in the following, the closing brace is swapped with the
closing parenthesis:

@example
(@@xref@{Catching Mistakes), for more info.@}
@end example

@noindent
Formatting produces:
@example
(*Note for more info.: Catching Mistakes)
@end example

The only way for you to detect this error is to realize that the
reference should have looked like this:

@example
(*Note Catching Mistakes::, for more info.)
@end example

Incidentally, if you are reading this node in Info and type @kbd{f
@key{RET}} (@code{Info-follow-reference}), you will generate an error
message that says:

@example
No such node: "Catching Mistakes) The only way @dots{}
@end example

@noindent
This is because Info perceives the example of the error as the first
cross-reference in this node and if you type a @key{RET} immediately
after typing the Info @kbd{f} command, Info will attempt to go to the
referenced node.  If you type @kbd{f catch @key{TAB} @key{RET}}, Info
will complete the node name of the correctly written example and take
you to the `Catching Mistakes' node.  (If you try this, you can return
from the `Catching Mistakes' node by typing @kbd{l}
(@code{Info-last}).)

@node Debugging with @TeX{}
@section Debugging with @TeX{}
@cindex Catching errors with @TeX{} formatting
@cindex Debugging with @TeX{} formatting

You can also catch mistakes when you format a file with @TeX{}.

Usually, you will want to do this after you have run
@code{texinfo-format-buffer} (or, better, @code{makeinfo-buffer}) on
the same file, because @code{texinfo-format-buffer} sometimes displays
error messages that make more sense than @TeX{}.  (@xref{Debugging
with Info}, for more information.)

For example, @TeX{} was run on a Texinfo file, part of which is shown
here:

@example
---------- Buffer: texinfo.texi ----------
name of the Texinfo file as an extension.  The
@@samp@{??@} are `wildcards' that cause the shell to
substitute all the raw index files.  (@@xref@{sorting
indices, for more information about sorting
indices.)@@refill
---------- Buffer: texinfo.texi ----------
@end example

@noindent
(The cross-reference lacks a closing brace.)
@TeX{} produced the following output, after which it stopped:

@example
---------- Buffer: *tex-shell* ----------
Runaway argument?
@{sorting indices, for more information about sorting
indices.) @@refill @@ETC.
! Paragraph ended before @@xref was complete.
<to be read again>
                  @@par
l.27

?
---------- Buffer: *tex-shell* ----------
@end example

In this case, @TeX{} produced an accurate and
understandable error message:

@example
Paragraph ended before @@xref was complete.
@end example

@noindent
@samp{@@par} is an internal @TeX{} command of no relevance to Texinfo.
@samp{l.27} means that @TeX{} detected the problem on line 27 of the
Texinfo file.  The @samp{?} is the prompt @TeX{} uses in this
circumstance.

Unfortunately, @TeX{} is not always so helpful, and sometimes you must
truly be a Sherlock Holmes to discover what went wrong.

In any case, if you run into a problem like this, you can do one of three
things.

@enumerate
@item
You can tell @TeX{} to continue running and ignore just this error by
typing @key{RET} at the @samp{?} prompt.

@item
You can tell @TeX{} to continue running and to ignore all errors as best
it can by typing @kbd{r @key{RET}} at the @samp{?} prompt.

This is often the best thing to do.  However, beware: the one error
may produce a cascade of additional error messages as its consequences
are felt through the rest of the file.  To stop @TeX{} when it is
producing such an avalanche of error messages, type @kbd{C-c} (or
@kbd{C-c C-c}, if you are running a shell inside Emacs).

@item
You can tell @TeX{} to stop this run by typing @kbd{x @key{RET}}
at the @samp{?} prompt.
@end enumerate

If you are running @TeX{} inside Emacs, you need to switch to the shell
buffer and line at which @TeX{} offers the @samp{?} prompt.

Sometimes @TeX{} will format a file without producing error messages even
though there is a problem.  This usually occurs if a command is not ended
but @TeX{} is able to continue processing anyhow.  For example, if you fail
to end an itemized list with the @code{@@end itemize} command, @TeX{} will
write a DVI file that you can print out.  The only error message that
@TeX{} will give you is the somewhat mysterious comment:

@example
(@@end occurred inside a group at level 1)
@end example

@noindent
However, if you print the DVI file, you will find that the text
of the file that follows the itemized list is entirely indented as if
it were part of the last item in the itemized list.  The error message
is the way @TeX{} says that it expected to find an @code{@@end}
command somewhere in the file; but that it could not determine where
it was needed.

Another source of notoriously hard-to-find errors is a missing
@code{@@end group} command.  If you ever are stumped by
incomprehensible errors, look for a missing @code{@@end group} command
first.

If the Texinfo file lacks header lines,
@TeX{} may stop in the
beginning of its run and display output that looks like the following.
The @samp{*} indicates that @TeX{} is waiting for input.

@example
This is TeX, Version 3.14159 (Web2c 7.0)
(test.texinfo [1])
*
@end example

@noindent
In this case, simply type @kbd{\end @key{RET}} after the asterisk.  Then
write the header lines in the Texinfo file and run the @TeX{} command
again. (Note the use of the backslash, @samp{\}.  @TeX{} uses @samp{\}
instead of @samp{@@}; and in this circumstance, you are working
directly with @TeX{}, not with Texinfo.)

@node Using @code{texinfo-show-structure}
@section Using @code{texinfo-show-structure}

@cindex Showing the structure of a file
@findex texinfo-show-structure

It is not always easy to keep track of the nodes, chapters, sections, and
subsections of a Texinfo file.  This is especially true if you are revising
or adding to a Texinfo file that someone else has written.

In GNU Emacs, in Texinfo mode, the @code{texinfo-show-structure}
command lists all the lines that begin with the @@-commands that
specify the structure: @code{@@chapter}, @code{@@section},
@code{@@appendix}, and so on.  With an argument (@w{@kbd{C-u}}
as prefix argument, if interactive),
the command also shows the @code{@@node} lines.  The
@code{texinfo-show-structure} command is bound to @kbd{C-c C-s} in
Texinfo mode, by default.

The lines are displayed in a buffer called the @samp{*Occur*} buffer,
indented by hierarchical level.  For example, here is a part of what was
produced by running @code{texinfo-show-structure} on this manual:

@example
@group
Lines matching "^@@\\(chapter \\|sect\\|subs\\|subh\\|
unnum\\|major\\|chapheading \\|heading \\|appendix\\)"
in buffer texinfo.texi.
@dots{}
4177:@@chapter Nodes
4198:    @@heading Two Paths
4231:    @@section Node and Menu Illustration
4337:    @@section The @@code@{@@@@node@} Command
4393:        @@subheading Choosing Node and Pointer Names
4417:        @@subsection How to Write a @@code@{@@@@node@} Line
4469:        @@subsection @@code@{@@@@node@} Line Tips
@dots{}
@end group
@end example

This says that lines 4337, 4393, and 4417 of @file{texinfo.texi} begin
with the @code{@@section}, @code{@@subheading}, and @code{@@subsection}
commands respectively.  If you move your cursor into the @samp{*Occur*}
window, you can position the cursor over one of the lines and use the
@kbd{C-c C-c} command (@code{occur-mode-goto-occurrence}), to jump to
the corresponding spot in the Texinfo file.  @xref{Other Repeating
Search, , Using Occur, emacs, The GNU Emacs Manual}, for more
information about @code{occur-mode-goto-occurrence}.

The first line in the @samp{*Occur*} window describes the @dfn{regular
expression} specified by @var{texinfo-heading-pattern}.  This regular
expression is the pattern that @code{texinfo-show-structure} looks for.
@xref{Regexps, , Using Regular Expressions, emacs, The GNU Emacs Manual},
for more information.

When you invoke the @code{texinfo-show-structure} command, Emacs will
display the structure of the whole buffer.  If you want to see the
structure of just a part of the buffer, of one chapter, for example,
use the @kbd{C-x n n} (@code{narrow-to-region}) command to mark the
region.  (@xref{Narrowing, , , emacs, The GNU Emacs Manual}.)  This is
how the example used above was generated.  (To see the whole buffer
again, use @kbd{C-x n w} (@code{widen}).)

If you call @code{texinfo-show-structure} with a prefix argument by
typing @w{@kbd{C-u C-c C-s}}, it will list lines beginning with
@code{@@node} as well as the lines beginning with the @@-sign commands
for @code{@@chapter}, @code{@@section}, and the like.

You can remind yourself of the structure of a Texinfo file by looking at
the list in the @samp{*Occur*} window; and if you have mis-named a node
or left out a section, you can correct the mistake.

@node Using @code{occur}
@section Using @code{occur}

@cindex Occurrences, listing with @code{@@occur}
@findex occur

Sometimes the @code{texinfo-show-structure} command produces too much
information.  Perhaps you want to remind yourself of the overall structure
of a Texinfo file, and are overwhelmed by the detailed list produced by
@code{texinfo-show-structure}.  In this case, you can use the @code{occur}
command directly.  To do this, type:

@example
@kbd{M-x occur}
@end example

@noindent
and then, when prompted, type a @dfn{regexp}, a regular expression for
the pattern you want to match.  (@xref{Regexps, , Regular Expressions,
emacs, The GNU Emacs Manual}.)  The @code{occur} command works from
the current location of the cursor in the buffer to the end of the
buffer.  If you want to run @code{occur} on the whole buffer, place
the cursor at the beginning of the buffer.

For example, to see all the lines that contain the word
@samp{@@chapter} in them, just type @samp{@@chapter}.  This will
produce a list of the chapters.  It will also list all the sentences
with @samp{@@chapter} in the middle of the line.

If you want to see only those lines that start with the word
@samp{@@chapter}, type @samp{^@@chapter} when prompted by
@code{occur}.  If you want to see all the lines that end with a word
or phrase, end the last word with a @samp{$}; for example,
@samp{catching mistakes$}.  This can be helpful when you want to see
all the nodes that are part of the same chapter or section and
therefore have the same `Up' pointer.

@xref{Other Repeating Search, , Using Occur, emacs , The GNU Emacs Manual},
for more information.

@node Running @code{Info-validate}
@section Finding Badly Referenced Nodes

@anchor{Running Info-Validate}@c old name
@findex Info-validate
@cindex Nodes, checking for badly referenced
@cindex Checking for badly referenced nodes
@cindex Looking for badly referenced nodes
@cindex Finding badly referenced nodes
@cindex Badly referenced nodes

You can use the @code{Info-validate} command to check whether any of
the `Next', `Previous', `Up' or other node pointers fail to point to a
node.  This command checks that every node pointer points to an
existing node.  The @code{Info-validate} command works only on Info
files, not on Texinfo files.

The @code{makeinfo} program validates pointers automatically, so you
do not need to use the @code{Info-validate} command if you are using
@code{makeinfo}.  You only may need to use @code{Info-validate} if you
are unable to run @code{makeinfo} and instead must create an Info file
using @code{texinfo-format-region} or @code{texinfo-format-buffer}, or
if you write an Info file from scratch.

@menu
* Using @code{Info-validate}::         How to run @code{Info-validate}.
* Unsplit::                     How to create an unsplit file.
* Tagifying::                   How to tagify a file.
* Splitting::                   How to split a file manually.
@end menu

@node Using @code{Info-validate}
@subsection Using @code{Info-validate}

@cindex Using @code{Info-validate}
@cindex Info validating a large file
@cindex Validating a large file

To use @code{Info-validate}, visit the Info file you wish to check and
type:

@example
M-x Info-validate
@end example

@noindent
Note that the @code{Info-validate} command requires an uppercase
`I'@.  You may also need to create a tag table before running
@code{Info-validate}.  @xref{Tagifying}.

If your file is valid, you will receive a message that says ``File appears
valid''.  However, if you have a pointer that does not point to a node,
error messages will be displayed in a buffer called @samp{*problems in
info file*}.

For example, @code{Info-validate} was run on a test file that contained
only the first node of this manual.  One of the messages said:

@example
In node "Overview", invalid Next: Texinfo Mode
@end example

@noindent
This meant that the node called @samp{Overview} had a `Next' pointer that
did not point to anything (which was true in this case, since the test file
had only one node in it).

Now suppose we add a node named @samp{Texinfo Mode} to our test case
but we do not specify a `Previous' for this node.  Then we will get
the following error message:

@example
In node "Texinfo Mode", should have Previous: Overview
@end example

@noindent
This is because every `Next' pointer should be matched by a
`Previous' (in the node where the `Next' points) which points back.

@code{Info-validate} also checks that all menu entries and cross-references
point to actual nodes.

@code{Info-validate} requires a tag table and does not work with files
that have been split.  (The @code{texinfo-format-buffer} command
automatically splits large files.)  In order to use @code{Info-validate}
on a large file, you must run @code{texinfo-format-buffer} with an
argument so that it does not split the Info file; and you must create a
tag table for the unsplit file.

@node Unsplit
@subsection Creating an Unsplit File
@cindex Creating an unsplit file
@cindex Unsplit file creation

You can run @code{Info-validate} only on a single Info file that has a
tag table.  The command will not work on the indirect subfiles that
are generated when a master file is split.  If you have a large file
(longer than 300,000 bytes or so), you need to run the
@code{texinfo-format-buffer} or @code{makeinfo-buffer} command in such
a way that it does not create indirect subfiles.  You will also need
to create a tag table for the Info file.  After you have done this,
you can run @code{Info-validate} and look for badly referenced
nodes.

The first step is to create an unsplit Info file.  To prevent
@code{texinfo-format-buffer} from splitting a Texinfo file into
smaller Info files, give a prefix to the @kbd{M-x
texinfo-format-buffer} command:

@example
C-u M-x texinfo-format-buffer
@end example

@noindent
or else

@example
C-u C-c C-e C-b
@end example

@noindent
When you do this, Texinfo will not split the file and will not create
a tag table for it.
@cindex Making a tag table manually
@cindex Tag table, making manually

@node Tagifying
@subsection Tagifying a File

After creating an unsplit Info file, you must create a tag table for
it.  Visit the Info file you wish to tagify and type:

@example
M-x Info-tagify
@end example

@noindent
(Note the uppercase @samp{I} in @code{Info-tagify}.)  This creates an
Info file with a tag table that you can validate.

The third step is to validate the Info file:

@example
M-x Info-validate
@end example

@noindent
(Note the uppercase @samp{I} in @code{Info-validate}.)
In brief, the steps are:

@example
@group
C-u M-x texinfo-format-buffer
M-x Info-tagify
M-x Info-validate
@end group
@end example

After you have validated the node structure, you can rerun
@code{texinfo-format-buffer} in the normal way so it will construct a
tag table and split the file automatically, or you can make the tag
table and split the file manually.

@node Splitting
@subsection Splitting a File Manually
@cindex Splitting an Info file manually
@cindex Info file, splitting manually

You should split a large file or else let the
@code{texinfo-format-buffer} or @code{makeinfo-buffer} command do it
for you automatically.  (Generally you will let one of the formatting
commands do this job for you.  @xref{Creating an Info File}.)

The split-off files are called the indirect subfiles.

Info files are split to save memory.  With smaller files, Emacs does not
have make such a large buffer to hold the information.

If an Info file has more than 30 nodes, you should also make a tag
table for it.  @xref{Using @code{Info-validate}}, for information
about creating a tag table.  (Again, tag tables are usually created
automatically by the formatting command; you only need to create a tag
table yourself if you are doing the job manually.  Most likely, you
will do this for a large, unsplit file on which you have run
@code{Info-validate}.)

Visit the Info file you wish to tagify and split and type the two
commands:

@example
M-x Info-tagify
M-x Info-split
@end example

@noindent
(Note that the @samp{I} in @samp{Info} is uppercase.)

When you use the @code{Info-split} command, the buffer is modified into a
(small) Info file which lists the indirect subfiles.  This file should be
saved in place of the original visited file.  The indirect subfiles are
written in the same directory the original file is in, with names generated
by appending @samp{-} and a number to the original file name.

The primary file still functions as an Info file, but it contains just
the tag table and a directory of subfiles.

@node Info Format Specification
@appendix Info Format Specification

@cindex Info format specification
@cindex Specification of Info format
@cindex Definition of Info format

Here we describe the technical details of the Info format.

In this formal description, the characters @code{<>*()|=#} are used
for the language of the description itself.  Other characters are
literal.  The formal constructs used are typical: @code{<...>}
indicates a metavariable name, @samp{=} means definition, @samp{*}
repetition, @samp{?} optional, @samp{()} grouping, @samp{|}
alternation, @samp{#} comment.  Exception: @samp{*} at the beginning
of a line is literal.

In general, programs that read Info files should try to be
case-insensitive to keywords that occur in the file (for example,
@samp{Tag Table} and @samp{Tag table} should be equivalent) in order to
support Info-generating programs that use different capitalization.

The sections in an Info file (such as nodes or tag tables) are separated
with a sequence:

@example
(^L)?^_(^L)?^J
@end example

@noindent
That is, a @samp{CTRL-_} character followed by a newline, with optional
formfeed characters.  We refer to such sequences as @t{<separator>}.

We specify literal parentheses (those that are part of the Info
format) with @t{<lparen>} and @t{<rparen>}, meaning the single
characters @samp{(} and @samp{)} respectively.  We specify the
@samp{CTRL-?} character (character number 127) @t{<del>}.  Finally,
the two-character sequence @samp{^@var{x}} means the single
character @samp{CTRL-@var{x}}, for any @var{x}.

This format definition was written some 25 years after the Info format
was first devised.  So in the event of conflicts between this
definition and actual practice, practice wins.  It also assumes some
general knowledge of Texinfo; it is meant to be a guide for
implementors rather than a rigid technical standard.  We often refer
back to other parts of this manual for examples and definitions,
rather than redundantly spelling out every detail.

@menu
* General: Info Format General Layout.
* Text:    Info Format Text Constructs.
@end menu

@node Info Format General Layout
@section Info Format General Layout

This section describes the overall layout of Info manuals.

@menu
* Whole:           Info Format Whole Manual. Split vs.@: nonsplit manuals.
* Preamble:        Info Format Preamble.
* Indirect:        Info Format Indirect Table.
* Tag table:       Info Format Tag Table.
* Local variables: Info Format Local Variables.
* Regular nodes:   Info Format Regular Nodes.
@end menu

@node Info Format Whole Manual
@subheading Info Format: A Whole Manual

@cindex Nonsplit manuals, Info format of
@cindex Split manuals, Info format of
@cindex Whole manual, in Info format

To begin, an Info manual is either @dfn{nonsplit} (contained wholly
within a single file) or @dfn{split} (across several files).

The syntax for a nonsplit manual is:

@example
    <nonsplit info file> =
<preamble>
<node>*
<tag table>?
<local variables>?
@end example

When split, there is a @dfn{main file}, which contains only pointers
to the nodes given in other @dfn{subfiles}.  The main file looks
like this:

@example
    <split info main file> =
<preamble>
<indirect table>
<tag table>
<local variables>?
@end example

The subfiles in a split manual have the following syntax:

@example
    <split info subfile> =
<preamble>
<node>*
@end example

Note that the tag table is not optional for split files, as it is used
with the indirect table to deduce which subfile a particular node is in.

@node Info Format Preamble
@subheading Info Format: Preamble

@cindex Preamble, in Info format

The @t{<preamble>} is text at the beginning of all output files.
It is not intended to be visible by default in an Info viewer, but
may be displayed upon user request.

@example
    <preamble> =
<identification>       # "This is FILENAME, produced by ..."
<copying text>         # Expansion of @@copying text.
<dir entries>          # Derived from @@dircategory and @@direntry.
@end example

@noindent
These pieces are:

@table @t
@item <identification line>
An arbitrary string beginning the output file, followed by a blank
line.

@item <copying text>
The expansion of a @code{@@copying} environment, if the manual has
one (@pxref{@code{@@copying}}).

@item <dir entries>
The result of any @code{@@dircategory} and @code{@@direntry}
commands present in the manual (@pxref{Installing Dir Entries}).

@end table

@node Info Format Indirect Table
@subheading Info Format: Indirect Table

@cindex Indirect table, in Info format

@example
    <indirect table> =
<separator>
Indirect:
(<filename>: <bytepos>)*
@end example

The indirect table is written to the main file in the case of split
output only.  It specifies, as a decimal integer, the starting byte
position (zero-based) that the first node of each subfile would have if
the subfiles were concatenated together in order, not including the
top-level file.  The first node of actual content is pointed to by the
first entry.

As an example, suppose split output is generated for the GDB manual.
The top-level file @file{gdb.info} will contain something like this:

@example
<separator>
Indirect:
gdb.info-1: 1878
gdb.info-2: 295733
...
@end example

This tells Info viewers that the first node of the manual occurs at
byte 1878 of the file @file{gdb.info-1} (which would be after that file's
preamble.)  The first node in the @file{gdb.info-2} subfile would start at
byte 295733 if @file{gdb.info-2} were appended to @file{gdb.info-1},
including any preamble sections in both files.

Unfortunately, Info-creating programs such as @code{makeinfo} have not
always implemented these rules perfectly, due to various bugs and
oversights.  Therefore, robust Info viewers should fall back to
searching ``nearby'' the given position for a node, instead of
giving up immediately if the position is not exactly at a node beginning.

@node Info Format Tag Table
@subheading Info Format: Tag Table

@cindex Tag table, in Info format

@example
    <tag table> =
<separator>
Tag Table:
(<lparen>Indirect<rparen>)?
(Node|Ref): <nodeid>^?<bytepos>
<separator>
End Tag Table
@end example

The @samp{(Indirect)} line appears in the case of split output only.

The tag table specifies the starting byte position of each node and anchor
in the file.  In the case of split output, it is only written in the main
output file.

Each line defines an identifier as either an anchor or a node, as
specified.  For example, @samp{Node: Top^?1647} says that the node named
@samp{Top} starts at byte 1647 while @samp{Ref: Overview-Footnote-1^?30045}
says that the anchor named @samp{Overview-Footnote-1} starts at byte 30045.
It is an error to define the same identifier both ways.

In the case of nonsplit output, the byte positions simply refer to the
location in the output file.  In the case of split output, the byte
positions refer to an imaginary file created by concatenating all the
split files (but not the top-level file).  See the previous section.

Here is an example:

@example
^_
Tag Table:
Node: Top^?89
Node: Ch1^?292
^_
End Tag Table
@end example

@noindent
This specifies a manual with two nodes, `Top' and `Ch1', at byte
positions 89 and 292 respectively.  Because the @samp{(Indirect)} line
is not present, the manual is not split.

Preamble sections or other non-node sections of files do not have a tag
table entry.

@node Info Format Local Variables
@subheading Info Format: Local Variables

@cindex Local variable section, in Info format

The local variables section is optional and is currently used to give the
encoding information.  It may be augmented in the future.

@example
    <local variables> =
<separator>
Local Variables:
coding: <encoding>
End:
@end example

@xref{@code{@@documentencoding}}.

@node Info Format Regular Nodes
@subheading Info Format: Regular Nodes

@cindex Info nodes, in Info format

Regular nodes look like this:

@example
    <node> =
<separator>
File: <fn>, Node: <id1>, (Next: <id2>, )? (Prev: <id3>, )? Up: <id4>

<general text, until the next ^_ or end-of-file>
@end example

@noindent
At least one space or tab must be present after each colon and comma,
but any number of spaces are ignored.  The @t{<id>} node identifiers have
following format:

@example
   <id> = (<lparen><infofile><rparen>)?(<del>?<nodename><del>?)?
|  <id> = (<lparen><infofile><rparen>)?(<nodename>)?
@end example

This @t{<node>} defines @t{<id1>} in file @t{<fn>}, which is typically
either @samp{manualname} or @samp{manualname.info}.  No parenthesized
@t{<infofile>} component may appear within @t{<id1>}.

Each of the identifiers after @code{Next}, @code{Prev} and @code{Up}
refer to nodes or anchors within a file.  These pointers normally
refer within the same file, but @samp{(dir)} is often used to point to
the top-level dir file.  If an @t{<infofile>} component is used then
the node name may be omitted, in which case the node identifier refers
to the @samp{Top} node within the referenced file.

The @code{Next} and @code{Prev} pointers are optional.  The @code{Up}
pointer is technically also optional, although most likely this
indicates a mistake in the node structuring.  Conventionally, the
nodes are arranged to form a tree, but this is not a requirement of
the format.

Node names containing periods, commas, colons or parentheses
(including @@-commands which produce any of these) can confuse
Info readers.
If it is necessary to refer to a node whose name contains any of
these, the @t{<nodename>} should be surrounded by a pair of @t{<del>}
characters.  There is support in @command{makeinfo} for adding these
characters (@pxref{INFO_SPECIAL_CHARS_QUOTE}); however, we don't
recommend you make use of this support until such time as Info-reading
programs that recognize this syntax are common.  @xref{Node Line
Requirements}.

The use of non-ASCII characters in the names of nodes is permitted,
but can cause problems in cross-references between nodes in Info files
with different character encodings, and also when node names from many
different files are listed (for example, with the @option{--apropos}
option to the standalone Info browser), so we recommend avoiding them
whenever feasible.  For example, prefer the use of the ASCII
apostrophe character (@t{'}) to Unicode directional quotes.

The @t{<general text>} of the node can include the special constructs
described next.

@node Info Format Text Constructs
@section Info Format Text Constructs

@cindex Info format text constructs
@cindex text constructs, Info format

These special Info constructs can appear within the text of a node.

@node Info Format Menu
@subsection Info Format: Menu

@cindex Menus, in Info format

Conventionally menus appear at the end of nodes, but the Info format
places no restrictions on their location.

@example
    <menu> =
* Menu:
(<menu entry> | <menu comment>)*
@end example

The parts of a @t{<menu entry>} are also described in @ref{Menu
Parts}.  They have the same syntax as cross-references (@pxref{Info
Format Cross Reference}).  Indices extend the menu format to specify the
destination line; @pxref{Info Format Printindex}.

A @t{<menu comment>} is any line not beginning with @samp{*} that
appears either at the beginning of the menu or is separated from a
menu entry by one or more blank lines.  These comments are intended to
be displayed as part of the menu, as-is (@pxref{Writing a Menu}).

@node Info Format Image
@subsection Info Format: Image

@cindex Images, in Info format

The @code{@@image} command results in the following special directive
within the Info file (@pxref{Images}):

@example
    <image> =
^@@^H[image src="<image file>"
            (text="<txt file contents>")?
            (alt="<alt text>")?
^@@^H]
@end example

The line breaks and indentation in this description are editorial; the
whitespace between the different parts of the directive in Info files
is arbitrary.

In the strings @t{<image file>}, @t{<txt file contents>} and @t{<alt
text>}, @samp{"} is quoted as @samp{\"} and @samp{\} is quoted as
@samp{\\}.  The txt and alt specifications are optional.

The @t{alt} value serves the same purpose as in HTML: A prose
description of the image.  In text-only displays or speech systems,
for example, the @t{alt} value may be used instead of displaying the
(typically graphical) @t{<image file>}.

The @t{<txt file contents>}, if present, should be taken as an ASCII
representation of the image, for possible use on a text-only display.

The format does not prescribe the choice between displaying the
@t{<image file>}, the @t{<alt text>} or the @t{<txt file contents>}.

@node Info Format Printindex
@subsection Info Format: Printindex

@cindex Indices, in Info format

Indices in Info format are generally written as a menu
(@pxref{Indices}), but with an additional directive at the beginning
marking this as an index node:

@example
    <printindex> =
^@@^H[index^@@^H]
* Menu:

<index entry>*
@end example

The @t{<index entry>} items are similar to normal menu entries, but
the free-format description is replaced by the line number of where
the entries occurs in the text:

@example
    <index entry> =
* <entry text>: <entry node>. <lparen>line <lineno><rparen>
@end example

@noindent
The @t{<entry text>} is the index term.  The @t{<lineno>} is an
unsigned integer, given relative to the start of the @t{<entry node>}.
There may be arbitrary whitespace after the colon and period, as usual
in menus, and may be broken across lines.  Here is an example:

@example
^@@^H[index^@@^H]
* Menu:

* thunder:           Weather Phenomena.             (line 5)
@end example

This means that an index entry for `thunder' appears at line 5 of the
node `Weather Phenomena'.

@node Info Format Cross Reference
@subsection Info Format: Cross-reference

@cindex Cross-references, in Info format

A general cross-reference in Info format has one of the following two forms:

@example
    <cross-reference> =
  * (N|n)ote <id>::
@c| * (N|n)ote <label>:<id>(.|,)?
| * (N|n)ote <label>:<id>(.|,)

     <id> = (<lparen><infofile><rparen>)?(<del>?<nodename><del>?)?
|    <id> = (<lparen><infofile><rparen>)?(<nodename>)?
    <label> = <del>?<label text><del>?
@end example

No space should occur between the @samp{*} character and the following
@samp{N} or @samp{n}.  @samp{*Note} should be used at the start of a
sentence, otherwise @samp{*note} should be used.  (Some Info readers,
such as the one in Emacs, can display @samp{*Note} and @samp{*note} as
@samp{See} and @samp{see} respectively.) In both cases, @t{<label
text>} is descriptive text.

In both forms the @t{<id>} refers to a node or anchor, in the same way
as a reference in the node information line does (@pxref{Info Format
Regular Nodes}).  The optional parenthesized @samp{<infofile>} is the
filename of the manual being referenced, and the @t{<nodename>} is the
node or anchor within that manual,

The second form has a descriptive label.  A cross-reference in this form
should usually be terminated with a comma or period, to make it
feasible to find the end of the @t{<id>}.

If @t{<label>} contains a colon character (@t{:}), it should be
surrounded with a pair of @t{<del>} characters.  Likewise, if
@t{<nodename>} contains problematic characters (such as commas or
periods), it should be surrounded by a pair of @t{<del>} characters;
then a terminating comma or period is not needed.

As with node names, this quoting mechanism has as of the time of
writing limited support in Info-reading programs; hence we do not
recommend using it until this changes.

The format does not prescribe how to find other manuals to resolve
such references.

Here are some examples:

@example
*note GNU Free Documentation License::
*note Tag table: Info Format Tag Table, for details.
*Note Overview: (make)Top.
*Note ^?:^?: (bash)Bourne Shell Builtins.
*Note alloca.h: (gnulib)^?alloca.h^?.
@end example

The first shows a reference to a node in the current manual using the
short form.

The second also refers to a node in the current manual, namely `Info
Format Tag Table'; the `Tag table' before the @samp{:} is only a label
on this particular reference, and the @samp{for details.} is text
belonging to the sentence, not part of the reference.

The third example refers to the node `Top' in another manual, namely
@samp{make}, with `Overview' being the label for this cross-reference.

The fourth example shows a colon character being quoted in a label,
and the fifth example shows a period being quoted in a node name.

@xref{Cross References}.

@node GNU Free Documentation License
@appendix GNU Free Documentation License

@include fdl.texi

@node Command and Variable Index
@unnumbered Command and Variable Index

This is an alphabetical list of all the @@-commands, assorted Emacs Lisp
functions, and several variables.  To make the list easier to use, the
commands are listed without their preceding @samp{@@}.

@printindex fn

@node General Index
@unnumbered General Index

@printindex cp

@bye

repo_name: mthl/texinfo

license: mit