code:
;; popen emulation, for non-stdio based ports.

;;;; Copyright (C) 1998, 1999, 2000, 2001, 2003, 2006 Free Software Foundation, Inc.
;;;;
;;;; This library is free software; you can redistribute it and/or
;;;; modify it under the terms of the GNU Lesser General Public
;;;; License as published by the Free Software Foundation; either
;;;; version 2.1 of the License, or (at your option) any later version.
;;;;
;;;; This library is distributed in the hope that it will be useful,
;;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
;;;; Lesser General Public License for more details.
;;;;
;;;; You should have received a copy of the GNU Lesser General Public
;;;; License along with this library; if not, write to the Free Software
;;;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
;;;;

(define-module (ice-9 popen)
  :export (port/pid-table open-pipe* open-pipe close-pipe open-input-pipe
	   open-output-pipe open-input-output-pipe))

(define (make-rw-port read-port write-port)
  (make-soft-port
   (vector
    (lambda (c) (write-char c write-port))
    (lambda (s) (display s write-port))
    (lambda () (force-output write-port))
    (lambda () (read-char read-port))
    (lambda () (close-port read-port) (close-port write-port)))
   "r+"))

;; a guardian to ensure the cleanup is done correctly when
;; an open pipe is gc'd or a close-port is used.
(define pipe-guardian (make-guardian))

;; a weak hash-table to store the process ids.
(define port/pid-table (make-weak-key-hash-table 31))

(define (ensure-fdes port mode)
  (or (false-if-exception (fileno port))
      (open-fdes *null-device* mode)))

;; run a process connected to an input, an output or an
;; input/output port
;; mode: OPEN_READ, OPEN_WRITE or OPEN_BOTH
;; returns port/pid pair.
(define (open-process mode prog . args)
  (let* ((reading (or (equal? mode OPEN_READ)
		      (equal? mode OPEN_BOTH)))
	 (writing (or (equal? mode OPEN_WRITE)
		      (equal? mode OPEN_BOTH)))
	 (c2p (if reading (pipe) #f))  ; child to parent
	 (p2c (if writing (pipe) #f))) ; parent to child

    (if c2p (setvbuf (cdr c2p) _IONBF))
    (if p2c (setvbuf (cdr p2c) _IONBF))
    (let ((pid (primitive-fork)))
      (cond ((= pid 0)
	     ;; child
	     (set-batch-mode?! #t)

	     ;; select the three file descriptors to be used as
	     ;; standard descriptors 0, 1, 2 for the new
	     ;; process. They are pipes to/from the parent or taken
	     ;; from the current Scheme input/output/error ports if
	     ;; possible.

	     (let ((input-fdes (if writing
				   (fileno (car p2c))
				   (ensure-fdes (current-input-port)
						O_RDONLY)))
		   (output-fdes (if reading
				    (fileno (cdr c2p))
				    (ensure-fdes (current-output-port)
						 O_WRONLY)))
		   (error-fdes (ensure-fdes (current-error-port)
					    O_WRONLY)))

	       ;; close all file descriptors in ports inherited from
	       ;; the parent except for the three selected above.
	       ;; this is to avoid causing problems for other pipes in
	       ;; the parent.

	       ;; use low-level system calls, not close-port or the
	       ;; scsh routines, to avoid side-effects such as
	       ;; flushing port buffers or evicting ports.

	       (port-for-each (lambda (pt-entry)
				(false-if-exception
				 (let ((pt-fileno (fileno pt-entry)))
				   (if (not (or (= pt-fileno input-fdes)
						(= pt-fileno output-fdes)
						(= pt-fileno error-fdes)))
				       (close-fdes pt-fileno))))))

	       ;; Copy the three selected descriptors to the standard
	       ;; descriptors 0, 1, 2, if not already there

	       (cond ((not (= input-fdes 0))
		      (if (= output-fdes 0)
			  (set! output-fdes (dup->fdes 0)))
		      (if (= error-fdes 0)
			  (set! error-fdes (dup->fdes 0)))
		      (dup2 input-fdes 0)
		      ;; it's possible input-fdes is error-fdes
		      (if (not (= input-fdes error-fdes))
			  (close-fdes input-fdes))))

	       (cond ((not (= output-fdes 1))
		      (if (= error-fdes 1)
			  (set! error-fdes (dup->fdes 1)))
		      (dup2 output-fdes 1)
		      ;; it's possible output-fdes is error-fdes
		      (if (not (= output-fdes error-fdes))
			  (close-fdes output-fdes))))

	       (cond ((not (= error-fdes 2))
		      (dup2 error-fdes 2)
		      (close-fdes error-fdes)))

	       (apply execlp prog prog args)))

	    (else
	     ;; parent
	     (if c2p (close-port (cdr c2p)))
	     (if p2c (close-port (car p2c)))
	     (cons (cond ((not writing) (car c2p))
			 ((not reading) (cdr p2c))
			 (else (make-rw-port (car c2p)
					     (cdr p2c))))
		   pid))))))

(define (open-pipe* mode command . args)
  "Executes the program @var{command} with optional arguments
@var{args} (all strings) in a subprocess.
A port to the process (based on pipes) is created and returned.
@var{modes} specifies whether an input, an output or an input-output
port to the process is created: it should be the value of
@code{OPEN_READ}, @code{OPEN_WRITE} or @code{OPEN_BOTH}."
  (let* ((port/pid (apply open-process mode command args))
	 (port (car port/pid)))
    (pipe-guardian port)
    (hashq-set! port/pid-table port (cdr port/pid))
    port))

(define (open-pipe command mode)
  "Executes the shell command @var{command} (a string) in a subprocess.
A port to the process (based on pipes) is created and returned.
@var{modes} specifies whether an input, an output or an input-output
port to the process is created: it should be the value of
@code{OPEN_READ}, @code{OPEN_WRITE} or @code{OPEN_BOTH}."
  (open-pipe* mode "/bin/sh" "-c" command))

(define (fetch-pid port)
  (let ((pid (hashq-ref port/pid-table port)))
    (hashq-remove! port/pid-table port)
    pid))

(define (close-process port/pid)
  (close-port (car port/pid))
  (cdr (waitpid (cdr port/pid))))

;; for the background cleanup handler: just clean up without reporting
;; errors.  also avoids blocking the process: if the child isn't ready
;; to be collected, puts it back into the guardian's live list so it
;; can be tried again the next time the cleanup runs.
(define (close-process-quietly port/pid)
  (catch 'system-error
	 (lambda ()
	   (close-port (car port/pid)))
	 (lambda args #f))
  (catch 'system-error
	 (lambda ()
	   (let ((pid/status (waitpid (cdr port/pid) WNOHANG)))
	     (cond ((= (car pid/status) 0)
		    ;; not ready for collection
		    (pipe-guardian (car port/pid))
		    (hashq-set! port/pid-table
				(car port/pid) (cdr port/pid))))))
	 (lambda args #f)))

(define (close-pipe p)
  "Closes the pipe created by @code{open-pipe}, then waits for the process
to terminate and returns its status value, @xref{Processes, waitpid}, for
information on how to interpret this value."
  (let ((pid (fetch-pid p)))
    (if (not pid)
        (error "close-pipe: pipe not in table"))
    (close-process (cons p pid))))

(define reap-pipes
  (lambda ()
    (let loop ((p (pipe-guardian)))
      (cond (p
	     ;; maybe removed already by close-pipe.
	     (let ((pid (fetch-pid p)))
	       (if pid
		   (close-process-quietly (cons p pid))))
	     (loop (pipe-guardian)))))))

(add-hook! after-gc-hook reap-pipes)

(define (open-input-pipe command)
  "Equivalent to @code{open-pipe} with mode @code{OPEN_READ}"
  (open-pipe command OPEN_READ))

(define (open-output-pipe command)
  "Equivalent to @code{open-pipe} with mode @code{OPEN_WRITE}"
  (open-pipe command OPEN_WRITE))

(define (open-input-output-pipe command)
  "Equivalent to @code{open-pipe} with mode @code{OPEN_BOTH}"
  (open-pipe command OPEN_BOTH))


code:
;;; installed-scm-file

;;;; Copyright (C) 1999, 2006 Free Software Foundation, Inc.
;;;;
;;;; This library is free software; you can redistribute it and/or
;;;; modify it under the terms of the GNU Lesser General Public
;;;; License as published by the Free Software Foundation; either
;;;; version 2.1 of the License, or (at your option) any later version.
;;;;
;;;; This library is distributed in the hope that it will be useful,
;;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
;;;; Lesser General Public License for more details.
;;;;
;;;; You should have received a copy of the GNU Lesser General Public
;;;; License along with this library; if not, write to the Free Software
;;;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
;;;;

(define (stat:dev f) (vector-ref f 0))
(define (stat:ino f) (vector-ref f 1))
(define (stat:mode f) (vector-ref f 2))
(define (stat:nlink f) (vector-ref f 3))
(define (stat:uid f) (vector-ref f 4))
(define (stat:gid f) (vector-ref f 5))
(define (stat:rdev f) (vector-ref f 6))
(define (stat:size f) (vector-ref f 7))
(define (stat:atime f) (vector-ref f 8))
(define (stat:mtime f) (vector-ref f 9))
(define (stat:ctime f) (vector-ref f 10))
(define (stat:blksize f) (vector-ref f 11))
(define (stat:blocks f) (vector-ref f 12))

;; derived from stat mode.
(define (stat:type f) (vector-ref f 13))
(define (stat:perms f) (vector-ref f 14))

(define (passwd:name obj) (vector-ref obj 0))
(define (passwd:passwd obj) (vector-ref obj 1))
(define (passwd:uid obj) (vector-ref obj 2))
(define (passwd:gid obj) (vector-ref obj 3))
(define (passwd:gecos obj) (vector-ref obj 4))
(define (passwd:dir obj) (vector-ref obj 5))
(define (passwd:shell obj) (vector-ref obj 6))

(define (group:name obj) (vector-ref obj 0))
(define (group:passwd obj) (vector-ref obj 1))
(define (group:gid obj) (vector-ref obj 2))
(define (group:mem obj) (vector-ref obj 3))

(define (utsname:sysname obj) (vector-ref obj 0))
(define (utsname:nodename obj) (vector-ref obj 1))
(define (utsname:release obj) (vector-ref obj 2))
(define (utsname:version obj) (vector-ref obj 3))
(define (utsname:machine obj) (vector-ref obj 4))

(define (getpwent) (getpw))
(define (setpwent) (setpw #t))
(define (endpwent) (setpw))

(define (getpwnam name) (getpw name))
(define (getpwuid uid) (getpw uid))

(define (getgrent) (getgr))
(define (setgrent) (setgr #t))
(define (endgrent) (setgr))

(define (getgrnam name) (getgr name))
(define (getgrgid id) (getgr id))

license: unknown


code:
;;;; -*-scheme-*-
;;;;
;;;; 	Copyright (C) 2001, 2004, 2006 Free Software Foundation, Inc.
;;;;
;;;; This library is free software; you can redistribute it and/or
;;;; modify it under the terms of the GNU Lesser General Public
;;;; License as published by the Free Software Foundation; either
;;;; version 2.1 of the License, or (at your option) any later version.
;;;;
;;;; This library is distributed in the hope that it will be useful,
;;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
;;;; Lesser General Public License for more details.
;;;;
;;;; You should have received a copy of the GNU Lesser General Public
;;;; License along with this library; if not, write to the Free Software
;;;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
;;;;
(define-module (ice-9 pretty-print)
  :use-module (ice-9 optargs)
  :export (pretty-print))

;; From SLIB.

;;"genwrite.scm" generic write used by pretty-print and truncated-print.
;; Copyright (c) 1991, Marc Feeley
;; Author: Marc Feeley (feeley@iro.umontreal.ca)
;; Distribution restrictions: none

(define genwrite:newline-str (make-string 1 #\newline))

(define (generic-write obj display? width per-line-prefix output)

  (define (read-macro? l)
    (define (length1? l) (and (pair? l) (null? (cdr l))))
    (let ((head (car l)) (tail (cdr l)))
      (case head
        ((quote quasiquote unquote unquote-splicing) (length1? tail))
        (else                                        #f))))

  (define (read-macro-body l)
    (cadr l))

  (define (read-macro-prefix l)
    (let ((head (car l)))
      (case head
        ((quote)            "'")
        ((quasiquote)       "`")
        ((unquote)          ",")
        ((unquote-splicing) ",@"))))

  (define (out str col)
    (and col (output str) (+ col (string-length str))))

  (define (wr obj col)
    (cond ((and (pair? obj)
		(read-macro? obj))
	   (wr (read-macro-body obj)
	       (out (read-macro-prefix obj) col)))
	  (else
	   (out (object->string obj (if display? display write)) col))))

  (define (pp obj col)

    (define (spaces n col)
      (if (> n 0)
        (if (> n 7)
          (spaces (- n 8) (out "        " col))
          (out (substring "        " 0 n) col))
        col))

    (define (indent to col)
      (and col
           (if (< to col)
             (and (out genwrite:newline-str col)
		  (out per-line-prefix 0)
		  (spaces to 0))
             (spaces (- to col) col))))

    (define (pr obj col extra pp-pair)
      (if (or (pair? obj) (vector? obj)) ; may have to split on multiple lines
        (let ((result '())
              (left (min (+ (- (- width col) extra) 1) max-expr-width)))
          (generic-write obj display? #f ""
            (lambda (str)
              (set! result (cons str result))
              (set! left (- left (string-length str)))
              (> left 0)))
          (if (> left 0) ; all can be printed on one line
            (out (reverse-string-append result) col)
            (if (pair? obj)
              (pp-pair obj col extra)
              (pp-list (vector->list obj) (out "#" col) extra pp-expr))))
        (wr obj col)))

    (define (pp-expr expr col extra)
      (if (read-macro? expr)
        (pr (read-macro-body expr)
            (out (read-macro-prefix expr) col)
            extra
            pp-expr)
        (let ((head (car expr)))
          (if (symbol? head)
            (let ((proc (style head)))
              (if proc
                (proc expr col extra)
                (if (> (string-length (symbol->string head))
                       max-call-head-width)
                  (pp-general expr col extra #f #f #f pp-expr)
                  (pp-call expr col extra pp-expr))))
            (pp-list expr col extra pp-expr)))))

    ; (head item1
    ;       item2
    ;       item3)
    (define (pp-call expr col extra pp-item)
      (let ((col* (wr (car expr) (out "(" col))))
        (and col
             (pp-down (cdr expr) col* (+ col* 1) extra pp-item))))

    ; (item1
    ;  item2
    ;  item3)
    (define (pp-list l col extra pp-item)
      (let ((col (out "(" col)))
        (pp-down l col col extra pp-item)))

    (define (pp-down l col1 col2 extra pp-item)
      (let loop ((l l) (col col1))
        (and col
             (cond ((pair? l)
                    (let ((rest (cdr l)))
                      (let ((extra (if (null? rest) (+ extra 1) 0)))
                        (loop rest
                              (pr (car l) (indent col2 col) extra pp-item)))))
                   ((null? l)
                    (out ")" col))
                   (else
                    (out ")"
                         (pr l
                             (indent col2 (out "." (indent col2 col)))
                             (+ extra 1)
                             pp-item)))))))

    (define (pp-general expr col extra named? pp-1 pp-2 pp-3)

      (define (tail1 rest col1 col2 col3)
        (if (and pp-1 (pair? rest))
          (let* ((val1 (car rest))
                 (rest (cdr rest))
                 (extra (if (null? rest) (+ extra 1) 0)))
            (tail2 rest col1 (pr val1 (indent col3 col2) extra pp-1) col3))
          (tail2 rest col1 col2 col3)))

      (define (tail2 rest col1 col2 col3)
        (if (and pp-2 (pair? rest))
          (let* ((val1 (car rest))
                 (rest (cdr rest))
                 (extra (if (null? rest) (+ extra 1) 0)))
            (tail3 rest col1 (pr val1 (indent col3 col2) extra pp-2)))
          (tail3 rest col1 col2)))

      (define (tail3 rest col1 col2)
        (pp-down rest col2 col1 extra pp-3))

      (let* ((head (car expr))
             (rest (cdr expr))
             (col* (wr head (out "(" col))))
        (if (and named? (pair? rest))
          (let* ((name (car rest))
                 (rest (cdr rest))
                 (col** (wr name (out " " col*))))
            (tail1 rest (+ col indent-general) col** (+ col** 1)))
          (tail1 rest (+ col indent-general) col* (+ col* 1)))))

    (define (pp-expr-list l col extra)
      (pp-list l col extra pp-expr))

    (define (pp-LAMBDA expr col extra)
      (pp-general expr col extra #f pp-expr-list #f pp-expr))

    (define (pp-IF expr col extra)
      (pp-general expr col extra #f pp-expr #f pp-expr))

    (define (pp-COND expr col extra)
      (pp-call expr col extra pp-expr-list))

    (define (pp-CASE expr col extra)
      (pp-general expr col extra #f pp-expr #f pp-expr-list))

    (define (pp-AND expr col extra)
      (pp-call expr col extra pp-expr))

    (define (pp-LET expr col extra)
      (let* ((rest (cdr expr))
             (named? (and (pair? rest) (symbol? (car rest)))))
        (pp-general expr col extra named? pp-expr-list #f pp-expr)))

    (define (pp-BEGIN expr col extra)
      (pp-general expr col extra #f #f #f pp-expr))

    (define (pp-DO expr col extra)
      (pp-general expr col extra #f pp-expr-list pp-expr-list pp-expr))

    ; define formatting style (change these to suit your style)

    (define indent-general 2)

    (define max-call-head-width 5)

    (define max-expr-width 50)

    (define (style head)
      (case head
        ((lambda let* letrec define) pp-LAMBDA)
        ((if set!)                   pp-IF)
        ((cond)                      pp-COND)
        ((case)                      pp-CASE)
        ((and or)                    pp-AND)
        ((let)                       pp-LET)
        ((begin)                     pp-BEGIN)
        ((do)                        pp-DO)
        (else                        #f)))

    (pr obj col 0 pp-expr))

  (out per-line-prefix 0)
  (if width
    (out genwrite:newline-str (pp obj 0))
    (wr obj 0))
  ;; Return `unspecified'
  (if #f #f))

; (reverse-string-append l) = (apply string-append (reverse l))

(define (reverse-string-append l)

  (define (rev-string-append l i)
    (if (pair? l)
      (let* ((str (car l))
             (len (string-length str))
             (result (rev-string-append (cdr l) (+ i len))))
        (let loop ((j 0) (k (- (- (string-length result) i) len)))
          (if (< j len)
            (begin
              (string-set! result k (string-ref str j))
              (loop (+ j 1) (+ k 1)))
            result)))
      (make-string i)))

  (rev-string-append l 0))

(define (pretty-print obj . opts)
  "Pretty-print OBJ on PORT, which is a keyword argument defaulting to
the current output port.  Formatting can be controlled by a number of
keyword arguments: Each line in the output is preceded by the string
PER-LINE-PREFIX, which is empty by default.  The output lines will be
at most WIDTH characters wide; the default is 79.  If DISPLAY? is
true, display rather than write representation will be used.

Instead of with a keyword argument, you can also specify the output
port directly after OBJ, like (pretty-print OBJ PORT)."
  (if (pair? opts)
      (if (keyword? (car opts))
	  (apply pretty-print-with-keys obj opts)
	  (apply pretty-print-with-keys obj #:port (car opts) (cdr opts)))
      (pretty-print-with-keys obj)))

(define* (pretty-print-with-keys obj
				 #:key
				 (port (current-output-port))
				 (width 79)
				 (display? #f)
				 (per-line-prefix ""))
  (generic-write obj display?
		 (- width (string-length per-line-prefix))
		 per-line-prefix
		 (lambda (s) (display s port) #t)))