From Kurt.Hornik at wu.ac.at  Mon Dec 18 20:23:58 2017
From: Kurt.Hornik at wu.ac.at (Kurt Hornik)
Date: Mon, 18 Dec 2017 20:23:58 +0100
Subject: [Rd] Dialect for shell scripts
In-Reply-To: <CALEXWq0qHBLYL15ikSiSCOmOh1wLMnrArT=7o0xbxMhDeJ2Pqw@mail.gmail.com>
References: <98ab029a-fbbc-8297-b2e7-63857c43932f@icrar.org>
 <CALEXWq0qHBLYL15ikSiSCOmOh1wLMnrArT=7o0xbxMhDeJ2Pqw@mail.gmail.com>
Message-ID: <23096.5582.934560.295269@hornik.net>

>>>>> I?aki ?car writes:

Same from here: in addition to what the standards say, it always pays to
be defensive and check "Portable Shell Programming" in the Autoconf
manual.  Among other things, this says

'$((EXPRESSION))'
     Arithmetic expansion is not portable as some shells (most notably
     Solaris 10 '/bin/sh') don't support it.

motivating the code shown below.  Perhaps simplest to always use expr.

-k


> For what it's worth, Autoconf does not assume that arithmetic
> expansion will be available. Instead, it emits the following shell
> code:

> if ( eval 'test $(( 1 + 1 )) = 2' ) 2>/dev/null; then
>   eval 'func_arith ()
>   {
>     func_arith_result=$(( $* ))
>   }'
> else
>   func_arith ()
>   {
>     func_arith_result=`expr "$@"`
>   }
> fi

> 2017-12-17 23:55 GMT+01:00 Rodrigo Tobar <rtobar at icrar.org>:
>> Dear all,
>> 
>> During a recent package submission, we were highlighted that some lines in
>> our configure script didn't follow the correct syntax. The lines looked like
>> this:
>> 
>> x=$(($y/10))
>> 
>> We were indicated at the time that this is because the statement does not
>> use Bourne shell syntax, which is absolutely true, and also that the manual
>> warns about this, which is true again. So far everything is clear.
>> 
>> However, what confuses me is that even when the manual says that "you can
>> include an executable (Bourne) shell script configure in your package" [1],
>> the associated footnote says something slightly different: "The script
>> should only assume a POSIX-compliant /bin/sh" [2]. The footnote goes even
>> further, and links to the POSIX specification of the Shell Command Language
>> [3] (as published by The Open Group), which explicitly includes arithmetic
>> expressions like the one above in its syntax [4].
>> 
>> My question then is: what exact dialect should be considered? Given that the
>> statement above does not work in the Bourne shell, I conclude that the
>> Bourne shell is not POSIX-compliant. That in turn would make the manual
>> ambiguous as to the precise dialect that should be used by our configure
>> scripts, and either the shells used by R should be changed to be
>> POSIX-compliants, or the manual edited to be more precise regarding .
>> 
>> Many thanks.
>> 
>> Rodrigo
>> 
>> [1]
>> https://cran.r-project.org/doc/manuals/r-release/R-exts.html#Configure-and-cleanup
>> [2] https://cran.r-project.org/doc/manuals/r-release/R-exts.html#FOOT25
>> [3] http://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html
>> [4]
>> http://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_06_04
>> 
>> ______________________________________________
>> R-devel at r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-devel



> -- 
> I?aki ?car
> http://www.enchufa2.es
> @Enchufa2

> ______________________________________________
> R-devel at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel



[Rd] Dialect for shell scripts
Kurt Hornik