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From: ericblake AT comcast DOT net (Eric Blake)
To: yann DOT dubost AT capgemini DOT com, cygwin AT cygwin DOT com
Cc: Yann Dubost <yann DOT dubost AT capgemini DOT com>
Subject: Re: eval function not working anymore !?
Date: Thu, 15 Sep 2005 15:39:38 +0000
Message-Id: <091520051539.175.432995BA0004CE76000000AF22007340760A050E040D0C079D0A@comcast.net>

> 
> Hello,
> 
>  I have been using cygwin for several years now and I have several scripts
> tant do not work anymore since I installed the latest release of cygwin
> (doxnloaded last week).
> The reason is the eval function that I use quite a lot in such ways as :

eval is not a function, but a builtin.

> 
> DOMAINE_LISTE="DOM1 DOM2 DOM3"
> DOM1_MODULES='D1_M1 D1_M2"

Well, I hope that was a copy-n-pasto, because otherwise it
would never work with mismatched quotes.

> DOM2_MODULES="D2_M1 D2_M2"
> 
> for domain in $DOMAINE_LISTE
> do
>    eval MODULES=$"${domain}_MODULES"
>    ...
> done
> 
> Before it was working fine, but now echo $MODULES returns "DOM1_MODULES" or
> "DOM2_MODULES" instead of "D1_M1 D1_M2" "D2_M1 D2_M2"
> 
> Have you experience such a change ? 
> Do you have an idea why ?

Yes - sh is now bash, and bash has a POSIX-allowed extension
where $"  " has special meaning for purposes of string translation
($" is undefined by POSIX, and unimplemented by ash, so you
were lucky before).

> How can I work around this problem (another function to use ?)

Option 1: Fix your shell script to use POSIX compliant expressions
(basically, $" is non-portable in the first level of evaluation, so
quote the $ so that the second level of evaluation will see the
desired $DOM1_MODULES).  Any of the following properly quotes
the leading $ (and there are other ways, too):
eval MODULES=\$"${domain}_MODULES"
eval MODULES="\$${domain}_MODULES"
eval MODULES='$'"${domain}"_MODULES

Option 2: Disable the bash extension in your script:
shopt -u extquote

--
Eric Blake
volunteer cygwin bash maintainer



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