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To: "cygwin AT cygwin DOT com" <cygwin AT cygwin DOT com>
Subject: Re: Can't set variables in a while loop that is passed to the rest of  the script.
References: <EDF49EC9787F914CA157FF6927D65A88302633AB82 AT CBMCC-X7-MBX10 DOT ad DOT cibc DOT com> <4B4FAB5D DOT 4000106 AT bopp DOT net>
Date: Fri, 15 Jan 2010 02:39:12 +0100
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From: "Matthias Andree" <matthias DOT andree AT gmx DOT de>
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Am 15.01.2010, 00:40 Uhr, schrieb Jeremy Bopp <jeremy AT bopp DOT net>:

> On 1/14/2010 5:23 PM, Damo, David wrote:
>> Hi,
>>
>> I have fixed the problem. It seems in cygwin it spawns a subshell even  
>> under bash. I used a for loop instead and everything worked nicely.
>>
>> for line in `sed 's/\$/^/g' $propfile`
>> do
>> 	nvpair=$(echo $line | awk -F"=" '{print $1,$2}')
>> 	set -- $nvpair
>> 	if [ ! "$1" = ""  ]; then
>> 		eval "$1"=\"$2\"
>> 	fi
>> done
>
> Interesting.  Your workaround should work fine as long as the propfile
> is not too large, I think.  However, wouldn't it be easier to source a
> properly massaged version of propfile instead?

The observed behaviour ("sed ... | while read foo" not setting variables  
properly) is expected and documented, because the commands in a pipe will  
be launched in a subshell (per POSIX), where "in the current shell" is an  
exception you cannot rely on - as observed.
See IEEE Std 1003.1-2008, Shell & Utilities, Shell Command Language, 2.12  
Shell Execution Environment (near the end of the section).

I'd consider using the for line a fix, rather than a workaround.

I'd also recommend a good portion of caution when sourcing generated  
files. This all too easily becomes a major security concern unless  
combined with thorough error checking. "set -e" is a bare necessity, and  
security isn't halfway complete there...

-- 
Matthias Andree

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