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Re: unset FOO


From: Peter Seebach
Subject: Re: unset FOO
Date: Tue, 14 Oct 2008 11:42:51 -0500

In message <address@hidden>, Eric Blake writes:
>Quotes won't help; the shell then tries to evaluate the command 'unset FOO' 
>with no arguments, because there is no reason to do IFS splitting.

Doh.

>But this works, using an intermediate variable, so that IFS splitting still 
>occurs:

>$ /bin/sh -c 'foo=a;tmp="unset foo";${foo+$tmp};echo ${foo+set}'; echo $?

>0
>$

Oh, that's neat.

>But why waste the time going through a temporary variable, when you can use:

>test ${foo+set} = set && unset foo

That is clearer, true.

-s




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