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Re: [PLUG] Distinguishing between environment variable with null value and one that is not set
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On Tue, Oct 13, 2009 at 5:19 PM, Paul L. Snyder <plsnyder@drexel.edu> wrote:
[KSB] <...snip...>
> How about this, which should be POSIX-compliant (and doesn't require a
> subshell):
>
> % foo=bar
> % if [[ -z ${foo+isset} ]]; then echo nope; else echo yep; fi
> yep
> % foo=''
> % if [[ -z ${foo+isset} ]]; then echo nope; else echo yep; fi
> yep
> % unset foo
> % if [[ -z ${foo+isset} ]]; then echo nope; else echo yep; fi
> nope
>
> 'isset' doesn't matter, it could be any non-zero-length string.
[KSB] That's perfect, Paul. I needed something to run in busybox
(Tiny Core Linux) as well as bash. Thank you very much.
Regards
-- Bhaskar
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