From: TjL <luomat@gmail.com>
To: "Benjamin R. Haskell" <zsh@benizi.com>
Cc: Zsh Users <zsh-users@zsh.org>
Subject: Re: equivalent of "if (( $+commands[FOO] ))" for functions?
Date: Mon, 6 Aug 2012 19:12:04 -0400 [thread overview]
Message-ID: <CAPHo7JfFg7D7_g6axSup1Y9pGBNR-3RZySc=qoGf9Cb+UjTMTA@mail.gmail.com> (raw)
In-Reply-To: <alpine.LNX.2.01.1208061823580.24430@hp.internal>
On Mon, Aug 6, 2012 at 6:38 PM, Benjamin R. Haskell <zsh@benizi.com> wrote:
> In case you've only seen the idiom you're using, and didn't have an
> explanation:
>
> $+param expands to 0 if param is unset, and 1 if it's set. The double
> parentheses: (( ... )) just make the conditional "mathy" (so that non-zero
> is true). So, you can use this with your own associative arrays, too:
>
> typeset -A some_array
> some_array+=( foo some-foo-thing )
> if (( $+some_array[foo] ))
> then
> echo yay
> fi
Ah, that's helpful, thanks. Indeed I have just been copy/pasting this
without really knowing how it worked.
Hrm… so… I often do something like this to do different things based
on the exit status of a given command 'foo'
For example:
foo
EXIT="$?"
if [ "$EXIT" = "0" ]
then
# do whatever
else
echo "$0: failed (\$EXIT = $EXIT)"
exit 1
fi
Is there a way to do something like that with $+param?
I tried this:
EXIT+=( test -d ~/etc )
if (( $+EXIT[test] ))
then
echo yes
else
echo no
fi
thinking that it would say 'yes' if 'test -d' exited with status = 0
or 'no' with any other status, but that didn't seem to work (I always
seem to get no even if 'test -d' should return 0.
So I assume that I'm misunderstanding something, possibly trying to
make apple pie uses oranges and wondering why it doesn't taste right.
TjL
next prev parent reply other threads:[~2012-08-06 23:12 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-08-06 22:13 TjL
2012-08-06 22:36 ` Frank Terbeck
2012-08-06 22:38 ` Benjamin R. Haskell
2012-08-06 23:12 ` TjL [this message]
2012-08-07 13:17 ` Benjamin R. Haskell
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