From: Aaron Davies <agdavi01@louisville.edu>
To: zsh-users@sunsite.dk
Subject: Re: Slightly OT: Error-Handling in a Pipeline, preferably non-zsh
Date: Sun, 15 Aug 2004 23:30:33 -0400 [thread overview]
Message-ID: <A1C9823E-EF34-11D8-83BE-000502631FBD@louisville.edu> (raw)
In-Reply-To: <87n00v4we5.fsf@ceramic.fifi.org>
On Sunday, August 15, 2004, at 11:03 PM, Philippe Troin wrote:
> Aaron Davies <agdavi01@louisville.edu> writes:
>
>> How do I do return-value error handling in the middle of a pipeline?
>> I'd ideally like to keep this to as basic a shell level as possible,
>> plain (Bourne) sh-compatible if it can be done, though a bash or zsh
>> solution will be fine if not. I'm tring to write a simple script that
>> will apply a command to all processes matching a name--sort of a
>> generalized "killall". At the moment, it looks like this:
>>
>> #!/bin/sh
>>
>> name=$1
>> shift
>>
>> ps aux | grep $name | grep -v grep | grep -v $0 | awk '{ print $2 }' |
>> xargs $@
>>
>> and it works fine, and I'd like to keep it at that level of
>> simplicity. The only thing is, I'd like to make it stop and return 1
>> if there are no matching processes. (At the moment, it calls the
>> command with an empty argument list.) The intuitive thing to do seems
>> to be
>>
>> ps aux | grep $name | grep -v grep | ( grep -v $0 || exit 1 ) | awk '{
>> print $2 }' | xargs $@
>
> Use your first idiom and check $pipestatus[4].
Thanks, that seems to solve it (though it's [3], not [4]). I've
combined that with xargs's "-r" option, which aborts if there are no
arguments passed, to produce the following as the final script:
#!/bin/sh
name=$1
shift
ps aux | grep $name | grep -v grep | grep -v $0 | awk '{ print $2 }' |
xargs -r "$@"
test ${PIPESTATUS[3]} -eq 0 && exit || exit 1
--
__ __
/ ) / )
/--/ __. .__ ______ / / __. , __o _ _
/ (_(_/|_/ (_(_) / (_ (__/_(_/|_\/ <__</_/_)_
next prev parent reply other threads:[~2004-08-16 3:33 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-08-16 1:04 Aaron Davies
2004-08-16 2:42 ` Bart Schaefer
2004-08-16 3:33 ` Aaron Davies
2004-08-16 7:41 ` Bart Schaefer
2004-08-16 12:40 ` Aaron Davies
2004-08-16 14:53 ` DervishD
2004-08-17 3:06 ` Bart Schaefer
2004-08-16 3:03 ` Philippe Troin
2004-08-16 3:30 ` Aaron Davies [this message]
2004-08-16 7:51 ` Bart Schaefer
2004-08-16 12:41 ` Aaron Davies
2004-08-16 16:08 ` Dan Nelson
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