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Re: different exit codes in $? and ${PIPESTATUS[@]}
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From: |
Chet Ramey |
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Subject: |
Re: different exit codes in $? and ${PIPESTATUS[@]} |
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Date: |
Sun, 14 Oct 2012 13:10:17 -0400 |
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Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6; rv:15.0) Gecko/20120907 Thunderbird/15.0.1 |
On 10/14/12 7:26 AM, Dan Douglas wrote:
> On Sunday, October 14, 2012 11:46:17 AM Wladimir Sidorenko wrote:
>> To my mind '!' looks pretty much like a unary operator and '|' like a binary
> one.
>
> This isn't as confusing as the associativity and nesting problem.
Think of `!' and `time' as reserved words that modify a pipeline rather
than operators that begin one. You can stack `!' and `time' so that
consecutive instances modify the same pipeline rather than delimit them.
It's a little easier to see how ! ! is a no-op that way.
There was an extensive discussion of this on the Posix list back a
couple of years. Geoff Clare wrote the final version of a set of
proposed changes that made a distinction between pipelines, `unadorned'
pipelines, `negated' pipelines, `timed' pipelines, and allowed the `!'
and `time' reserved words to modify the same pipeline. I'm not sure why
a lot of that work didn't make it into the published standard, but it
was clarifying.
https://www5.opengroup.org/sophocles2/show_mail.tpl?CALLER=show_archive.tpl&source=L&listname=austin-group-l&id=12082
Chet
--
``The lyf so short, the craft so long to lerne.'' - Chaucer
``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, ITS, CWRU chet@case.edu http://cnswww.cns.cwru.edu/~chet/
- Re: different exit codes in $? and ${PIPESTATUS[@]}, (continued)
- Re: different exit codes in $? and ${PIPESTATUS[@]}, Andreas Schwab, 2012/10/10
- Re: different exit codes in $? and ${PIPESTATUS[@]}, Chet Ramey, 2012/10/12
- Re: different exit codes in $? and ${PIPESTATUS[@]}, Wladimir Sidorenko, 2012/10/12
- Re: different exit codes in $? and ${PIPESTATUS[@]}, Eric Blake, 2012/10/12
- Re: different exit codes in $? and ${PIPESTATUS[@]}, Chet Ramey, 2012/10/13
- Re: different exit codes in $? and ${PIPESTATUS[@]}, Wladimir Sidorenko, 2012/10/14
- Re: different exit codes in $? and ${PIPESTATUS[@]}, Andreas Schwab, 2012/10/14
- Re: different exit codes in $? and ${PIPESTATUS[@]}, Wladimir Sidorenko, 2012/10/14
- Re: different exit codes in $? and ${PIPESTATUS[@]}, Chet Ramey, 2012/10/14
- Re: different exit codes in $? and ${PIPESTATUS[@]}, Dan Douglas, 2012/10/14
- Re: different exit codes in $? and ${PIPESTATUS[@]},
Chet Ramey <=
- Re: different exit codes in $? and ${PIPESTATUS[@]}, Dan Douglas, 2012/10/15
- Re: different exit codes in $? and ${PIPESTATUS[@]}, Chet Ramey, 2012/10/15
- Re: different exit codes in $? and ${PIPESTATUS[@]}, Chet Ramey, 2012/10/14