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Re: [PATCH] silent job monitor when 'set +m'


From: Chet Ramey
Subject: Re: [PATCH] silent job monitor when 'set +m'
Date: Mon, 9 Nov 2009 14:22:37 -0500

> > It doesn't require a subshell to save and restore stderr.
> 
> At first I thought the same. And then I read this:
> 
> <http://bash-hackers.org/wiki/doku.php/snipplets/kill_bg_job_without_message>
> 
>   It's also useless to temporarily redirect stderr when you call the
>   kill command, since the successful termination of the job, the
>   termination of the kill command and the message from the shell may not
>   happen at the same time. And a blind sleep after the kill would be
>   just a workaround.
> 
> Doesn't some permanently redirected subshell solves this race condition?

Maybe, but I don't think it's necessary.  I haven't tested it, but
what's wrong with

redirect stderr
kill pid
wait pid
restore stderr

It seems to me that this sequence forces the necessary synchronicity.

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/




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