On Friday 04 May 2012 15:02:27 John Kearney wrote:
> Am 04.05.2012 20:53, schrieb Mike Frysinger:
> > On Friday 04 May 2012 13:46:32 Andreas Schwab wrote:
> >> Mike Frysinger <vap...@gentoo.org> writes:
> >>> i wish there was a way to use `wait` that didn't block until all the
> >>> pids returned. maybe a dedicated option, or a shopt to enable this,
> >>> or a new command.
> >>>
> >>> for example, if i launched 10 jobs in the background, i usually want to
> >>> wait for the first one to exit so i can queue up another one, not wait
> >>> for all of them.
> >>
> >> If you set -m you can trap on SIGCHLD while waiting.
> >
> > awesome, that's a good mitigation
> >
> > #!/bin/bash
> > set -m
> > cnt=0
> > trap ': $(( --cnt ))' SIGCHLD
> > for n in {0..20} ; do
> >
> > (
> >
> > d=$(( RANDOM % 10 ))
> > echo $n sleeping $d
> > sleep $d
> >
> > ) &
> >
> > : $(( ++cnt ))
> >
> > if [[ ${cnt} -ge 10 ]] ; then
> >
> > echo going to wait
> > wait
> >
> > fi
> >
> > done
> > trap - SIGCHLD
> > wait
> >
> > it might be a little racy (wrt checking cnt >= 10 and then doing a wait),
> > but this is good enough for some things. it does lose visibility into
> > which pids are live vs reaped, and their exit status, but i more often
> > don't care about that ...
>
> That won't work I don't think.seemed to work fine for me > I think you meant something more like this? no. i want to sleep the parent indefinitely and fork a child asap (hence the `wait`), not busy wait with a one second delay. the `set -m` + SIGCHLD interrupted the `wait` and allowed it to return. -mike
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