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 ...
-mike
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