On 15/06/11 04:27, Michael Dale wrote:
> For the TimedMediaHandler I was adding more fine grain control over
> background processes [1] and ran into a unix issue around getting both a
> pid and exit status for a given background shell command.
>
> Essentially with a background task I can get the pid or the exit status
> but can't seem to get both:
>
> to get the pid:
> $pid = wfShellExec("nohup nice -n 19 $cmd > /tmp/stdout.log & echo $!";
>
> put the exit status into a file:
> $pid = wfShellExec("nohup nice -n 19 $cmd > /tmp/stdout.log && echo $? >
> /tmp/exit.status";
>
> But if I try to get both either my exit status is for the "echo pid"
> command or my pid is for the "echo exit status" command. It seems like
> there should be some shell trick back-reference background tasks or
> something
Maybe something like:
#!/bin/bash
trap 'kill %1' SIGINT SIGTERM
(
$cmd > /tmp/stdout.log
echo $? > /tmp/exit.status
) &
subshell="$!"
cmdpid=
# Wait for the command to start
for i in `seq 100`;do
cmdpid=`ps --ppid "$subshell" -o pid --no-headers`
if [ -n "$cmdpid" ]; then
break
fi
sleep 0.1
done
# Return the PID to MediaWiki
echo "$cmdpid"
There comes a point with every shell script project where you realise
it would have been easier to use a real programming language from the
start. In this case, doing it in PHP with pcntl_fork(), pcntl_exec()
and pcntl_wait() would be a reasonable solution. In my experience, you
can't ask the question "how do I do X in shell script" and expect to
like the answer.
-- Tim Starling
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