Manual Pages  — PWAIT

Start two sleep(1) processes in the background. The first one will sleep for 30 seconds and the second one for one hour. Wait for any of them to finish but no more than 5 seconds. Since a timeout occurs the exit status is 124:

$ sleep 30 & sleep 3600 &
[1] 1646
[2] 1647
$ pwait -o -t5 1646 1647
$?
124

Same as above but try to obtain the exit status of the processes. In this case ‘timeout’ is shown and the exit status is 124:

$ sleep 30 & sleep 3600 &
[1] 1652
[2] 1653
$ pwait -v -t 5 1652 1653
timeout
$?
124

Start two sleep(1) processes in the background sleeping for 30 and 40 seconds respectively. Wait 60 seconds for any of them to finish and get their exit codes:

$ sleep 30 & sleep 40 &
[1] 1674
[2] 1675
$ pwait -v -t 60 1674 1675
1674: exited with status 0.
1675: exited with status 0.
[1]-  Done                    sleep 30
[2]+  Done                    sleep 40
$ echo $?
0

kill(1), pkill(1), ps(1), wait(1), kqueue(2)

pwait is not a substitute for the wait(1) builtin as it will not clean up any zombies or state in the parent process.

To avoid deadlock, pwait will ignore its own pid, if it is provided as a process id to wait for.