linux - Bash: wait with timeout

Question

In a Bash script, I would like to do something like:

app1 &
pidApp1=$!
app2 &
pidApp2=$1

timeout 60 wait $pidApp1 $pidApp2
kill -9 $pidApp1 $pidApp2

I.e., launch two applications in the background, and give them 60 seconds to complete their work. Then, if they don't finish within that interval, kill them.

Unfortunately, the above does not work, since timeout is an executable, while wait is a shell command. I tried changing it to:

timeout 60 bash -c wait $pidApp1 $pidApp2

But this still does not work, since wait can only be called on a PID launched within the same shell.

Any ideas?

Answer 1

Both your example and the accepted answer are overly complicated, why do you not only use timeout since that is exactly its use case? The timeout command even has an inbuilt option (-k) to send SIGKILL after sending the initial signal to terminate the command (SIGTERM by default) if the command is still running after sending the initial signal (see man timeout).

If the script doesn't necessarily require to wait and resume control flow after waiting it's simply a matter of

timeout -k 60s 60s app1 &
timeout -k 60s 60s app2 &
# [...]

If it does, however, that's just as easy by saving the timeout PIDs instead:

pids=()
timeout -k 60s 60s app1 &
pids+=($!)
timeout -k 60s 60s app2 &
pids+=($!)
wait "${pids[@]}"
# [...]

E.g.

$ cat t.sh
#!/bin/bash

echo "$(date +%H:%M:%S): start"
pids=()
timeout 10 bash -c 'sleep 5; echo "$(date +%H:%M:%S): job 1 terminated successfully"' &
pids+=($!)
timeout 2 bash -c 'sleep 5; echo "$(date +%H:%M:%S): job 2 terminated successfully"' &
pids+=($!)
wait "${pids[@]}"
echo "$(date +%H:%M:%S): done waiting. both jobs terminated on their own or via timeout; resuming script"

.

$ ./t.sh
08:59:42: start
08:59:47: job 1 terminated successfully
08:59:47: done waiting. both jobs terminated on their own or via timeout; resuming script