shell script to spawn processes, terminate children on SIGTERM

Question

I want to write a shell script that spawns several long-running processes in the background, then hangs around. Upon receiving SIGTERM, I want all the subprocesses to terminate as well.

Basically, I want a "master process".

Here's what I got so far:

#!/bin/sh

sleep 600 &
PID1="$!"

sleep 600 &
PID2="$!"

# supposedly this should kill the child processes on SIGTERM. 
trap "kill $PID1 $PID2" SIGTERM 

wait

The above script fails with trap: 10: SIGTERM: bad trap.

Edit: I'm using Ubuntu 9.04

Answer 1

This works for me:

trap "trap - SIGTERM && kill -- -$$" SIGINT SIGTERM EXIT

• kill -- -$$ sends a SIGTERM to the whole process group, thus killing also descendants.

• Specifying signal EXIT is useful when using set -e (more details here).

Answer 2

Joe's answer put me on the right track. I also found out I should trap more signals to cover my bases.

Final script looks like this:

#!/bin/sh

sleep 600 &
PID1="$!"

sleep 600 &
PID2="$!"

trap "kill $PID1 $PID2" exit INT TERM

wait