How do I kill background processes / jobs when my shell script exits?

Question

I am looking for a way to clean up the mess when my top-level script exits.

Especially if I want to use set -e, I wish the background process would die when the script exits.

Answer 1

To clean up some mess, trap can be used. It can provide a list of stuff executed when a specific signal arrives:

trap "echo hello" SIGINT

but can also be used to execute something if the shell exits:

trap "killall background" EXIT

It's a builtin, so help trap will give you information (works with bash). If you only want to kill background jobs, you can do

trap 'kill $(jobs -p)' EXIT

Watch out to use single ', to prevent the shell from substituting the $() immediately.