Proper job control in Bash scripts

README.md

Proper job control in Bash scripts

Simple example of how to properly launch background jobs and then gracefully terminate them.

Gotchas

1. We could trap only the EXIT signal, but then after killing workers we get an unwanted "Terminated" message.
2. In worker scripts, we must call exit when cleaning, to break out of the infinite loop
3. After killing a worker, we still have to wait for them to gracefully terminate.

Further reading

• Job Control Commands

main

#!/usr/bin/env bash

clean() {
	echo
	kill $(jobs -pr)
	wait
	echo 'main clean'
}

main() {
	local self="$0"
	local base="$(dirname "$self")"

	trap 'clean' 'SIGINT' 'SIGTERM'

	"$base/worker" 'A' &
	"$base/worker" 'B' &
	"$base/worker" 'C' &

	wait
}

main "$@"

worker

#!/usr/bin/env bash

clean() {
	local name="$1"

	echo "worker $name clean"
	exit 0
}

main() {
	local name="$1"

	trap "clean '$name'" 'SIGINT' 'SIGTERM'

	while true; do
		sleep "$(($RANDOM % 5 + 1))"
		echo "worker $name tick"
	done
}

main "$@"