I want to run a couple Bash processes in parallel in the background. If I use "wait", I might end up waiting for a long-running process to finish after another process has already failed, and in this case I want to stop as soon as I see the failure.

bash_waiter.sh

#!/bin/bash

wait_all() {
    # As soon as one of the background processes creates the EPIC_FAIL file,
    # kill all background processes, rm EPIC_FAIL, and stop looping.
    while [ $(jobs | grep -v Done | wc -l) -ne 0 ]; do
        sleep 1
        if [ -f EPIC_FAIL ]; then
            rm -f EPIC_FAIL
            echo OUCH
            for job in `jobs -p`; do
                kill -9 $job
            done
            break
        fi
    done
}

# If your process fails, it should 'touch EPIC_FAIL'

(sleep 2; touch EPIC_FAIL) &
# (sleep 2; echo nope) &
(sleep 5; echo NOPE) &
wait_all