Kill and wait for children in shell scripts

supervisor.sh

#!/bin/bash

trap 'kill 0; wait' EXIT

./zombie.sh 5 &
./zombie.sh 10 &
./zombie.sh 5

test.sh

#!/bin/bash

./supervisor.sh &
SUPERVISOR_PID=$!

wait_for_children() {
  echo "Zombies running:"
  ps aux | grep zombie

  echo "Waiting for supervisor to exit."
  wait $SUPERVISOR_PID

  echo "Zombies running:"
  ps aux | grep zombie

  EPOCH=$(date +%s)
  WAIT_SECONDS=$(( $EPOCH - $KILL_EPOCH ))
  echo "Waited $WAIT_SECONDS seconds"
}

trap wait_for_children EXIT

sleep 1
echo "Zombies running:"
ps aux | grep zombie

sleep 1
KILL_EPOCH=$(date +%s)
echo "Killing supervisor."
kill $SUPERVISOR_PID

# Catch signal from supervisor
sleep 60

zombie.sh

#!/bin/bash

DELAY=$1
trap "exec -a zombie_delayer sleep $DELAY" EXIT

(exec -a zombie_sleeper sleep 60)