Executing Multiple Subprocesses in Parallel

parallel.sh

#!/usr/bin/env bash

# kill all subprocesses when the user presses CTRL + C
trap "kill 0" SIGINT

# exit on first failed command (good practice)
set -e

echo "Starting"

# The ampersand will execute the given shell as a subprocess.
( echo "Starting 3"; sleep 3; echo "waited for 3") &
( echo "Starting 2"; sleep 2; echo "waited for 2") &
( echo "Starting 1"; sleep 1; echo "waited for 1") &

# Waits for all subshells to complete
wait

echo "Done"

# Output:
# Starting
# Starting 3
# Starting 2
# Starting 1
# waited for 1
# waited for 2
# waited for 3
# Done