A simple way of checking the exit code of commands which have been run concurrently.

monitor-concurrent-commands.sh

sleep_times=('4' '1' '2' '5' '0')
pids=()

for sleep_time in ${sleep_times[@]}
do
    sleep $sleep_time &
    pids=(${pids[@]} $!)
done

for pid in ${pids[@]}
do
    wait $pid
    echo "$pid returned $?"
done

exit

sample-output.txt

6287 returned 0
6288 returned 0
6289 returned 0
6290 returned 0
6291 returned 0
0.00s user 0.01s system 0% cpu 5.008 total

Did you look at GNU Parallel?

Also, this example reminds me of sleep sort which is on 4chan of all places...