spawn.bash

#!/usr/bin/env bash

set -e

declare -ai pids=()

ten_seconds() {
        sleep 10s
}

twenty_seconds() {
        sleep 20s
}

for ((i=0; i < $1; i++)); do ten_seconds & pids+=($!); twenty_seconds & pids+=($!); printf "\rwaiting for %d processes to exit" "$(($i + 1))"; done

for p in "${pids[@]}"; do wait -n; printf "done: %d\n" "$p"; done