GPT on Question 14, Sep 10

For children started by the Bash script, the usual pattern is to record their PIDs and clean them up with an EXIT trap:

#!/usr/bin/env bash

children=()

cleanup() {
    rc=$?
    trap - EXIT INT TERM

    if ((${#children[@]})); then
        kill -TERM -- "${children[@]}" 2>/dev/null || true
        wait "${children[@]}" 2>/dev/null || true
    fi

    exit "$rc"
}

trap cleanup EXIT
trap 'exit 130' INT
trap 'exit 143' TERM

some_command &
children+=("$!")

another_command &
children+=("$!")

wait

Important limitations:

• •EXIT traps do not run if the parent receives SIGKILL, crashes severely, or the machine loses power.
• •This only handles recorded direct children, not necessarily grandchildren or processes that daemonize.
• •Avoid blindly using kill 0 or kill -- -$$; those signal an entire process group and may include unrelated processes or the shell itself.

If children must die even when the Bash parent is killed with SIGKILL, use an external mechanism:

• •systemd service/cgroup with KillMode=control-group—generally the most robust option.
• •On Linux, have each child set prctl(PR_SET_PDEATHSIG, SIGTERM).
• •Run the workload in a dedicated process group/session managed by a surviving supervisor.

So: use an EXIT trap for normal script cleanup; use a supervisor/cgroup or parent-death signal for a hard guarantee.