GPT on Question 14, Sep 27

In Bash, the idiom is to track child PIDs and clean them up with an EXIT trap:

#!/usr/bin/env bash

children=()

cleanup() {
    trap - EXIT
    ((${#children[@]})) || return

    kill -TERM "${children[@]}" 2>/dev/null || true
    wait "${children[@]}" 2>/dev/null || true
}

trap cleanup EXIT
trap 'exit 129' HUP
trap 'exit 130' INT
trap 'exit 143' TERM

some_command &
children+=("$!")

another_command &
children+=("$!")

wait

This handles normal exit and catchable signals. It does not handle SIGKILL, crashes, or power loss—the parent cannot run cleanup after it is already dead.

For reliable cleanup in those cases:

• •Use a supervisor/cgroup, such as a systemd service with KillMode=control-group (the default). This also catches grandchildren.
• •On Linux, have each child set prctl(PR_SET_PDEATHSIG, SIGTERM) before exec; Bash has no built-in way to do this, so a small wrapper is needed.
• •If descendants must be terminated together, place them in a dedicated process group/session and have an external supervisor kill that group.

Avoid relying on pkill -P $$: it only finds immediate children, and once they are orphaned their PPID changes. Also avoid trap 'kill 0' EXIT unless the script owns a dedicated process group, since it can kill the invoking shell too.