GPT on Question 14, Sep 16

I'm writing a bash script to purge orphaned children after the parent dies. What's the idiomatic way?

In Bash, trap termination and explicitly clean up the children you started:

#!/usr/bin/env bash

children=()

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

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

    exit "$rc"
}

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

worker1 &
children+=("$!")

worker2 &
children+=("$!")

wait

This handles normal exit and catchable signals. It does not handle the parent being killed with SIGKILL, crashing before cleanup, or grandchildren that detach.

For a whole process tree, the more robust idiom is to run the script in its own process group/session and terminate that group, or preferably use a supervisor such as systemd with a cgroup:

systemd-run --user --scope ./script.sh

On Linux, if each child must die immediately when its parent disappears—even after SIGKILL—have the child set:

prctl(PR_SET_PDEATHSIG, SIGTERM);

via a small wrapper before exec. Check the parent PID again after prctl to avoid the parent-death race.

Avoid blindly using trap 'kill 0' EXIT: it signals the shell’s entire process group and may kill the invoking shell or unrelated processes unless you deliberately created a separate process group.

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In Bash, trap termination and explicitly clean up the children you started:
```bash
#!/usr/bin/env bash
children=()
cleanup() {
    rc=$?
    trap - EXIT INT TERM
    if ((${#children[@]})); then
        kill -TERM "${children[@]}" 2>/dev/null || :
        wait "${children[@]}" 2>/dev/null || :
    fi
    exit "$rc"
}
trap cleanup EXIT
trap 'exit 130' INT
trap 'exit 143' TERM
worker1 &
children+=("$!")
worker2 &
children+=("$!")
wait
```
This handles normal exit and catchable signals. It does **not** handle the parent being killed with `SIGKILL`, crashing before cleanup, or grandchildren that detach.
For a whole process tree, the more robust idiom is to run the script in its own process group/session and terminate that group, or preferably use a supervisor such as systemd with a cgroup:
```bash
systemd-run --user --scope ./script.sh
```
On Linux, if each child must die immediately when its parent disappears—even after `SIGKILL`—have the child set:
```c
prctl(PR_SET_PDEATHSIG, SIGTERM);
```
via a small wrapper before `exec`. Check the parent PID again after `prctl` to avoid the parent-death race.
Avoid blindly using `trap 'kill 0' EXIT`: it signals the shell’s entire process group and may kill the invoking shell or unrelated processes unless you deliberately created a separate process group.

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