GPT on Question 14, Sep 12

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

A dead Bash process cannot clean up its children. The idiomatic solution depends on how reliably you need this to work.

Normal exits and catchable signals

Track child PIDs and clean them up with an EXIT trap:

#!/usr/bin/env bash

children=()

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

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

    exit "$status"
}

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

worker1 & children+=("$!")
worker2 & children+=("$!")

wait

This handles normal exit, errors, and HUP/INT/TERM. It does not handle SIGKILL, a kernel crash, or descendants spawned by those children.

Avoid blindly using:

trap 'kill 0' EXIT

It signals the entire current process group and may kill the invoking shell or unrelated processes unless the script is deliberately running in its own session/process group.

Reliable whole-tree cleanup

For production use, run the script under a supervisor that owns a cgroup, such as systemd:

[Service]
ExecStart=/path/to/script
KillMode=control-group

Then stopping or losing the service kills all processes in its cgroup, including grandchildren.

On Linux, another option is a small launcher that sets prctl(PR_SET_PDEATHSIG, SIGTERM) in each child, but Bash has no built-in portable equivalent. If cleanup must also work when the parent receives SIGKILL, use systemd/cgroups or another external supervisor.

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A dead Bash process cannot clean up its children. The idiomatic solution depends on how reliably you need this to work.
### Normal exits and catchable signals
Track child PIDs and clean them up with an `EXIT` trap:
```bash
#!/usr/bin/env bash
children=()
cleanup() {
    status=$?
    trap - EXIT INT TERM HUP
    if ((${#children[@]})); then
        kill -TERM "${children[@]}" 2>/dev/null || :
        wait "${children[@]}" 2>/dev/null || :
    fi
    exit "$status"
}
trap cleanup EXIT
trap 'exit 129' HUP
trap 'exit 130' INT
trap 'exit 143' TERM
worker1 & children+=("$!")
worker2 & children+=("$!")
wait
```
This handles normal exit, errors, and `HUP`/`INT`/`TERM`. It does **not** handle `SIGKILL`, a kernel crash, or descendants spawned by those children.
Avoid blindly using:
```bash
trap 'kill 0' EXIT
```
It signals the entire current process group and may kill the invoking shell or unrelated processes unless the script is deliberately running in its own session/process group.
### Reliable whole-tree cleanup
For production use, run the script under a supervisor that owns a cgroup, such as systemd:
```ini
[Service]
ExecStart=/path/to/script
KillMode=control-group
```
Then stopping or losing the service kills all processes in its cgroup, including grandchildren.
On Linux, another option is a small launcher that sets `prctl(PR_SET_PDEATHSIG, SIGTERM)` in each child, but Bash has no built-in portable equivalent. If cleanup must also work when the parent receives `SIGKILL`, use systemd/cgroups or another external supervisor.

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