reap

Watch a process and kill child processes when it dies.

On macOS, when a parent process exits, its child processes are reparented to launchd and keep running. reap solves this by monitoring a specified process via kqueue and terminating the child process group when it exits.

Usage

reap [--watch <pid>] -- <command> [args...]

By default, reap watches its own parent process. Use --watch <pid> to watch an arbitrary process.

Example: sketchybar

In sketchybar's config script (sketchybarrc), background processes outlive sketchybar because the shell script exits immediately. Use $PPID (which is sketchybar's PID from the script's perspective) to watch sketchybar:

reap --watch $PPID -- ./plugin.sh &

When sketchybar exits, reap kills plugin.sh and its descendants.

How it works

1. Spawns the child command in a new process group
2. Monitors the watched PID using kqueue EVFILT_PROC + NOTE_EXIT (zero polling overhead)
3. Forwards SIGTERM/SIGINT to the child process group
4. When the watched process exits: sends SIGTERM to the child group, waits up to 5 seconds, then escalates to SIGKILL
5. Propagates the child's exit code (or 128 + signal if killed by a signal)

Installation

cargo install reap-process

Building from source

git clone https://github.com/typester/reap.git
cd reap
cargo build --release

Requirements

• macOS (uses kqueue, which has no Linux equivalent for this purpose)

License

MIT