waitpid

Wait for arbitrary (non-child) processes to exit.

Uses pidfd_open(2) and poll(2) to monitor processes without requiring a parent-child relationship.

Implemented

• Wait for one or more PIDs to exit
• -v / --verbose: report when each PID exits
• -t / --timeout: maximum wait time in seconds (exit code 3 on timeout)
• -e / --exited: silently ignore already-exited PIDs
• -c / --count: exit after N processes have exited (default: all)

Exit codes

• 0: all (or --count) processes exited
• 1: general failure
• 2: system doesn’t support pidfd (ENOSYS)
• 3: timeout expired