Killing a backgrounded bash subshell leaves the running child script orphaned: kill the child PID too

If you start a sequence as ( ./a.sh; ./b.sh ) & and later kill the subshell's PID to restart it, the subshell dies but the child currently running (a.sh) is reparented to launchd/init and keeps going. You end up with two copies racing (e.g. two waiters both about to start a benchmark).

Fix: - Check with ps -ax -o pid,ppid,command | grep '[a].sh' after the kill. A PPID of 1 means an orphan. Kill it by its PID, not by pattern, on shared machines. - Better: start the sequence with set -m or setsid so it gets its own process group, then kill -- -PGID. - Or put trap 'kill 0' TERM in the wrapper so the children die with it.