Revised exit status writing. The child uses system instead of exec and writes $? to its own pidfile; the parent writes $? to the pidfile if it is non-zero. This allows either the parent or child to get zapped by a signal, leave the other running and correctly record the status. It also means that the pidfiles may be 4 lines long on failure. Fix there is to read [0..2] to check the status on the way in for restarts.