ludic/docs/language/process/process-poll.md

id	name	category	kind	tokens	sig	tip	order	ns	member
process-poll	Process.poll	process	namespace-method	Process.poll	Process.poll(handle) -> int	-1 while running, else the exit code.	1	Process	poll

Returns -1 while the child is still running and its exit code once it has ended; it never waits. The code is kept, so asking again gives the same answer until Process.free.

A child ended by a signal (macOS) answers 128 plus the signal number, as a shell reports it — 137 after Process.kill, on both platforms. On Windows the code is the child's DWORD exit code as an int, so a crash such as 0xC0000005 arrives as a negative number (test for != 0, not > 0); a code of 0xFFFFFFFF is reported as 255 so that -1 always means "still running". A handle that is not one answers 255.

program Demo {
  state DemoState {
    game: int = -1
  }
  handler Watch(demo_st: mut DemoState) phase Update {
    if demo_st.game >= 0 {
      let code = Process.poll(handle: demo_st.game)
      if code >= 0 or code < -1 {
        if code != 0 { print("the game crashed") }
        Process.free(handle: demo_st.game)
        demo_st.game = -1
      }
    }
  }
}