job control about racket-rash HOT 4 OPEN

My plan at this point is to have unix-style job control for pipelines consisting only of subprocess, and punt job control for other things to a future time.

Job control involving Racket code really wants to be thread-based, and would just use threads except that various bits of state are thread-local. For example, cd changes the current-directory parameter, but if it's run in a different thread then it won't change anything outside of that thread since parameters are thread-local. If there were a way to get the state out of a completed thread, I think that is how I would want to do job control for Racket commands -- run in a thread, and then when the foreground thread finishes update the REPL thread with the state from the done foreground thread.

from racket-rash.

Another new embedded lisp shell Janetsh has job control working, so perhaps I should see what series of syscalls it's using and how it differs from my job-control branch. It's likely to have cleaner code there than Bash and Zsh, which I was looking at when I was trying to implement it.

from racket-rash.

I made some progress on this today. One major problem from the last time I tried it is that there is some initialization that the shell must do that I didn't know about. Now that's working. The biggest problem now is what to do about Racket using SIGCHLD, which notifies a parent when a child exits OR stops (I think). Anyway, I can wait for the subprocess to exit with Racket, but I also need to be able to wait on subprocesses stopping, eg. when they get SIGTSTP, so the shell can resume with the job backgrounded. If I can figure out how to do that, then it should be pretty easy to get my code otherwise working.

from racket-rash.

Well, I'm not so sure about using SIGCHLD, but I think waitpid is the right way to do this. But Racket uses waitpid as well, perhaps I need to figure out what it's doing and see if it conflicts with what I'm trying to do...

from racket-rash.