Re: call-process blocks the active thread

[Eric Abrahamsen <eric@ericabrahamsen.net>]

Elias Mårtenson <lokedhs@gmail.com> writes:

> I was trying to use ‘call-process’ in a thread in order to not have to deal with process buffers and the like while still being able to run an external program in the
> background.
>
> As it turns out, ‘call-process’ hangs all of Emacs while the external program is run.
>
> To reproduce, simply type M-: (make-thread (lambda () (call-process "sleep" nil nil nil "2")))
>
> This will hang Emacs for 2 seconds.

`call-process' will block Emacs no matter what. Threads are good for
encapsulating environment, but they don't really change the nature of
synchronous/asynchronous external processes. You still have to do:

(let ((proc (start-process <etc>)))
  (while (process-live-p proc)
    (accept-process-output proc)))
    
caveat: I am not a thread expert

Eric