Re: How to capture pid of (system process?

[Maxime Devos <maximedevos@telenet.be>]

Jacob Hrbek schreef op ma 13-12-2021 om 21:01 [+0000]:
> I wrote this potato-make <https://github.com/spk121/potato-make> 
> definition (was simplified):
> 
> #:SRC_BEGIN sheme-mode
> #!/usr/bin/env sh
> exec guile -s "$0" "$@"
> !#
> 
> (use-modules (ice-9 futures)
>   (potato make))
> (initialize)
> 
> (: "watch" '()
>     (~ (do ((i 1 (1+ i)))
>        ((> i 6))
>      (future (system
>       "emacs"))
>      ;;(let ((emacs_pid (getpid)))
>       ;; (kill emacs_pid SIGTERM)))))
> 
> (execute)
> #:SRC_END
> 
> expecting to capture emacs's pid and kill it, but the issue is that 
> using `getpid` gets me the PID of potato-make and `getppid` of the
> shell 
> -> How can i capture just the emacs's pid?

'system' executes the command and waits for it to complete.
After it completed, the process is dead so the pid it used to have is
useless.

If you want to do things asynchronuously, you can look at open-pipe.
It should also be possible to build anything you want with the lower-
level fork, execl, dup->fdes, ... primitives (assuming things are
single-threaded).

Greetings,
Maxime