How to execute code after start-process completion?

How to execute code after start-process completion?

[Pankaj Jangid]

I am working on tiny customization of my Gnus. And using the function
`start-process` to call `notmuch new`.

#+BEGIN_SRC emacs-lisp
(add-hook 'gnus-after-getting-new-news-hook
	  (lambda ()
	    (start-process "notmuch" "*Notmuch*" "notmuch" "new")
	    ;; (print (current-time-string) (get-buffer "*Notmuch*"))
	    ))
#+END_SRC

After completion of the process (`notmuch new`), I want to execute some
code. As you can see above, I want to put the timestamp in the *Notmuch*
buffer. I know that `start-process` returns the process object. But I
couldn't find how to use it. Please share any pointers/code-snippet on
how to use that object accomplish what I want to do? Or may be there is
a different way to do the task. Please advise.

-- 
Pankaj Jangid

Re: How to execute code after start-process completion?

[Eli Zaretskii]

> From: Pankaj Jangid <pankaj@codeisgreat.org>
> Date: Sat, 26 Sep 2020 19:30:41 +0530
> 
> #+BEGIN_SRC emacs-lisp
> (add-hook 'gnus-after-getting-new-news-hook
> 	  (lambda ()
> 	    (start-process "notmuch" "*Notmuch*" "notmuch" "new")
> 	    ;; (print (current-time-string) (get-buffer "*Notmuch*"))
> 	    ))
> #+END_SRC
> 
> After completion of the process (`notmuch new`), I want to execute some
> code. As you can see above, I want to put the timestamp in the *Notmuch*
> buffer. I know that `start-process` returns the process object. But I
> couldn't find how to use it. Please share any pointers/code-snippet on
> how to use that object accomplish what I want to do? Or may be there is
> a different way to do the task. Please advise.

The usual way of doing that is to set up a process-sentinel function.
It will be called when the process finishes.

Re: How to execute code after start-process completion?

[Daniel Martín]

Pankaj Jangid <pankaj@codeisgreat.org> writes:

> I am working on tiny customization of my Gnus. And using the function
> `start-process` to call `notmuch new`.
>
> #+BEGIN_SRC emacs-lisp
> (add-hook 'gnus-after-getting-new-news-hook
> 	  (lambda ()
> 	    (start-process "notmuch" "*Notmuch*" "notmuch" "new")
> 	    ;; (print (current-time-string) (get-buffer "*Notmuch*"))
> 	    ))
> #+END_SRC
>
> After completion of the process (`notmuch new`), I want to execute some
> code. As you can see above, I want to put the timestamp in the *Notmuch*
> buffer. I know that `start-process` returns the process object. But I
> couldn't find how to use it. Please share any pointers/code-snippet on
> how to use that object accomplish what I want to do? Or may be there is
> a different way to do the task. Please advise.

You can use a process sentinel for that. Search for "process sentinel"
in the Elisp manual.

Re: How to execute code after start-process completion?

[Pankaj Jangid]

On Sat, Sep 26 2020, Eli Zaretskii wrote:

>> After completion of the process (`notmuch new`), I want to execute some
>> code. As you can see above, I want to put the timestamp in the *Notmuch*
>> buffer. I know that `start-process` returns the process object. But I
>> couldn't find how to use it. Please share any pointers/code-snippet on
>> how to use that object accomplish what I want to do? Or may be there is
>> a different way to do the task. Please advise.
>
> The usual way of doing that is to set up a process-sentinel function.
> It will be called when the process finishes.

Thanks. I am done. Here is my snippet.

#+BEGIN_SRC emacs-lisp
(defun my/timestamp-me (process event)
  "Record EVENT in the PROCESS buffer."
  (print (format "%s %s at %s" process event (current-time-string))
	 (process-buffer process)))

(defun my/notmuch-new ()
  "Execute 'notmuch new' command and logs in buffer *Notmuch*."
  (set-process-sentinel
   (start-process "notmuch" "*Notmuch*" "notmuch" "new")
   'my/timestamp-me))
#+END_SRC