X11 signal to emacs

X11 signal to emacs

[Perry Smith]

I'm on AIX but lets assume I'm on a "normal" platform because I'm hoping it
will be the same.

I'm using emacs (25.1) as an X11 client.

Right now, for some reason, my emacs gets stuck.  What I'd like to do is
send it a signal from a separate terminal.  I can do that but in all cases,
emacs just exits.  I've tried SIGHUP, SIGINT, and SIGTERM.

Is there a way to send a signal to emacs that emacs will catch and get out
of whatever loop it might be in at the time?  So far, I have not been able
to find a method to do that.

Thank you,
Perry

Re: X11 signal to emacs

[Dmitry Gutov]

On 23.03.2017 22:19, Perry Smith wrote:

> Right now, for some reason, my emacs gets stuck.  What I'd like to do is
> send it a signal from a separate terminal.  I can do that but in all cases,
> emacs just exits.  I've tried SIGHUP, SIGINT, and SIGTERM.

SIGUSR2 should do it. See also its mention in etc/DEBUG.

Not sure what "X11 signal" means; I send signals with 'kill': 
http://emacs.stackexchange.com/questions/506/debugging-a-frozen-emacs/649#649

Re: X11 signal to emacs

[John Mastro]

Perry Smith <pedz@easesoftware.com> wrote:
> I'm on AIX but lets assume I'm on a "normal" platform because I'm hoping it
> will be the same.
>
> I'm using emacs (25.1) as an X11 client.
>
> Right now, for some reason, my emacs gets stuck.  What I'd like to do is
> send it a signal from a separate terminal.  I can do that but in all cases,
> emacs just exits.  I've tried SIGHUP, SIGINT, and SIGTERM.
>
> Is there a way to send a signal to emacs that emacs will catch and get out
> of whatever loop it might be in at the time?  So far, I have not been able
> to find a method to do that.

Try sending SIGUSR2, which instructs Emacs to try to break out of its
current loop and into the Lisp debugger.

        John

Re: X11 signal to emacs

[Emanuel Berg]

Perry Smith wrote:

> Is there a way to send a signal to emacs that
> emacs will catch and get out of whatever loop
> it might be in at the time? So far, I have
> not been able to find a method to do that.

Evaluate these, then evaluate the commented-out
in-Emacs test or run the shell command. (If you
are a bash user syntax may vary slightly.)

(defun signal-usr1-f ()
  (interactive)
  (message "Got signal: USR1") )

(define-key special-event-map [sigusr1] #'signal-usr1-f)

;; test:
;;
;;  from emacs:  (signal-process (emacs-pid) 'sigusr1)
;;
;;   from zsh:   kill -s usr1 $(ps -e | grep emacs | cut -d " " -f 2)

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Re: X11 signal to emacs

[raman]

Emanuel Berg <moasen@zoho.com> writes:
This is nice. Is there some X magic that will let me combine
special-event-map  with something else that then lets me bind an action
to a simple press of say the ctrl-key?

Today, ctrl is a modifier --  but pressing ctrl by itself does nothing
in emacs. If I could achieve the above, then I'd get 3 more keys: ctrl,
alt, and the windows key.
> Perry Smith wrote:
>
>> Is there a way to send a signal to emacs that
>> emacs will catch and get out of whatever loop
>> it might be in at the time? So far, I have
>> not been able to find a method to do that.
>
> Evaluate these, then evaluate the commented-out
> in-Emacs test or run the shell command. (If you
> are a bash user syntax may vary slightly.)
>
> (defun signal-usr1-f ()
>   (interactive)
>   (message "Got signal: USR1") )
>
> (define-key special-event-map [sigusr1] #'signal-usr1-f)
>
> ;; test:
> ;;
> ;;  from emacs:  (signal-process (emacs-pid) 'sigusr1)
> ;;
> ;;   from zsh:   kill -s usr1 $(ps -e | grep emacs | cut -d " " -f 2)

-- 

Re: X11 signal to emacs

[Emanuel Berg]

raman wrote:

> This is nice. Is there some X magic that will
> let me combine special-event-map with
> something else that then lets me bind an
> action to a simple press of say the ctrl-key?

Hang on a second, X? Now I see, it even says
X11 in the subject. X11 is the protocol for X.
Do they have signals of their own?!

My answer has nothing to do with X or X11, it
is plain Unix IPC, just two processes
signalling each other...

> Today, ctrl is a modifier -- but pressing
> ctrl by itself does nothing in emacs.
> If I could achieve the above, then I'd get 3
> more keys: ctrl, alt, and the windows key.

Cool idea, cred if you succeed. But in general,
one doesn't need more keys. It is doing
something sensible with the ones you got that's
the trick :)

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