* emacs --daemon should provide a way to get its process id
@ 2008-10-31 19:19 Ulrich Mueller
2008-11-01 14:05 ` bwoster
2008-11-02 1:55 ` Stefan Monnier
0 siblings, 2 replies; 5+ messages in thread
From: Ulrich Mueller @ 2008-10-31 19:19 UTC (permalink / raw
To: emacs-devel
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Hi,
I've played around with "emacs --daemon" and different ways of
starting/stopping it, as a user and also as a system service (managed
by OpenRC's "start-stop-daemon"). What seems to be missing is an easy
way to get the process id of the daemon.
Most other programs running as a daemon save their process id in a
file, typically located under /var/run.
While I believe that "emacs --daemon" shouldn't do this by default,
an option to enable it would be very useful.
Any opinions about attached patch which adds a "--pidfile" option?
Ulrich
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2008-10-31 Ulrich Mueller <ulm@kph.uni-mainz.de>
* emacs.c (pid_file): New variable.
(main): Save process id of child in file pid_file.
(shut_down_emacs): Unlink pid_file.
(standard_args, USAGE1): Add --pidfile.
--- emacs-orig/src/emacs.c 29 Oct 2008 18:03:03 -0000 1.454
+++ emacs/src/emacs.c 31 Oct 2008 17:08:19 -0000
@@ -242,6 +242,9 @@
startup. */
int daemon_pipe[2];
+/* Name of the file where the daemon's process id is saved. */
+static char *pid_file;
+
/* Save argv and argc. */
char **initial_argv;
int initial_argc;
@@ -274,6 +277,7 @@
--no-site-file do not load site-start.el\n\
--no-splash do not display a splash screen on startup\n\
--no-window-system, -nw do not communicate with X, ignoring $DISPLAY\n\
+--pidfile FILE save process id in FILE; only with --daemon\n\
--quick, -Q equivalent to -q --no-site-file --no-splash\n\
--script FILE run FILE as an Emacs Lisp script\n\
--terminal, -t DEVICE use DEVICE for terminal I/O\n\
@@ -1080,6 +1084,7 @@
{
#ifndef DOS_NT
pid_t f;
+ char *pfile_arg = NULL;
/* Start as a daemon: fork a new child process which will run the
rest of the initialization code, then exit.
@@ -1146,6 +1151,20 @@
#ifdef HAVE_SETSID
setsid();
#endif
+ if (argmatch (argv, argc, "-pidfile", "--pidfile", 5,
+ &pfile_arg, &skip_args))
+ {
+ FILE *fp;
+ pid_file = xstrdup (pfile_arg);
+ if (!(fp = fopen (pid_file, "w")))
+ {
+ fprintf (stderr, "Cannot create pid file %s: %s\n",
+ pid_file, strerror (errno));
+ exit (1);
+ }
+ fprintf (fp, "%ld\n", (long) getpid ());
+ fclose (fp);
+ }
#else /* DOS_NT */
fprintf (stderr, "This platform does not support the -daemon flag.\n");
exit (1);
@@ -1804,6 +1823,7 @@
{ "-batch", "--batch", 100, 0 },
{ "-script", "--script", 100, 1 },
{ "-daemon", "--daemon", 99, 0 },
+ { "-pidfile", "--pidfile", 98, 1 },
{ "-help", "--help", 90, 0 },
{ "-no-unibyte", "--no-unibyte", 83, 0 },
{ "-multibyte", "--multibyte", 82, 0 },
@@ -2155,6 +2175,11 @@
#endif /* HAVE_X_WINDOWS */
#endif
+#ifndef DOS_NT
+ if (pid_file)
+ unlink (pid_file);
+#endif
+
#ifdef SIGIO
/* There is a tendency for a SIGIO signal to arrive within exit,
and cause a SIGHUP because the input descriptor is already closed. */
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: emacs --daemon should provide a way to get its process id
2008-10-31 19:19 emacs --daemon should provide a way to get its process id Ulrich Mueller
@ 2008-11-01 14:05 ` bwoster
2008-11-01 17:33 ` Ulrich Mueller
2008-11-02 1:55 ` Stefan Monnier
1 sibling, 1 reply; 5+ messages in thread
From: bwoster @ 2008-11-01 14:05 UTC (permalink / raw
To: Emacs-devel
Ulrich Mueller-2 wrote:
>
> by OpenRC's "start-stop-daemon"). What seems to be missing is an easy
> way to get the process id of the daemon.
> Most other programs running as a daemon save their process id in a
> file, typically located under /var/run.
> ...
> Any opinions about attached patch which adds a "--pidfile" option?
> ...
> Ulrich
>
I'm all for it! I've just spent an hour trying to test out an init.d script,
but it is not very robust without a pidfile, so your patch would make things
so much easier...
Emacs does have the (emacs-pid) lisp function, but that too is not easy to
try, and there may be race conditions when two --daemons are started.
Actually... with your patch, if two emacs --daemon --pidfile=same_file are
started, what will happen?
--
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^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: emacs --daemon should provide a way to get its process id
2008-11-01 14:05 ` bwoster
@ 2008-11-01 17:33 ` Ulrich Mueller
0 siblings, 0 replies; 5+ messages in thread
From: Ulrich Mueller @ 2008-11-01 17:33 UTC (permalink / raw
To: bwoster; +Cc: emacs-devel
>>>>> On Sat, 1 Nov 2008, bwoster wrote:
>> Any opinions about attached patch which adds a "--pidfile" option?
> I'm all for it! I've just spent an hour trying to test out an init.d
> script, but it is not very robust without a pidfile, so your patch
> would make things so much easier...
> Emacs does have the (emacs-pid) lisp function, but that too is not
> easy to try, and there may be race conditions when two --daemons are
> started.
> Actually... with your patch, if two emacs --daemon
> --pidfile=same_file are started, what will happen?
The second one will win and overwrite the file. That's why you
normally start daemons with a tool like "start-stop-daemon" which
takes care of locking.
Ulrich
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: emacs --daemon should provide a way to get its process id
2008-10-31 19:19 emacs --daemon should provide a way to get its process id Ulrich Mueller
2008-11-01 14:05 ` bwoster
@ 2008-11-02 1:55 ` Stefan Monnier
2008-11-02 2:18 ` Juanma Barranquero
1 sibling, 1 reply; 5+ messages in thread
From: Stefan Monnier @ 2008-11-02 1:55 UTC (permalink / raw
To: Ulrich Mueller; +Cc: emacs-devel
> I've played around with "emacs --daemon" and different ways of
> starting/stopping it, as a user and also as a system service (managed
> by OpenRC's "start-stop-daemon"). What seems to be missing is an easy
> way to get the process id of the daemon.
You can use the --eval argument to make the daemon write its (emacs-pid)
to some file. I think that'll be enough for now.
Stefan
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: emacs --daemon should provide a way to get its process id
2008-11-02 1:55 ` Stefan Monnier
@ 2008-11-02 2:18 ` Juanma Barranquero
0 siblings, 0 replies; 5+ messages in thread
From: Juanma Barranquero @ 2008-11-02 2:18 UTC (permalink / raw
To: Stefan Monnier; +Cc: Ulrich Mueller, emacs-devel
On Sun, Nov 2, 2008 at 02:55, Stefan Monnier <monnier@iro.umontreal.ca> wrote:
> You can use the --eval argument to make the daemon write its (emacs-pid)
> to some file. I think that'll be enough for now.
Also, if server.el is configured to use TCP, the emacs pid is written
to the server authentication file.
Juanma
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2008-11-02 2:18 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz follow: Atom feed
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2008-10-31 19:19 emacs --daemon should provide a way to get its process id Ulrich Mueller
2008-11-01 14:05 ` bwoster
2008-11-01 17:33 ` Ulrich Mueller
2008-11-02 1:55 ` Stefan Monnier
2008-11-02 2:18 ` Juanma Barranquero
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