* emacs.c (standard_args): Add --daemon.

(main): Disconnect from the terminal when --daemon is passed.
(is_daemon): New variable.
(Fdaemonp): New function.
(syms_of_emacs): Defsubr it.

* startup.el (command-line): Start the server when in daemon mode.

* cmdargs.texi (Initial Options): Document --daemon.

2 files changed, 48 insertions, 0 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 9e855a4898b..97f11fb55bc 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,11 @@
+2008-09-21  Dan Nicolaescu  <dann@ics.uci.edu>
+
+        * emacs.c (standard_args): Add --daemon.
+        (main): Disconnect from the terminal when --daemon is passed.
+        (is_daemon): New variable.
+        (Fdaemonp): New function.
+        (syms_of_emacs): Defsubr it.
+
 2008-09-20  Chong Yidong  <cyd@stupidchicken.com>
 
         * xdisp.c (get_next_display_element): Handle string display
diff --git a/src/emacs.c b/src/emacs.c
index 68127df0c06..131662c27a1 100644
--- a/src/emacs.c
+++ b/src/emacs.c
@@ -232,6 +232,9 @@ int noninteractive;
 
 int noninteractive1;
 
+/* Nonzero means Emacs was started as a daemon.  */
+int is_daemon = 0;
+
 /* Save argv and argc.  */
 char **initial_argv;
 int initial_argc;
@@ -1068,6 +1071,34 @@ main (int argc, char **argv)
       exit (0);
     }
 
+#ifndef DOS_NT
+  if (argmatch (argv, argc, "-daemon", "--daemon", 5, NULL, &skip_args))
+    {
+      pid_t f = fork();
+      int nfd;
+      if (f > 0)
+        exit(0);
+      if (f < 0)
+        {
+          fprintf (stderr, "Cannot fork!\n");
+          exit(1);
+        }
+
+      nfd = open("/dev/null", O_RDWR);
+      dup2(nfd, 0);
+      dup2(nfd, 1);
+      dup2(nfd, 2);
+      close (nfd);
+      is_daemon = 1;
+#ifdef HAVE_SETSID
+      setsid();
+#endif
+    }
+#else /* DOS_NT */
+  fprintf (stderr, "This platform does not support the -daemon flag.\n");
+  exit (1);
+#endif /* DOS_NT */
+
   if (! noninteractive)
     {
 #ifdef BSD_PGRPS
@@ -1719,6 +1750,7 @@ struct standard_args standard_args[] =
   { "-nw", "--no-windows", 110, 0 },
   { "-batch", "--batch", 100, 0 },
   { "-script", "--script", 100, 1 },
+  { "-daemon", "--daemon", 99, 0 },
   { "-help", "--help", 90, 0 },
   { "-no-unibyte", "--no-unibyte", 83, 0 },
   { "-multibyte", "--multibyte", 82, 0 },
@@ -2350,6 +2382,13 @@ decode_env_path (evarname, defalt)
   return Fnreverse (lpath);
 }
 
+DEFUN ("daemonp", Fdaemonp, Sdaemonp, 0, 0, 0,
+       doc: /* Make the current emacs process a daemon.*/)
+  (void)
+{
+  return is_daemon ? Qt : Qnil;
+}
+
 void
 syms_of_emacs ()
 {
@@ -2368,6 +2407,7 @@ syms_of_emacs ()
 
   defsubr (&Sinvocation_name);
   defsubr (&Sinvocation_directory);
+  defsubr (&Sdaemonp);
 
   DEFVAR_LISP ("command-line-args", &Vcommand_line_args,
                doc: /* Args passed by shell to Emacs, as a list of strings.