[PATCH 4/5] Allow the systed socket fd to be retrieved.

[Matthew Leach]

* src/emacs.c (Fsystemd_socket_fd): New.
---
 src/emacs.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/src/emacs.c b/src/emacs.c
index 5a87bcd..da869af 100644
--- a/src/emacs.c
+++ b/src/emacs.c
@@ -2368,6 +2368,18 @@ When systemd passes a socket through to emacs, return 
`t'.*/)
 #endif
 }
 
+DEFUN ("systemd-socket-fd", Fsystemd_socket_fd, Ssystemd_socket_fd, 0, 0, 0,
+       doc: /* Returns the fd of the socket that systemd will pass through.
+When systemd support is not enabled, return nil.*/)
+  (void)
+{
+#ifdef HAVE_SYSTEMD
+    return make_number (SD_LISTEN_FDS_START);
+#else
+    return Qnil;
+#endif
+}
+
 DEFUN ("daemon-initialized", Fdaemon_initialized, Sdaemon_initialized, 0, 0, 0,
        doc: /* Mark the Emacs daemon as being initialized.
 This finishes the daemonization process by doing the other half of detaching
@@ -2437,6 +2449,7 @@ syms_of_emacs (void)
   defsubr (&Sinvocation_directory);
   defsubr (&Sdaemonp);
   defsubr (&Ssystemd_socket);
+  defsubr (&Ssystemd_socket_fd);
   defsubr (&Sdaemon_initialized);
 
   DEFVAR_LISP ("command-line-args", Vcommand_line_args,
-- 
2.7.4