Make process-running-child-p return foreground process group ID

* etc/NEWS: Mention change to `process-running-child-p`.

* src/process.c (Fprocess_running_child_p): Return number identifier of
the foreground process group if we know it.

2 files changed, 11 insertions, 3 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 99b7ec731fe..815c117308b 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,8 @@
+2015-03-24  Daniel Colascione  <dancol@dancol.org>
+
+        * process.c (Fprocess_running_child_p): Return number identifier of
+        the foreground process group if we know it.
+
 2015-03-23  Paul Eggert  <eggert@cs.ucla.edu>
 
         Minor refactoring of new Fmake_process code
diff --git a/src/process.c b/src/process.c
index dd61f3008de..3fe8644b48a 100644
--- a/src/process.c
+++ b/src/process.c
@@ -5739,9 +5739,10 @@ emacs_get_tty_pgrp (struct Lisp_Process *p)
 
 DEFUN ("process-running-child-p", Fprocess_running_child_p,
        Sprocess_running_child_p, 0, 1, 0,
-       doc: /* Return t if PROCESS has given the terminal to a child.
-If the operating system does not make it possible to find out,
-return t unconditionally.  */)
+       doc: /* Return non-nil if PROCESS has given the terminal to a
+child.  If the operating system does not make it possible to find out,
+return t.  If we can find out, return the numeric ID of the foreground
+process group.  */)
   (Lisp_Object process)
 {
   /* Initialize in case ioctl doesn't exist or gives an error,
@@ -5764,6 +5765,8 @@ return t unconditionally.  */)
 
   if (gid == p->pid)
     return Qnil;
+  if (gid != -1)
+    return make_number (gid);
   return Qt;
 }