New module 'login_tty'.

[gnulib.git] / lib / login_tty.c

diff --git a/lib/login_tty.c b/lib/login_tty.c
new file mode 100644 (file)
index 0000000..0403391
--- /dev/null
+++ b/lib/login_tty.c
@@ -0,0 +1,66 @@
+/* Assign a given terminal as controlling terminal and as standard input,
+   standard output, standard error of the current process.
+   Copyright (C) 2010 Free Software Foundation, Inc.
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include <config.h>
+
+/* Currently no specification header.  */
+
+#include <fcntl.h>
+#include <unistd.h>
+
+int
+login_tty (int slave_fd)
+{
+  int i;
+
+  /* Create a new session.  */
+  setsid ();
+
+  /* Make fd the controlling terminal for the current process.
+     On Solaris: A terminal becomes the controlling terminal of a session
+     if it is being open()ed, at a moment when
+       1. it is not already the controlling terminal of some session, and
+       2. the process that open()s it is a session leader that does not have
+          a controlling terminal.
+     We assume condition 1, try to ensure condition 2, and then open() it.  */
+  for (i = 0; i < 3; i++)
+    if (i != slave_fd)
+      close (i);
+  {
+    char *slave_name;
+    int dummy_fd;
+
+    slave_name = ttyname (slave_fd);
+    if (slave_name == NULL)
+      return -1;
+    dummy_fd = open (slave_name, O_RDWR);
+    if (dummy_fd < 0)
+      return -1;
+    close (dummy_fd);
+  }
+
+  /* Assign fd to the standard input, standard output, and standardd error of
+     the current process.  */
+  for (i = 0; i < 3; i++)
+    if (slave_fd != i)
+      if (dup2 (slave_fd, i) < 0)
+        return -1;
+  if (slave_fd >= 3)
+    close (slave_fd);
+
+  return 0;
+}