diff -r 9d1fb6a9104b Doc/library/os.rst
--- a/Doc/library/os.rst	Thu May 19 19:56:12 2011 +0200
+++ b/Doc/library/os.rst	Thu May 19 22:21:09 2011 +0200
@@ -1298,6 +1298,7 @@
           O_NOCTTY
           O_SHLOCK
           O_EXLOCK
+          O_CLOEXEC
 
    These constants are only available on Unix.
 
diff -r 9d1fb6a9104b Lib/test/test_posix.py
--- a/Lib/test/test_posix.py	Thu May 19 19:56:12 2011 +0200
+++ b/Lib/test/test_posix.py	Thu May 19 22:21:09 2011 +0200
@@ -9,6 +9,7 @@
 import sys
 import time
 import os
+import fcntl
 import pwd
 import shutil
 import stat
@@ -307,6 +308,12 @@
                 fp1.close()
                 fp2.close()
 
+    @unittest.skipUnless(hasattr(os, 'O_CLOEXEC'), "needs os.O_CLOEXEC")
+    def test_oscloexec(self):
+        fd = os.open(support.TESTFN, os.O_RDONLY|os.O_CLOEXEC)
+        self.addCleanup(os.close, fd)
+        self.assertTrue(fcntl.fcntl(fd, fcntl.F_GETFD) & fcntl.FD_CLOEXEC)
+
     def test_osexlock(self):
         if hasattr(posix, "O_EXLOCK"):
             fd = os.open(support.TESTFN,
diff -r 9d1fb6a9104b Modules/posixmodule.c
--- a/Modules/posixmodule.c	Thu May 19 19:56:12 2011 +0200
+++ b/Modules/posixmodule.c	Thu May 19 22:21:09 2011 +0200
@@ -9783,6 +9783,9 @@
 #ifdef PRIO_USER
     if (ins(d, "PRIO_USER", (long)PRIO_USER)) return -1;
 #endif
+#ifdef O_CLOEXEC
+    if (ins(d, "O_CLOEXEC", (long)O_CLOEXEC)) return -1;
+#endif
 /* posix - constants for *at functions */
 #ifdef AT_SYMLINK_NOFOLLOW
         if (ins(d, "AT_SYMLINK_NOFOLLOW", (long)AT_SYMLINK_NOFOLLOW)) return -1;