diff -r fee4bc043d73 Doc/library/functions.rst
--- a/Doc/library/functions.rst	Fri Jan 04 12:40:35 2013 +0200
+++ b/Doc/library/functions.rst	Fri Jan 04 15:23:33 2013 +0100
@@ -852,6 +852,7 @@ are always available.  They are listed h
    ``'w'``   open for writing, truncating the file first
    ``'x'``   open for exclusive creation, failing if the file already exists
    ``'a'``   open for writing, appending to the end of the file if it exists
+   ``'e'``   enable the close-on-exec flag
    ``'b'``   binary mode
    ``'t'``   text mode (default)
    ``'+'``   open a disk file for updating (reading and writing)
@@ -989,6 +990,9 @@ are always available.  They are listed h
       :exc:`FileExistsError` is now raised if the file opened in exclusive
       creation mode (``'x'``) already exists.
 
+   .. versionchanged:: 3.4
+      ``'e'`` mode flag was added.
+
 
 .. XXX works for bytes too, but should it?
 .. function:: ord(c)
diff -r fee4bc043d73 Lib/_pyio.py
--- a/Lib/_pyio.py	Fri Jan 04 12:40:35 2013 +0200
+++ b/Lib/_pyio.py	Fri Jan 04 15:23:33 2013 +0100
@@ -59,6 +59,7 @@ def open(file, mode="r", buffering=-1, e
     'w'       open for writing, truncating the file first
     'x'       create a new file and open it for writing
     'a'       open for writing, appending to the end of the file if it exists
+    'e'       enable the close-on-exec flag
     'b'       binary mode
     't'       text mode (default)
     '+'       open a disk file for updating (reading and writing)
@@ -163,6 +164,7 @@ def open(file, mode="r", buffering=-1, e
     if modes - set("axrwb+tU") or len(mode) > len(modes):
         raise ValueError("invalid mode: %r" % mode)
     creating = "x" in modes
+    cloexec = "e" in modes
     reading = "r" in modes
     writing = "w" in modes
     appending = "a" in modes
@@ -190,6 +192,7 @@ def open(file, mode="r", buffering=-1, e
                  (reading and "r" or "") +
                  (writing and "w" or "") +
                  (appending and "a" or "") +
+                 (cloexec and "e" or "") +
                  (updating and "+" or ""),
                  closefd, opener=opener)
     line_buffering = False
diff -r fee4bc043d73 Lib/test/test_builtin.py
--- a/Lib/test/test_builtin.py	Fri Jan 04 12:40:35 2013 +0200
+++ b/Lib/test/test_builtin.py	Fri Jan 04 15:23:33 2013 +0100
@@ -20,6 +20,10 @@ try:
     import pty, signal
 except ImportError:
     pty = signal = None
+try:
+    import fcntl
+except ImportError:
+    fcntl = None
 
 
 class Squares:
@@ -943,29 +947,24 @@ class BuiltinTest(unittest.TestCase):
     def write_testfile(self):
         # NB the first 4 lines are also used to test input, below
         fp = open(TESTFN, 'w')
-        try:
+        self.addCleanup(unlink, TESTFN)
+        with fp:
             fp.write('1+1\n')
             fp.write('The quick brown fox jumps over the lazy dog')
             fp.write('.\n')
             fp.write('Dear John\n')
             fp.write('XXX'*100)
             fp.write('YYY'*100)
-        finally:
-            fp.close()
 
     def test_open(self):
         self.write_testfile()
-        fp = open(TESTFN, 'r')
-        try:
+        with open(TESTFN, 'r') as fp:
             self.assertEqual(fp.readline(4), '1+1\n')
             self.assertEqual(fp.readline(), 'The quick brown fox jumps over the lazy dog.\n')
             self.assertEqual(fp.readline(4), 'Dear')
             self.assertEqual(fp.readline(100), ' John\n')
             self.assertEqual(fp.read(300), 'XXX'*100)
             self.assertEqual(fp.read(1000), 'YYY'*100)
-        finally:
-            fp.close()
-            unlink(TESTFN)
 
     def test_open_default_encoding(self):
         old_environ = dict(os.environ)
@@ -979,16 +978,26 @@ class BuiltinTest(unittest.TestCase):
 
             self.write_testfile()
             current_locale_encoding = locale.getpreferredencoding(False)
-            fp = open(TESTFN, 'w')
-            try:
+            with open(TESTFN, 'w') as fp:
                 self.assertEqual(fp.encoding, current_locale_encoding)
-            finally:
-                fp.close()
-                unlink(TESTFN)
         finally:
             os.environ.clear()
             os.environ.update(old_environ)
 
+    # FIXME: use subprocess to run this test on Windows
+    @unittest.skipUnless(fcntl, 'need fcntl module')
+    def test_open_cloexec(self):
+        self.write_testfile()
+        for mode in ('re', 'rbe'):
+            with open(TESTFN, mode) as fp:
+                fd = fp.fileno()
+                flags = fcntl.fcntl(fd, fcntl.F_GETFD, 0)
+                self.assertEqual(flags & fcntl.FD_CLOEXEC, flags & fcntl.FD_CLOEXEC)
+
+        def fake_opener(path, flags):
+            return 0
+        self.assertRaises(ValueError, open, TESTFN, 're', opener=fake_opener)
+
     def test_ord(self):
         self.assertEqual(ord(' '), 32)
         self.assertEqual(ord('A'), 65)
diff -r fee4bc043d73 Modules/_io/_iomodule.c
--- a/Modules/_io/_iomodule.c	Fri Jan 04 12:40:35 2013 +0200
+++ b/Modules/_io/_iomodule.c	Fri Jan 04 15:23:33 2013 +0100
@@ -123,6 +123,7 @@ PyDoc_STRVAR(open_doc,
 "'w'       open for writing, truncating the file first\n"
 "'x'       create a new file and open it for writing\n"
 "'a'       open for writing, appending to the end of the file if it exists\n"
+"'e'       enable the close-on-exec flag\n"
 "'b'       binary mode\n"
 "'t'       text mode (default)\n"
 "'+'       open a disk file for updating (reading and writing)\n"
@@ -226,7 +227,8 @@ io_open(PyObject *self, PyObject *args, 
     char *encoding = NULL, *errors = NULL, *newline = NULL;
     unsigned i;
 
-    int creating = 0, reading = 0, writing = 0, appending = 0, updating = 0;
+    int creating = 0, cloexec = 0;
+    int reading = 0, writing = 0, appending = 0, updating = 0;
     int text = 0, binary = 0, universal = 0;
 
     char rawmode[6], *m;
@@ -282,6 +284,9 @@ io_open(PyObject *self, PyObject *args, 
             universal = 1;
             reading = 1;
             break;
+        case 'e':
+            cloexec = 1;
+            break;
         default:
             goto invalid_mode;
         }
@@ -300,6 +305,7 @@ io_open(PyObject *self, PyObject *args, 
     if (reading)   *(m++) = 'r';
     if (writing)   *(m++) = 'w';
     if (appending) *(m++) = 'a';
+    if (cloexec)   *(m++) = 'e';
     if (updating)  *(m++) = '+';
     *m = '\0';
 
diff -r fee4bc043d73 Modules/_io/fileio.c
--- a/Modules/_io/fileio.c	Fri Jan 04 12:40:35 2013 +0200
+++ b/Modules/_io/fileio.c	Fri Jan 04 15:23:33 2013 +0100
@@ -221,6 +221,10 @@ fileio_init(PyObject *oself, PyObject *a
     int fd = -1;
     int closefd = 1;
     int fd_is_own = 0;
+    int cloexec = 0;
+#if defined(O_CLOEXEC) && defined(HAVE_FCNTL_H)
+    int cloexec_works = -1;
+#endif
 
     assert(PyFileIO_Check(oself));
     if (self->fd >= 0) {
@@ -291,6 +295,14 @@ fileio_init(PyObject *oself, PyObject *a
             self->writable = 1;
             flags |= O_EXCL | O_CREAT;
             break;
+        case 'e':
+            cloexec = 1;
+#ifdef MS_WINDOWS
+            flags |= O_NOINHERIT;
+#elif defined(O_CLOEXEC) && defined(HAVE_FCNTL_H)
+            flags |= O_CLOEXEC;
+#endif
+            break;
         case 'r':
             if (rwa)
                 goto bad_mode;
@@ -360,6 +372,15 @@ fileio_init(PyObject *oself, PyObject *a
             goto error;
         }
 
+#if !defined(MS_WINDOWS) && !defined(HAVE_FCNTL_H)
+        if (cloexec) {
+            PyErr_SetString(PyExc_NotImplementedError,
+                    "close-on-exec ('e' mode) is not supported "
+                    "by your platform");
+            goto error;
+        }
+#endif
+
         errno = 0;
         if (opener == Py_None) {
             Py_BEGIN_ALLOW_THREADS
@@ -369,10 +390,35 @@ fileio_init(PyObject *oself, PyObject *a
             else
 #endif
                 self->fd = open(name, flags, 0666);
+            if (cloexec) {
+                int fd_flags;
+#if !defined(MS_WINDOWS) && defined(O_CLOEXEC) && defined(HAVE_FCNTL_H)
+                if (cloexec_works != 1) {
+                    fd_flags = fcntl(fd, F_GETFD);
+                    if (cloexec_works == -1)
+                        cloexec_works = (fd_flags & FD_CLOEXEC);
+                    if (!cloexec_works) {
+                        fd_flags |= FD_CLOEXEC;
+                        fd_flags = fcntl(fd, F_SETFD, fd_flags);
+                    }
+                }
+#elif !defined(MS_WINDOWS) && defined(HAVE_FCNTL_H)
+                fd_flags = fcntl(fd, F_GETFD);
+                fd_flags |= FD_CLOEXEC;
+                fd_flags = fcntl(fd, F_SETFD, fd_flags);
+#endif
+            }
             Py_END_ALLOW_THREADS
         } else {
-            PyObject *fdobj = PyObject_CallFunction(
-                                  opener, "Oi", nameobj, flags);
+            PyObject *fdobj;
+
+            if (cloexec) {
+                PyErr_SetString(PyExc_ValueError,
+                        "'e' mode cannot be used with an opener");
+                goto error;
+            }
+
+            fdobj = PyObject_CallFunction(opener, "Oi", nameobj, flags);
             if (fdobj == NULL)
                 goto error;
             if (!PyLong_Check(fdobj)) {