diff -r 85b2aa520c84 -r 9e03e149be3b Doc/library/os.rst
--- a/Doc/library/os.rst	Sat Feb 28 10:46:00 2015 -0500
+++ b/Doc/library/os.rst	Thu Mar 19 14:10:29 2015 -0500
@@ -219,6 +219,18 @@
    .. versionadded:: 3.2
 
 
+.. function:: get_shell_executable()
+
+   Return  a  path   to  the  standard  system   shell  executable  --
+   :command:`sh`  program on  POSIX  (default: :const:`'/bin/sh'`)  or
+   :envvar:`ComSpec`   command   processor    on   Windows   (default:
+   :file:`%SystemRoot%\\system32\\cmd.exe`).
+
+   Availability: Unix, Windows
+
+   .. versionadded:: 3.5
+
+
 .. function:: getegid()
 
    Return the effective group id of the current process.  This corresponds to the
diff -r 85b2aa520c84 -r 9e03e149be3b Lib/os.py
--- a/Lib/os.py	Sat Feb 28 10:46:00 2015 -0500
+++ b/Lib/os.py	Thu Mar 19 14:10:29 2015 -0500
@@ -616,6 +616,32 @@
     return path_list.split(pathsep)
 
 
+if sys.platform == "win32":
+    def get_shell_executable():
+        """Return path to the command processor specified by %ComSpec%.
+
+        Default: %SystemRoot%\system32\cmd.exe
+        """
+        return (environ.get('ComSpec') or
+                path.join(environ.get('SystemRoot', r'C:\Windows'),
+                          r'system32\cmd.exe'))
+else: # POSIX
+    def get_shell_executable():
+        """Return path to the standard system shell executable.
+
+        Default: '/bin/sh'
+        """
+        for dirpath in defpath.split(pathsep):
+            if dirpath: # exclude '' (cwd)
+                sh = path.join(dirpath, 'sh')
+                if access(sh, F_OK | X_OK) and path.isfile(sh):
+                    #NOTE: allow symlinks e.g., /bin/sh on Ubuntu may be dash
+                    return sh
+        # normally, we should not get here, defpath should contain the
+        # path to the standard shell
+        return '/bin/sh'
+
+
 # Change environ to automatically call putenv(), unsetenv if they exist.
 from _collections_abc import MutableMapping
 
diff -r 85b2aa520c84 -r 9e03e149be3b Lib/test/test_os.py
--- a/Lib/test/test_os.py	Sat Feb 28 10:46:00 2015 -0500
+++ b/Lib/test/test_os.py	Thu Mar 19 14:10:29 2015 -0500
@@ -760,6 +760,35 @@
         self.assertTrue(cm.exception.__suppress_context__)
 
 
+class ShellExecutableTests(unittest.TestCase):
+    # test os.get_shell_executable()
+    def _test_get_shell_executable(self, env):
+        saved_environ = os.environ
+        try:
+            os.environ = env # test with env environment
+            sh = os.get_shell_executable()
+            self.assertTrue(sh) # not empty, not None
+            self.assertTrue(os.path.exists(sh))
+            option = "/c" if sys.platform == 'win32' else "-c"
+            #NOTE: `exit` should work even with an empty environment
+            self.assertEqual(subprocess.call([sh, option, "exit 5"]), 5)
+        finally:
+            os.environ = saved_environ
+
+    def test_get_shell_executable(self):
+        self._test_get_shell_executable(os.environ)
+
+    def test_get_shell_executable_invalid_nonempty_path(self):
+        env = {'SystemRoot': os.environ.get('SystemRoot'),
+               'PATH': '\0'}
+        self._test_get_shell_executable(env)
+
+    @unittest.skipIf(sys.platform == 'win32',
+                     "Empty env. is not supported on Win32")
+    def test_get_shell_executable_empty_environment(self):
+        self._test_get_shell_executable({})
+
+
 class WalkTests(unittest.TestCase):
     """Tests for os.walk()."""