Index: subprocess.py
===================================================================
RCS file: /cvsroot/python/python/dist/src/Lib/subprocess.py,v
retrieving revision 1.8
diff -u -r1.8 subprocess.py
--- subprocess.py	7 Nov 2004 14:30:34 -0000	1.8
+++ subprocess.py	23 Nov 2004 13:54:48 -0000
@@ -123,7 +123,7 @@
 (Windows only)
 
 
-This module also defines two shortcut functions:
+This module also defines three shortcut functions:
 
 call(*args, **kwargs):
     Run command with arguments.  Wait for command to complete, then
@@ -133,6 +133,15 @@
 
     retcode = call(["ls", "-l"])
 
+xcall(*args, **kwargs):
+    Run command with arguments.  Wait for command to complete.  If the
+    exit code was zero then return, otherwise raise
+    CalledProcessError.  The CalledProcessError object will have the
+    return code in the errno attribute.
+
+    The arguments are the same as for the Popen constructor.  Example:
+
+    xcall(["ls", "-l"])
 
 Exceptions
 ----------
@@ -148,6 +157,9 @@
 
 A ValueError will be raised if Popen is called with invalid arguments.
 
+xcall() will raise CalledProcessError which is a child of OSError if
+the called process returns a non-zero return code.
+
 
 Security
 --------
@@ -363,6 +375,13 @@
 import types
 import traceback
 
+# Exception classes used by this module.
+class CalledProcessError(OSError):
+    """This exception is raised when a process run by xcall() returns
+    a non-zero exit status.  The exit status will be stored in the
+    errno attribute.  Note that this exception is a subclass of
+    OSError."""
+
 if mswindows:
     import threading
     import msvcrt
@@ -393,7 +412,7 @@
     import fcntl
     import pickle
 
-__all__ = ["Popen", "PIPE", "STDOUT", "call"]
+__all__ = ["Popen", "PIPE", "STDOUT", "call", "xcall", "CalledProcessError"]
 
 try:
     MAXFD = os.sysconf("SC_OPEN_MAX")
@@ -428,6 +447,21 @@
     return Popen(*args, **kwargs).wait()
 
 
+def xcall(*args, **kwargs):
+    """Run command with arguments.  Wait for command to complete.  If
+    the exit code was zero then return, otherwise raise
+    CalledProcessError.  The CalledProcessError object will have the
+    return code in the errno attribute.
+
+    The arguments are the same as for the Popen constructor.  Example:
+
+    xcall(["ls", "-l"])
+    """
+    rc = call(*args, **kwargs)
+    if rc:
+        raise CalledProcessError(rc, "Command %s returned non zero exit status" % args[0])
+
+
 def list2cmdline(seq):
     """
     Translate a sequence of arguments into a command line
Index: test/test_subprocess.py
===================================================================
RCS file: /cvsroot/python/python/dist/src/Lib/test/test_subprocess.py,v
retrieving revision 1.15
diff -u -r1.15 test_subprocess.py
--- test/test_subprocess.py	17 Nov 2004 20:06:35 -0000	1.15
+++ test/test_subprocess.py	23 Nov 2004 13:54:48 -0000
@@ -44,6 +44,23 @@
                               "import sys; sys.exit(47)"])
         self.assertEqual(rc, 47)
 
+    def test_xcall_zero(self):
+        # xcall() function with zero return code
+        # xcall() just calls call() so we test where the two differ
+        rc = subprocess.xcall([sys.executable, "-c",
+                              "import sys; sys.exit(0)"])
+        self.assertEqual(rc, None)
+
+    def test_xcall_nonzero(self):
+        # xcall() function with non zero return code
+        try:
+            subprocess.xcall([sys.executable, "-c",
+                             "import sys; sys.exit(47)"])
+        except subprocess.CalledProcessError, e:
+            self.assertEqual(e.errno, 47)
+        else:
+            self.fail("Expected OSError")
+
     def test_call_kwargs(self):
         # call() function with keyword args
         newenv = os.environ.copy()