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diff --git a/cvs2svn_lib/process.py b/cvs2svn_lib/process.py
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+# (Be in -*- python -*- mode.)
+#
+# ====================================================================
+# Copyright (c) 2000-2008 CollabNet.  All rights reserved.
+#
+# This software is licensed as described in the file COPYING, which
+# you should have received as part of this distribution.  The terms
+# are also available at http://subversion.tigris.org/license-1.html.
+# If newer versions of this license are posted there, you may use a
+# newer version instead, at your option.
+#
+# This software consists of voluntary contributions made by many
+# individuals.  For exact contribution history, see the revision
+# history and logs, available at http://cvs2svn.tigris.org/.
+# ====================================================================
+
+"""This module contains generic utilities used by cvs2svn."""
+
+
+import subprocess
+
+from cvs2svn_lib.common import FatalError
+from cvs2svn_lib.common import CommandError
+
+
+def call_command(command, **kw):
+  """Call the specified command, checking that it exits successfully.
+
+  Raise a FatalError if the command cannot be executed, or if it exits
+  with a non-zero exit code.  Pass KW as keyword arguments to
+  subprocess.call()."""
+
+  try:
+    retcode = subprocess.call(command, **kw)
+    if retcode < 0:
+      raise FatalError(
+          'Command terminated by signal %d: "%s"'
+          % (-retcode, ' '.join(command),)
+          )
+    elif retcode > 0:
+      raise FatalError(
+          'Command failed with return code %d: "%s"'
+          % (retcode, ' '.join(command),)
+          )
+  except OSError, e:
+    raise FatalError(
+        'Command execution failed (%s): "%s"'
+        % (e, ' '.join(command),)
+        )
+
+
+class CommandFailedException(Exception):
+  """Exception raised if check_command_runs() fails."""
+
+  pass
+
+
+def check_command_runs(cmd, cmdname):
+  """Check whether the command CMD can be executed without errors.
+
+  CMD is a list or string, as accepted by subprocess.Popen().  CMDNAME
+  is the name of the command as it should be included in exception
+  error messages.
+
+  This function checks three things: (1) the command can be run
+  without throwing an OSError; (2) it exits with status=0; (3) it
+  doesn't output anything to stderr.  If any of these conditions is
+  not met, raise a CommandFailedException describing the problem."""
+
+  try:
+    pipe = subprocess.Popen(
+        cmd,
+        stdin=subprocess.PIPE,
+        stdout=subprocess.PIPE,
+        stderr=subprocess.PIPE,
+        )
+  except OSError, e:
+    raise CommandFailedException('error executing %s: %s' % (cmdname, e,))
+  pipe.stdin.close()
+  pipe.stdout.read()
+  errmsg = pipe.stderr.read()
+  status = pipe.wait()
+  if status or errmsg:
+    msg = 'error executing %s: status %s' % (cmdname, status,)
+    if errmsg:
+      msg += ', error output:\n%s' % (errmsg,)
+    raise CommandFailedException(msg)
+
+
+class PipeStream(object):
+  """A file-like object from which revision contents can be read."""
+
+  def __init__(self, pipe_command):
+    self._pipe_command_str = ' '.join(pipe_command)
+    self.pipe = subprocess.Popen(
+        pipe_command,
+        stdin=subprocess.PIPE,
+        stdout=subprocess.PIPE,
+        stderr=subprocess.PIPE,
+        )
+    self.pipe.stdin.close()
+
+  def read(self, size=None):
+    if size is None:
+      return self.pipe.stdout.read()
+    else:
+      return self.pipe.stdout.read(size)
+
+  def close(self):
+    self.pipe.stdout.close()
+    error_output = self.pipe.stderr.read()
+    exit_status = self.pipe.wait()
+    if exit_status:
+      raise CommandError(self._pipe_command_str, exit_status, error_output)
+
+