text: # subprocess - Subprocesses with accessible I/O streams
  #
  # For more information about this module, see PEP 324.
  #
  # This module should remain compatible with Python 2.2, see PEP 291.
  #
  # Copyright (c) 2003-2005 by Peter Astrand <astrand@lysator.liu.se>
  #
  # Licensed to PSF under a Contributor Agreement.
  # See http://www.python.org/2.4/license for licensing details.
  
  r"""subprocess - Subprocesses with accessible I/O streams
  
  This module allows you to spawn processes, connect to their
  input/output/error pipes, and obtain their return codes.  This module
  intends to replace several other, older modules and functions, like:
  
  os.system
  os.spawn*
  os.popen*
  popen2.*
  commands.*
  
  Information about how the subprocess module can be used to replace these
  modules and functions can be found below.
  
  
  
  Using the subprocess module
  ===========================
  This module defines one class called Popen:
  
  class Popen(args, bufsize=0, executable=None,
              stdin=None, stdout=None, stderr=None,
              preexec_fn=None, close_fds=False, shell=False,
              cwd=None, env=None, universal_newlines=False,
              startupinfo=None, creationflags=0):
  
  
  Arguments are:
  
  args should be a string, or a sequence of program arguments.  The
  program to execute is normally the first item in the args sequence or
  string, but can be explicitly set by using the executable argument.
  
  On UNIX, with shell=False (default): In this case, the Popen class
  uses os.execvp() to execute the child program.  args should normally
  be a sequence.  A string will be treated as a sequence with the string
  as the only item (the program to execute).
  
  On UNIX, with shell=True: If args is a string, it specifies the
  command string to execute through the shell.  If args is a sequence,
  the first item specifies the command string, and any additional items
  will be treated as additional shell arguments.
  
  On Windows: the Popen class uses CreateProcess() to execute the child
  program, which operates on strings.  If args is a sequence, it will be
  converted to a string using the list2cmdline method.  Please note that
  not all MS Windows applications interpret the command line the same
  way: The list2cmdline is designed for applications using the same
  rules as the MS C runtime.
  
  bufsize, if given, has the same meaning as the corresponding argument
  to the built-in open() function: 0 means unbuffered, 1 means line
  buffered, any other positive value means use a buffer of
  (approximately) that size.  A negative bufsize means to use the system
  default, which usually means fully buffered.  The default value for
  bufsize is 0 (unbuffered).
  
  stdin, stdout and stderr specify the executed programs' standard
  input, standard output and standard error file handles, respectively.
  Valid values are PIPE, an existing file descriptor (a positive
  integer), an existing file object, and None.  PIPE indicates that a
  new pipe to the child should be created.  With None, no redirection
  will occur; the child's file handles will be inherited from the
  parent.  Additionally, stderr can be STDOUT, which indicates that the
  stderr data from the applications should be captured into the same
  file handle as for stdout.
  
  If preexec_fn is set to a callable object, this object will be called
  in the child process just before the child is executed.
  
  If close_fds is true, all file descriptors except 0, 1 and 2 will be
  closed before the child process is executed.
  
  if shell is true, the specified command will be executed through the
  shell.
  
  If cwd is not None, the current directory will be changed to cwd
  before the child is executed.
  
  If env is not None, it defines the environment variables for the new
  process.
  
  If universal_newlines is true, the file objects stdout and stderr are
  opened as a text files, but lines may be terminated by any of '\n',
  the Unix end-of-line convention, '\r', the Macintosh convention or
  '\r\n', the Windows convention.  All of these external representations
  are seen as '\n' by the Python program.  Note: This feature is only
  available if Python is built with universal newline support (the
  default).  Also, the newlines attribute of the file objects stdout,
  stdin and stderr are not updated by the communicate() method.
  
  The startupinfo and creationflags, if given, will be passed to the
  underlying CreateProcess() function.  They can specify things such as
  appearance of the main window and priority for the new process.
  (Windows only)
  
  
  This module also defines some shortcut functions:
  
  call(*popenargs, **kwargs):
      Run command with arguments.  Wait for command to complete, then
      return the returncode attribute.
  
      The arguments are the same as for the Popen constructor.  Example:
  
      retcode = call(["ls", "-l"])
  
  check_call(*popenargs, **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 returncode attribute.
  
      The arguments are the same as for the Popen constructor.  Example:
  
      check_call(["ls", "-l"])
  
  check_output(*popenargs, **kwargs):
      Run command with arguments and return its output as a byte string.
  
      If the exit code was non-zero it raises a CalledProcessError.  The
      CalledProcessError object will have the return code in the returncode
      attribute and output in the output attribute.
  
      The arguments are the same as for the Popen constructor.  Example:
  
      output = check_output(["ls", "-l", "/dev/null"])
  
  
  Exceptions
  ----------
  Exceptions raised in the child process, before the new program has
  started to execute, will be re-raised in the parent.  Additionally,
  the exception object will have one extra attribute called
  'child_traceback', which is a string containing traceback information
  from the childs point of view.
  
  The most common exception raised is OSError.  This occurs, for
  example, when trying to execute a non-existent file.  Applications
  should prepare for OSErrors.
  
  A ValueError will be raised if Popen is called with invalid arguments.
  
  check_call() and check_output() will raise CalledProcessError, if the
  called process returns a non-zero return code.
  
  
  Security
  --------
  Unlike some other popen functions, this implementation will never call
  /bin/sh implicitly.  This means that all characters, including shell
  metacharacters, can safely be passed to child processes.
  
  
  Popen objects
  =============
  Instances of the Popen class have the following methods:
  
  poll()
      Check if child process has terminated.  Returns returncode
      attribute.
  
  wait()
      Wait for child process to terminate.  Returns returncode attribute.
  
  communicate(input=None)
      Interact with process: Send data to stdin.  Read data from stdout
      and stderr, until end-of-file is reached.  Wait for process to
      terminate.  The optional input argument should be a string to be
      sent to the child process, or None, if no data should be sent to
      the child.
  
      communicate() returns a tuple (stdout, stderr).
  
      Note: The data read is buffered in memory, so do not use this
      method if the data size is large or unlimited.
  
  The following attributes are also available:
  
  stdin
      If the stdin argument is PIPE, this attribute is a file object
      that provides input to the child process.  Otherwise, it is None.
  
  stdout
      If the stdout argument is PIPE, this attribute is a file object
      that provides output from the child process.  Otherwise, it is
      None.
  
  stderr
      If the stderr argument is PIPE, this attribute is file object that
      provides error output from the child process.  Otherwise, it is
      None.
  
  pid
      The process ID of the child process.
  
  returncode
      The child return code.  A None value indicates that the process
      hasn't terminated yet.  A negative value -N indicates that the
      child was terminated by signal N (UNIX only).
  
  
  Replacing older functions with the subprocess module
  ====================================================
  In this section, "a ==> b" means that b can be used as a replacement
  for a.
  
  Note: All functions in this section fail (more or less) silently if
  the executed program cannot be found; this module raises an OSError
  exception.
  
  In the following examples, we assume that the subprocess module is
  imported with "from subprocess import *".
  
  
  Replacing /bin/sh shell backquote
  ---------------------------------
  output=`mycmd myarg`
  ==>
  output = Popen(["mycmd", "myarg"], stdout=PIPE).communicate()[0]
  
  
  Replacing shell pipe line
  -------------------------
  output=`dmesg | grep hda`
  ==>
  p1 = Popen(["dmesg"], stdout=PIPE)
  p2 = Popen(["grep", "hda"], stdin=p1.stdout, stdout=PIPE)
  output = p2.communicate()[0]
  
  
  Replacing os.system()
  ---------------------
  sts = os.system("mycmd" + " myarg")
  ==>
  p = Popen("mycmd" + " myarg", shell=True)
  pid, sts = os.waitpid(p.pid, 0)
  
  Note:
  
  * Calling the program through the shell is usually not required.
  
  * It's easier to look at the returncode attribute than the
    exitstatus.
  
  A more real-world example would look like this:
  
  try:
      retcode = call("mycmd" + " myarg", shell=True)
      if retcode < 0:
          print >>sys.stderr, "Child was terminated by signal", -retcode
      else:
          print >>sys.stderr, "Child returned", retcode
  except OSError, e:
      print >>sys.stderr, "Execution failed:", e
  
  
  Replacing os.spawn*
  -------------------
  P_NOWAIT example:
  
  pid = os.spawnlp(os.P_NOWAIT, "/bin/mycmd", "mycmd", "myarg")
  ==>
  pid = Popen(["/bin/mycmd", "myarg"]).pid
  
  
  P_WAIT example:
  
  retcode = os.spawnlp(os.P_WAIT, "/bin/mycmd", "mycmd", "myarg")
  ==>
  retcode = call(["/bin/mycmd", "myarg"])
  
  
  Vector example:
  
  os.spawnvp(os.P_NOWAIT, path, args)
  ==>
  Popen([path] + args[1:])
  
  
  Environment example:
  
  os.spawnlpe(os.P_NOWAIT, "/bin/mycmd", "mycmd", "myarg", env)
  ==>
  Popen(["/bin/mycmd", "myarg"], env={"PATH": "/usr/bin"})
  
  
  Replacing os.popen*
  -------------------
  pipe = os.popen("cmd", mode='r', bufsize)
  ==>
  pipe = Popen("cmd", shell=True, bufsize=bufsize, stdout=PIPE).stdout
  
  pipe = os.popen("cmd", mode='w', bufsize)
  ==>
  pipe = Popen("cmd", shell=True, bufsize=bufsize, stdin=PIPE).stdin
  
  
  (child_stdin, child_stdout) = os.popen2("cmd", mode, bufsize)
  ==>
  p = Popen("cmd", shell=True, bufsize=bufsize,
            stdin=PIPE, stdout=PIPE, close_fds=True)
  (child_stdin, child_stdout) = (p.stdin, p.stdout)
  
  
  (child_stdin,
   child_stdout,
   child_stderr) = os.popen3("cmd", mode, bufsize)
  ==>
  p = Popen("cmd", shell=True, bufsize=bufsize,
            stdin=PIPE, stdout=PIPE, stderr=PIPE, close_fds=True)
  (child_stdin,
   child_stdout,
   child_stderr) = (p.stdin, p.stdout, p.stderr)
  
  
  (child_stdin, child_stdout_and_stderr) = os.popen4("cmd", mode,
                                                     bufsize)
  ==>
  p = Popen("cmd", shell=True, bufsize=bufsize,
            stdin=PIPE, stdout=PIPE, stderr=STDOUT, close_fds=True)
  (child_stdin, child_stdout_and_stderr) = (p.stdin, p.stdout)
  
  On Unix, os.popen2, os.popen3 and os.popen4 also accept a sequence as
  the command to execute, in which case arguments will be passed
  directly to the program without shell intervention.  This usage can be
  replaced as follows:
  
  (child_stdin, child_stdout) = os.popen2(["/bin/ls", "-l"], mode,
                                          bufsize)
  ==>
  p = Popen(["/bin/ls", "-l"], bufsize=bufsize, stdin=PIPE, stdout=PIPE)
  (child_stdin, child_stdout) = (p.stdin, p.stdout)
  
  Return code handling translates as follows:
  
  pipe = os.popen("cmd", 'w')
  ...
  rc = pipe.close()
  if rc is not None and rc % 256:
      print "There were some errors"
  ==>
  process = Popen("cmd", 'w', shell=True, stdin=PIPE)
  ...
  process.stdin.close()
  if process.wait() != 0:
      print "There were some errors"
  
  
  Replacing popen2.*
  ------------------
  (child_stdout, child_stdin) = popen2.popen2("somestring", bufsize, mode)
  ==>
  p = Popen(["somestring"], shell=True, bufsize=bufsize
            stdin=PIPE, stdout=PIPE, close_fds=True)
  (child_stdout, child_stdin) = (p.stdout, p.stdin)
  
  On Unix, popen2 also accepts a sequence as the command to execute, in
  which case arguments will be passed directly to the program without
  shell intervention.  This usage can be replaced as follows:
  
  (child_stdout, child_stdin) = popen2.popen2(["mycmd", "myarg"], bufsize,
                                              mode)
  ==>
  p = Popen(["mycmd", "myarg"], bufsize=bufsize,
            stdin=PIPE, stdout=PIPE, close_fds=True)
  (child_stdout, child_stdin) = (p.stdout, p.stdin)
  
  The popen2.Popen3 and popen2.Popen4 basically works as subprocess.Popen,
  except that:
  
  * subprocess.Popen raises an exception if the execution fails
  * the capturestderr argument is replaced with the stderr argument.
  * stdin=PIPE and stdout=PIPE must be specified.
  * popen2 closes all filedescriptors by default, but you have to specify
    close_fds=True with subprocess.Popen.
  """
  
  import sys
  mswindows = (sys.platform == "win32")
  
  import os
  import types
  import traceback
  import gc
  import signal
  import errno
  
  try:
      set
  except NameError:
      from sets import Set as set
  
  # Exception classes used by this module.
  
  
  class CalledProcessError(Exception):
  
      """This exception is raised when a process run by check_call() or
      check_output() returns a non-zero exit status.
      The exit status will be stored in the returncode attribute;
      check_output() will also store the output in the output attribute.
      """
  
      def __init__(self, returncode, cmd, output=None):
          self.returncode = returncode
          self.cmd = cmd
          self.output = output
  
      def __str__(self):
          return "Command '%s' returned non-zero exit status %d" % (
              self.cmd, self.returncode)
  
  
  if mswindows:
      import threading
      import msvcrt
      import _subprocess
  
      class STARTUPINFO:
          dwFlags = 0
          hStdInput = None
          hStdOutput = None
          hStdError = None
          wShowWindow = 0
  
      class pywintypes:
          error = IOError
  else:
      import select
      _has_poll = hasattr(select, 'poll')
      import fcntl
      import pickle
  
      # When select or poll has indicated that the file is writable,
      # we can write up to _PIPE_BUF bytes without risk of blocking.
      # POSIX defines PIPE_BUF as >= 512.
      _PIPE_BUF = getattr(select, 'PIPE_BUF', 512)
  
  
  __all__ = ["Popen", "PIPE", "STDOUT", "call", "check_call",
             "check_output", "CalledProcessError"]
  
  if mswindows:
      from _subprocess import CREATE_NEW_CONSOLE, CREATE_NEW_PROCESS_GROUP, \
          STD_INPUT_HANDLE, STD_OUTPUT_HANDLE, \
          STD_ERROR_HANDLE, SW_HIDE, \
          STARTF_USESTDHANDLES, STARTF_USESHOWWINDOW
  
      __all__.extend(["CREATE_NEW_CONSOLE", "CREATE_NEW_PROCESS_GROUP",
                      "STD_INPUT_HANDLE", "STD_OUTPUT_HANDLE",
                      "STD_ERROR_HANDLE", "SW_HIDE",
                      "STARTF_USESTDHANDLES", "STARTF_USESHOWWINDOW"])
  try:
      MAXFD = os.sysconf("SC_OPEN_MAX")
  except:
      MAXFD = 256
  
  _active = []
  
  
  def _cleanup():
      for inst in _active[:]:
          res = inst._internal_poll(_deadstate=sys.maxint)
          if res is not None:
              try:
                  _active.remove(inst)
              except ValueError:
                  # This can happen if two threads create a new Popen instance.
                  # It's harmless that it was already removed, so ignore.
                  pass
  
  PIPE = -1
  STDOUT = -2
  
  
  def _eintr_retry_call(func, *args):
      while True:
          try:
              return func(*args)
          except (OSError, IOError), e:
              if e.errno == errno.EINTR:
                  continue
              raise
  
  
  def call(*popenargs, **kwargs):
      """Run command with arguments.  Wait for command to complete, then
      return the returncode attribute.
  
      The arguments are the same as for the Popen constructor.  Example:
  
      retcode = call(["ls", "-l"])
      """
      return Popen(*popenargs, **kwargs).wait()
  
  
  def check_call(*popenargs, **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 returncode attribute.
  
      The arguments are the same as for the Popen constructor.  Example:
  
      check_call(["ls", "-l"])
      """
      retcode = call(*popenargs, **kwargs)
      if retcode:
          cmd = kwargs.get("args")
          if cmd is None:
              cmd = popenargs[0]
          raise CalledProcessError(retcode, cmd)
      return 0
  
  
  def check_output(*popenargs, **kwargs):
      r"""Run command with arguments and return its output as a byte string.
  
      If the exit code was non-zero it raises a CalledProcessError.  The
      CalledProcessError object will have the return code in the returncode
      attribute and output in the output attribute.
  
      The arguments are the same as for the Popen constructor.  Example:
  
      >>> check_output(["ls", "-l", "/dev/null"])
      'crw-rw-rw- 1 root root 1, 3 Oct 18  2007 /dev/null\n'
  
      The stdout argument is not allowed as it is used internally.
      To capture standard error in the result, use stderr=STDOUT.
  
      >>> check_output(["/bin/sh", "-c",
      ...               "ls -l non_existent_file ; exit 0"],
      ...              stderr=STDOUT)
      'ls: non_existent_file: No such file or directory\n'
      """
      if 'stdout' in kwargs:
          raise ValueError('stdout argument not allowed, it will be overridden.')
      process = Popen(stdout=PIPE, *popenargs, **kwargs)
      output, unused_err = process.communicate()
      retcode = process.poll()
      if retcode:
          cmd = kwargs.get("args")
          if cmd is None:
              cmd = popenargs[0]
          raise CalledProcessError(retcode, cmd, output=output)
      return output
  
  
  def list2cmdline(seq):
      """
      Translate a sequence of arguments into a command line
      string, using the same rules as the MS C runtime:
  
      1) Arguments are delimited by white space, which is either a
         space or a tab.
  
      2) A string surrounded by double quotation marks is
         interpreted as a single argument, regardless of white space
         contained within.  A quoted string can be embedded in an
         argument.
  
      3) A double quotation mark preceded by a backslash is
         interpreted as a literal double quotation mark.
  
      4) Backslashes are interpreted literally, unless they
         immediately precede a double quotation mark.
  
      5) If backslashes immediately precede a double quotation mark,
         every pair of backslashes is interpreted as a literal
         backslash.  If the number of backslashes is odd, the last
         backslash escapes the next double quotation mark as
         described in rule 3.
      """
  
      # See
      # http://msdn.microsoft.com/en-us/library/17w5ykft.aspx
      # or search http://msdn.microsoft.com for
      # "Parsing C++ Command-Line Arguments"
      result = []
      needquote = False
      for arg in seq:
          bs_buf = []
  
          # Add a space to separate this argument from the others
          if result:
              result.append(' ')
  
          needquote = (" " in arg) or ("\t" in arg) or not arg
          if needquote:
              result.append('"')
  
          for c in arg:
              if c == '\\':
                  # Don't know if we need to double yet.
                  bs_buf.append(c)
              elif c == '"':
                  # Double backslashes.
                  result.append('\\' * len(bs_buf) * 2)
                  bs_buf = []
                  result.append('\\"')
              else:
                  # Normal char
                  if bs_buf:
                      result.extend(bs_buf)
                      bs_buf = []
                  result.append(c)
  
          # Add remaining backslashes, if any.
          if bs_buf:
              result.extend(bs_buf)
  
          if needquote:
              result.extend(bs_buf)
              result.append('"')
  
      return ''.join(result)
  
  
  class Popen(object):
  
      def __init__(self, args, bufsize=0, executable=None,
                   stdin=None, stdout=None, stderr=None,
                   preexec_fn=None, close_fds=False, shell=False,
                   cwd=None, env=None, universal_newlines=False,
                   startupinfo=None, creationflags=0):
          """Create new Popen instance."""
          _cleanup()
  
          self._child_created = False
          if not isinstance(bufsize, (int, long)):
              raise TypeError("bufsize must be an integer")
  
          if mswindows:
              if preexec_fn is not None:
                  raise ValueError("preexec_fn is not supported on Windows "
                                   "platforms")
              if close_fds and (stdin is not None or stdout is not None or
                                stderr is not None):
                  raise ValueError("close_fds is not supported on Windows "
                                   "platforms if you redirect "
                                   "stdin/stdout/stderr")
          else:
              # POSIX
              if startupinfo is not None:
                  raise ValueError("startupinfo is only supported on Windows "
                                   "platforms")
              if creationflags != 0:
                  raise ValueError("creationflags is only supported on Windows "
                                   "platforms")
  
          self.stdin = None
          self.stdout = None
          self.stderr = None
          self.pid = None
          self.returncode = None
          self.universal_newlines = universal_newlines
  
          # Input and output objects. The general principle is like
          # this:
          #
          # Parent                   Child
          # ------                   -----
          # p2cwrite   ---stdin--->  p2cread
          # c2pread    <--stdout---  c2pwrite
          # errread    <--stderr---  errwrite
          #
          # On POSIX, the child objects are file descriptors.  On
          # Windows, these are Windows file handles.  The parent objects
          # are file descriptors on both platforms.  The parent objects
          # are None when not using PIPEs. The child objects are None
          # when not redirecting.
  
          (p2cread, p2cwrite,
           c2pread, c2pwrite,
           errread, errwrite) = self._get_handles(stdin, stdout, stderr)
  
          self._execute_child(args, executable, preexec_fn, close_fds,
                              cwd, env, universal_newlines,
                              startupinfo, creationflags, shell,
                              p2cread, p2cwrite,
                              c2pread, c2pwrite,
                              errread, errwrite)
  
          if mswindows:
              if p2cwrite is not None:
                  p2cwrite = msvcrt.open_osfhandle(p2cwrite.Detach(), 0)
              if c2pread is not None:
                  c2pread = msvcrt.open_osfhandle(c2pread.Detach(), 0)
              if errread is not None:
                  errread = msvcrt.open_osfhandle(errread.Detach(), 0)
  
          if p2cwrite is not None:
              self.stdin = os.fdopen(p2cwrite, 'wb', bufsize)
          if c2pread is not None:
              if universal_newlines:
                  self.stdout = os.fdopen(c2pread, 'rU', bufsize)
              else:
                  self.stdout = os.fdopen(c2pread, 'rb', bufsize)
          if errread is not None:
              if universal_newlines:
                  self.stderr = os.fdopen(errread, 'rU', bufsize)
              else:
                  self.stderr = os.fdopen(errread, 'rb', bufsize)
  
      def _translate_newlines(self, data):
          data = data.replace("\r\n", "\n")
          data = data.replace("\r", "\n")
          return data
  
      def __del__(self, _maxint=sys.maxint, _active=_active):
          # If __init__ hasn't had a chance to execute (e.g. if it
          # was passed an undeclared keyword argument), we don't
          # have a _child_created attribute at all.
          if not getattr(self, '_child_created', False):
              # We didn't get to successfully create a child process.
              return
          # In case the child hasn't been waited on, check if it's done.
          self._internal_poll(_deadstate=_maxint)
          if self.returncode is None and _active is not None:
              # Child is still running, keep us alive until we can wait on it.
              _active.append(self)
  
      def communicate(self, input=None):
          """Interact with process: Send data to stdin.  Read data from
          stdout and stderr, until end-of-file is reached.  Wait for
          process to terminate.  The optional input argument should be a
          string to be sent to the child process, or None, if no data
          should be sent to the child.
  
          communicate() returns a tuple (stdout, stderr)."""
  
          # Optimization: If we are only using one pipe, or no pipe at
          # all, using select() or threads is unnecessary.
          if [self.stdin, self.stdout, self.stderr].count(None) >= 2:
              stdout = None
              stderr = None
              if self.stdin:
                  if input:
                      try:
                          self.stdin.write(input)
                      except IOError, e:
                          if e.errno != errno.EPIPE and e.errno != errno.EINVAL:
                              raise
                  self.stdin.close()
              elif self.stdout:
                  stdout = _eintr_retry_call(self.stdout.read)
                  self.stdout.close()
              elif self.stderr:
                  stderr = _eintr_retry_call(self.stderr.read)
                  self.stderr.close()
              self.wait()
              return (stdout, stderr)
  
          return self._communicate(input)
  
      def poll(self):
          return self._internal_poll()
  
      if mswindows:
          #
          # Windows methods
          #
          def _get_handles(self, stdin, stdout, stderr):
              """Construct and return tuple with IO objects:
              p2cread, p2cwrite, c2pread, c2pwrite, errread, errwrite
              """
              if stdin is None and stdout is None and stderr is None:
                  return (None, None, None, None, None, None)
  
              p2cread, p2cwrite = None, None
              c2pread, c2pwrite = None, None
              errread, errwrite = None, None
  
              if stdin is None:
                  p2cread = _subprocess.GetStdHandle(
                      _subprocess.STD_INPUT_HANDLE)
                  if p2cread is None:
                      p2cread, _ = _subprocess.CreatePipe(None, 0)
              elif stdin == PIPE:
                  p2cread, p2cwrite = _subprocess.CreatePipe(None, 0)
              elif isinstance(stdin, int):
                  p2cread = msvcrt.get_osfhandle(stdin)
              else:
                  # Assuming file-like object
                  p2cread = msvcrt.get_osfhandle(stdin.fileno())
              p2cread = self._make_inheritable(p2cread)
  
              if stdout is None:
                  c2pwrite = _subprocess.GetStdHandle(
                      _subprocess.STD_OUTPUT_HANDLE)
                  if c2pwrite is None:
                      _, c2pwrite = _subprocess.CreatePipe(None, 0)
              elif stdout == PIPE:
                  c2pread, c2pwrite = _subprocess.CreatePipe(None, 0)
              elif isinstance(stdout, int):
                  c2pwrite = msvcrt.get_osfhandle(stdout)
              else:
                  # Assuming file-like object
                  c2pwrite = msvcrt.get_osfhandle(stdout.fileno())
              c2pwrite = self._make_inheritable(c2pwrite)
  
              if stderr is None:
                  errwrite = _subprocess.GetStdHandle(
                      _subprocess.STD_ERROR_HANDLE)
                  if errwrite is None:
                      _, errwrite = _subprocess.CreatePipe(None, 0)
              elif stderr == PIPE:
                  errread, errwrite = _subprocess.CreatePipe(None, 0)
              elif stderr == STDOUT:
                  errwrite = c2pwrite
              elif isinstance(stderr, int):
                  errwrite = msvcrt.get_osfhandle(stderr)
              else:
                  # Assuming file-like object
                  errwrite = msvcrt.get_osfhandle(stderr.fileno())
              errwrite = self._make_inheritable(errwrite)
  
              return (p2cread, p2cwrite,
                      c2pread, c2pwrite,
                      errread, errwrite)
  
          def _make_inheritable(self, handle):
              """Return a duplicate of handle, which is inheritable"""
              return _subprocess.DuplicateHandle(
                  _subprocess.GetCurrentProcess(),
                  handle,
                  _subprocess.GetCurrentProcess(),
                  0,
                  1,
                  _subprocess.DUPLICATE_SAME_ACCESS
              )
  
          def _find_w9xpopen(self):
              """Find and return absolut path to w9xpopen.exe"""
              w9xpopen = os.path.join(
                  os.path.dirname(_subprocess.GetModuleFileName(0)),
                  "w9xpopen.exe")
              if not os.path.exists(w9xpopen):
                  # Eeek - file-not-found - possibly an embedding
                  # situation - see if we can locate it in sys.exec_prefix
                  w9xpopen = os.path.join(os.path.dirname(sys.exec_prefix),
                                          "w9xpopen.exe")
                  if not os.path.exists(w9xpopen):
                      raise RuntimeError("Cannot locate w9xpopen.exe, which is "
                                         "needed for Popen to work with your "
                                         "shell or platform.")
              return w9xpopen
  
          def _execute_child(self, args, executable, preexec_fn, close_fds,
                             cwd, env, universal_newlines,
                             startupinfo, creationflags, shell,
                             p2cread, p2cwrite,
                             c2pread, c2pwrite,
                             errread, errwrite):
              """Execute program (MS Windows version)"""
  
              if not isinstance(args, types.StringTypes):
                  args = list2cmdline(args)
  
              # Process startup details
              if startupinfo is None:
                  startupinfo = STARTUPINFO()
              if None not in (p2cread, c2pwrite, errwrite):
                  startupinfo.dwFlags |= _subprocess.STARTF_USESTDHANDLES
                  startupinfo.hStdInput = p2cread
                  startupinfo.hStdOutput = c2pwrite
                  startupinfo.hStdError = errwrite
  
              if shell:
                  startupinfo.dwFlags |= _subprocess.STARTF_USESHOWWINDOW
                  startupinfo.wShowWindow = _subprocess.SW_HIDE
                  comspec = os.environ.get("COMSPEC", "cmd.exe")
                  args = '{} /c "{}"'.format(comspec, args)
                  if (_subprocess.GetVersion() >= 0x80000000 or
                          os.path.basename(comspec).lower() == "command.com"):
                      # Win9x, or using command.com on NT. We need to
                      # use the w9xpopen intermediate program. For more
                      # information, see KB Q150956
                      # (http://web.archive.org/web/20011105084002/http://support.microsoft.com/support/kb/articles/Q150/9/56.asp)
                      w9xpopen = self._find_w9xpopen()
                      args = '"%s" %s' % (w9xpopen, args)
                      # Not passing CREATE_NEW_CONSOLE has been known to
                      # cause random failures on win9x.  Specifically a
                      # dialog: "Your program accessed mem currently in
                      # use at xxx" and a hopeful warning about the
                      # stability of your system.  Cost is Ctrl+C wont
                      # kill children.
                      creationflags |= _subprocess.CREATE_NEW_CONSOLE
  
              # Start the process
              try:
                  try:
                      hp, ht, pid, tid = _subprocess.CreateProcess(
                          executable, args,
                          # no special
                          # security
                          None, None,
                          int(not close_fds),
                          creationflags,
                          env,
                          cwd,
                          startupinfo)
                  except pywintypes.error, e:
                      # Translate pywintypes.error to WindowsError, which is
                      # a subclass of OSError.  FIXME: We should really
                      # translate errno using _sys_errlist (or similar), but
                      # how can this be done from Python?
                      raise WindowsError(*e.args)
              finally:
                  # Child is launched. Close the parent's copy of those pipe
                  # handles that only the child should have open.  You need
                  # to make sure that no handles to the write end of the
                  # output pipe are maintained in this process or else the
                  # pipe will not close when the child process exits and the
                  # ReadFile will hang.
                  if p2cread is not None:
                      p2cread.Close()
                  if c2pwrite is not None:
                      c2pwrite.Close()
                  if errwrite is not None:
                      errwrite.Close()
  
              # Retain the process handle, but close the thread handle
              self._child_created = True
              self._handle = hp
              self.pid = pid
              ht.Close()
  
          def _internal_poll(
                  self, _deadstate=None,
                  _WaitForSingleObject=_subprocess.WaitForSingleObject,
                  _WAIT_OBJECT_0=_subprocess.WAIT_OBJECT_0,
                  _GetExitCodeProcess=_subprocess.GetExitCodeProcess
          ):
              """Check if child process has terminated.  Returns returncode
              attribute.
  
              This method is called by __del__, so it can only refer to objects
              in its local scope.
  
              """
              if self.returncode is None:
                  if _WaitForSingleObject(self._handle, 0) == _WAIT_OBJECT_0:
                      self.returncode = _GetExitCodeProcess(self._handle)
              return self.returncode
  
          def wait(self):
              """Wait for child process to terminate.  Returns returncode
              attribute."""
              if self.returncode is None:
                  _subprocess.WaitForSingleObject(self._handle,
                                                  _subprocess.INFINITE)
                  self.returncode = _subprocess.GetExitCodeProcess(self._handle)
              return self.returncode
  
          def _readerthread(self, fh, buffer):
              buffer.append(fh.read())
  
          def _communicate(self, input):
              stdout = None  # Return
              stderr = None  # Return
  
              if self.stdout:
                  stdout = []
                  stdout_thread = threading.Thread(target=self._readerthread,
                                                   args=(self.stdout, stdout))
                  stdout_thread.setDaemon(True)
                  stdout_thread.start()
              if self.stderr:
                  stderr = []
                  stderr_thread = threading.Thread(target=self._readerthread,
                                                   args=(self.stderr, stderr))
                  stderr_thread.setDaemon(True)
                  stderr_thread.start()
  
              if self.stdin:
                  if input is not None:
                      try:
                          self.stdin.write(input)
                      except IOError, e:
                          if e.errno != errno.EPIPE:
                              raise
                  self.stdin.close()
  
              if self.stdout:
                  stdout_thread.join()
              if self.stderr:
                  stderr_thread.join()
  
              # All data exchanged.  Translate lists into strings.
              if stdout is not None:
                  stdout = stdout[0]
              if stderr is not None:
                  stderr = stderr[0]
  
              # Translate newlines, if requested.  We cannot let the file
              # object do the translation: It is based on stdio, which is
              # impossible to combine with select (unless forcing no
              # buffering).
              if self.universal_newlines and hasattr(file, 'newlines'):
                  if stdout:
                      stdout = self._translate_newlines(stdout)
                  if stderr:
                      stderr = self._translate_newlines(stderr)
  
              self.wait()
              return (stdout, stderr)
  
          def send_signal(self, sig):
              """Send a signal to the process
              """
              if sig == signal.SIGTERM:
                  self.terminate()
              elif sig == signal.CTRL_C_EVENT:
                  os.kill(self.pid, signal.CTRL_C_EVENT)
              elif sig == signal.CTRL_BREAK_EVENT:
                  os.kill(self.pid, signal.CTRL_BREAK_EVENT)
              else:
                  raise ValueError("Unsupported signal: {}".format(sig))
  
          def terminate(self):
              """Terminates the process
              """
              _subprocess.TerminateProcess(self._handle, 1)
  
          kill = terminate
  
      else:
          #
          # POSIX methods
          #
          def _get_handles(self, stdin, stdout, stderr):
              """Construct and return tuple with IO objects:
              p2cread, p2cwrite, c2pread, c2pwrite, errread, errwrite
              """
              p2cread, p2cwrite = None, None
              c2pread, c2pwrite = None, None
              errread, errwrite = None, None
  
              if stdin is None:
                  pass
              elif stdin == PIPE:
                  p2cread, p2cwrite = self.pipe_cloexec()
              elif isinstance(stdin, int):
                  p2cread = stdin
              else:
                  # Assuming file-like object
                  p2cread = stdin.fileno()
  
              if stdout is None:
                  pass
              elif stdout == PIPE:
                  c2pread, c2pwrite = self.pipe_cloexec()
              elif isinstance(stdout, int):
                  c2pwrite = stdout
              else:
                  # Assuming file-like object
                  c2pwrite = stdout.fileno()
  
              if stderr is None:
                  pass
              elif stderr == PIPE:
                  errread, errwrite = self.pipe_cloexec()
              elif stderr == STDOUT:
                  errwrite = c2pwrite
              elif isinstance(stderr, int):
                  errwrite = stderr
              else:
                  # Assuming file-like object
                  errwrite = stderr.fileno()
  
              return (p2cread, p2cwrite,
                      c2pread, c2pwrite,
                      errread, errwrite)
  
          def _set_cloexec_flag(self, fd, cloexec=True):
              try:
                  cloexec_flag = fcntl.FD_CLOEXEC
              except AttributeError:
                  cloexec_flag = 1
  
              old = fcntl.fcntl(fd, fcntl.F_GETFD)
              if cloexec:
                  fcntl.fcntl(fd, fcntl.F_SETFD, old | cloexec_flag)
              else:
                  fcntl.fcntl(fd, fcntl.F_SETFD, old & ~cloexec_flag)
  
          def pipe_cloexec(self):
              """Create a pipe with FDs set CLOEXEC."""
              # Pipes' FDs are set CLOEXEC by default because we don't want them
              # to be inherited by other subprocesses: the CLOEXEC flag is
              # removed from the child's FDs by _dup2(), between fork() and
              # exec().
              # This is not atomic: we would need the pipe2() syscall for that.
              r, w = os.pipe()
              self._set_cloexec_flag(r)
              self._set_cloexec_flag(w)
              return r, w
  
          def _close_fds(self, but):
              if hasattr(os, 'closerange'):
                  os.closerange(3, but)
                  os.closerange(but + 1, MAXFD)
              else:
                  for i in xrange(3, MAXFD):
                      if i == but:
                          continue
                      try:
                          os.close(i)
                      except:
                          pass
  
          def _execute_child(self, args, executable, preexec_fn, close_fds,
                             cwd, env, universal_newlines,
                             startupinfo, creationflags, shell,
                             p2cread, p2cwrite,
                             c2pread, c2pwrite,
                             errread, errwrite):
              """Execute program (POSIX version)"""
  
              if isinstance(args, types.StringTypes):
                  args = [args]
              else:
                  args = list(args)
  
              if shell:
                  args = ["/bin/sh", "-c"] + args
                  if executable:
                      args[0] = executable
  
              if executable is None:
                  executable = args[0]
  
              # For transferring possible exec failure from child to parent
              # The first char specifies the exception type: 0 means
              # OSError, 1 means some other error.
              errpipe_read, errpipe_write = self.pipe_cloexec()
              try:
                  try:
                      gc_was_enabled = gc.isenabled()
                      # Disable gc to avoid bug where gc -> file_dealloc ->
                      # write to stderr -> hang.
                      # http://bugs.python.org/issue1336
                      gc.disable()
                      try:
                          self.pid = os.fork()
                      except:
                          if gc_was_enabled:
                              gc.enable()
                          raise
                      self._child_created = True
                      if self.pid == 0:
                          # Child
                          try:
                              # Close parent's pipe ends
                              if p2cwrite is not None:
                                  os.close(p2cwrite)
                              if c2pread is not None:
                                  os.close(c2pread)
                              if errread is not None:
                                  os.close(errread)
                              os.close(errpipe_read)
  
                              # When duping fds, if there arises a situation
                              # where one of the fds is either 0, 1 or 2, it
                              # is possible that it is overwritten (#12607).
                              if c2pwrite == 0:
                                  c2pwrite = os.dup(c2pwrite)
                              if errwrite == 0 or errwrite == 1:
                                  errwrite = os.dup(errwrite)
  
                              # Dup fds for child
                              def _dup2(a, b):
                                  # dup2() removes the CLOEXEC flag but
                                  # we must do it ourselves if dup2()
                                  # would be a no-op (issue #10806).
                                  if a == b:
                                      self._set_cloexec_flag(a, False)
                                  elif a is not None:
                                      os.dup2(a, b)
                              _dup2(p2cread, 0)
                              _dup2(c2pwrite, 1)
                              _dup2(errwrite, 2)
  
                              # Close pipe fds.  Make sure we don't close the
                              # same fd more than once, or standard fds.
                              closed = set([None])
                              for fd in [p2cread, c2pwrite, errwrite]:
                                  if fd not in closed and fd > 2:
                                      os.close(fd)
                                      closed.add(fd)
  
                              # Close all other fds, if asked for
                              if close_fds:
                                  self._close_fds(but=errpipe_write)
  
                              if cwd is not None:
                                  os.chdir(cwd)
  
                              if preexec_fn:
                                  preexec_fn()
  
                              if env is None:
                                  os.execvp(executable, args)
                              else:
                                  os.execvpe(executable, args, env)
  
                          except:
                              exc_type, exc_value, tb = sys.exc_info()
                              # Save the traceback and attach it to the exception
                              # object
                              exc_lines = traceback.format_exception(exc_type,
                                                                     exc_value,
                                                                     tb)
                              exc_value.child_traceback = ''.join(exc_lines)
                              os.write(errpipe_write, pickle.dumps(exc_value))
  
                          # This exitcode won't be reported to applications,
                          # so it really doesn't matter what we return.
                          os._exit(255)
  
                      # Parent
                      if gc_was_enabled:
                          gc.enable()
                  finally:
                      # be sure the FD is closed no matter what
                      os.close(errpipe_write)
  
                  if p2cread is not None and p2cwrite is not None:
                      os.close(p2cread)
                  if c2pwrite is not None and c2pread is not None:
                      os.close(c2pwrite)
                  if errwrite is not None and errread is not None:
                      os.close(errwrite)
  
                  # Wait for exec to fail or succeed; possibly raising exception
                  # Exception limited to 1M
                  data = _eintr_retry_call(os.read, errpipe_read, 1048576)
              finally:
                  # be sure the FD is closed no matter what
                  os.close(errpipe_read)
  
              if data != "":
                  try:
                      _eintr_retry_call(os.waitpid, self.pid, 0)
                  except OSError, e:
                      if e.errno != errno.ECHILD:
                          raise
                  child_exception = pickle.loads(data)
                  for fd in (p2cwrite, c2pread, errread):
                      if fd is not None:
                          os.close(fd)
                  raise child_exception
  
          def _handle_exitstatus(self, sts, _WIFSIGNALED=os.WIFSIGNALED,
                                 _WTERMSIG=os.WTERMSIG, _WIFEXITED=os.WIFEXITED,
                                 _WEXITSTATUS=os.WEXITSTATUS):
              # This method is called (indirectly) by __del__, so it cannot
              # refer to anything outside of its local scope."""
              if _WIFSIGNALED(sts):
                  self.returncode = -_WTERMSIG(sts)
              elif _WIFEXITED(sts):
                  self.returncode = _WEXITSTATUS(sts)
              else:
                  # Should never happen
                  raise RuntimeError("Unknown child exit status!")
  
          def _internal_poll(self, _deadstate=None, _waitpid=os.waitpid,
                             _WNOHANG=os.WNOHANG, _os_error=os.error):
              """Check if child process has terminated.  Returns returncode
              attribute.
  
              This method is called by __del__, so it cannot reference anything
              outside of the local scope (nor can any methods it calls).
  
              """
              if self.returncode is None:
                  try:
                      pid, sts = _waitpid(self.pid, _WNOHANG)
                      if pid == self.pid:
                          self._handle_exitstatus(sts)
                  except _os_error:
                      if _deadstate is not None:
                          self.returncode = _deadstate
              return self.returncode
  
          def wait(self):
              """Wait for child process to terminate.  Returns returncode
              attribute."""
              if self.returncode is None:
                  try:
                      pid, sts = _eintr_retry_call(os.waitpid, self.pid, 0)
                  except OSError, e:
                      if e.errno != errno.ECHILD:
                          raise
                      # This happens if SIGCLD is set to be ignored or waiting
                      # for child processes has otherwise been disabled for our
                      # process.  This child is dead, we can't get the status.
                      sts = 0
                  self._handle_exitstatus(sts)
              return self.returncode
  
          def _communicate(self, input):
              if self.stdin:
                  # Flush stdio buffer.  This might block, if the user has
                  # been writing to .stdin in an uncontrolled fashion.
                  self.stdin.flush()
                  if not input:
                      self.stdin.close()
  
              if _has_poll:
                  stdout, stderr = self._communicate_with_poll(input)
              else:
                  stdout, stderr = self._communicate_with_select(input)
  
              # All data exchanged.  Translate lists into strings.
              if stdout is not None:
                  stdout = ''.join(stdout)
              if stderr is not None:
                  stderr = ''.join(stderr)
  
              # Translate newlines, if requested.  We cannot let the file
              # object do the translation: It is based on stdio, which is
              # impossible to combine with select (unless forcing no
              # buffering).
              if self.universal_newlines and hasattr(file, 'newlines'):
                  if stdout:
                      stdout = self._translate_newlines(stdout)
                  if stderr:
                      stderr = self._translate_newlines(stderr)
  
              self.wait()
              return (stdout, stderr)
  
          def _communicate_with_poll(self, input):
              stdout = None  # Return
              stderr = None  # Return
              fd2file = {}
              fd2output = {}
  
              poller = select.poll()
  
              def register_and_append(file_obj, eventmask):
                  poller.register(file_obj.fileno(), eventmask)
                  fd2file[file_obj.fileno()] = file_obj
  
              def close_unregister_and_remove(fd):
                  poller.unregister(fd)
                  fd2file[fd].close()
                  fd2file.pop(fd)
  
              if self.stdin and input:
                  register_and_append(self.stdin, select.POLLOUT)
  
              select_POLLIN_POLLPRI = select.POLLIN | select.POLLPRI
              if self.stdout:
                  register_and_append(self.stdout, select_POLLIN_POLLPRI)
                  fd2output[self.stdout.fileno()] = stdout = []
              if self.stderr:
                  register_and_append(self.stderr, select_POLLIN_POLLPRI)
                  fd2output[self.stderr.fileno()] = stderr = []
  
              input_offset = 0
              while fd2file:
                  try:
                      ready = poller.poll()
                  except select.error, e:
                      if e.args[0] == errno.EINTR:
                          continue
                      raise
  
                  for fd, mode in ready:
                      if mode & select.POLLOUT:
                          chunk = input[input_offset: input_offset + _PIPE_BUF]
                          try:
                              input_offset += os.write(fd, chunk)
                          except OSError, e:
                              if e.errno == errno.EPIPE:
                                  close_unregister_and_remove(fd)
                              else:
                                  raise
                          else:
                              if input_offset >= len(input):
                                  close_unregister_and_remove(fd)
                      elif mode & select_POLLIN_POLLPRI:
                          data = os.read(fd, 4096)
                          if not data:
                              close_unregister_and_remove(fd)
                          fd2output[fd].append(data)
                      else:
                          # Ignore hang up or errors.
                          close_unregister_and_remove(fd)
  
              return (stdout, stderr)
  
          def _communicate_with_select(self, input):
              read_set = []
              write_set = []
              stdout = None  # Return
              stderr = None  # Return
  
              if self.stdin and input:
                  write_set.append(self.stdin)
              if self.stdout:
                  read_set.append(self.stdout)
                  stdout = []
              if self.stderr:
                  read_set.append(self.stderr)
                  stderr = []
  
              input_offset = 0
              while read_set or write_set:
                  try:
                      rlist, wlist, xlist = select.select(
                          read_set, write_set, [])
                  except select.error, e:
                      if e.args[0] == errno.EINTR:
                          continue
                      raise
  
                  if self.stdin in wlist:
                      chunk = input[input_offset: input_offset + _PIPE_BUF]
                      try:
                          bytes_written = os.write(self.stdin.fileno(), chunk)
                      except OSError, e:
                          if e.errno == errno.EPIPE:
                              self.stdin.close()
                              write_set.remove(self.stdin)
                          else:
                              raise
                      else:
                          input_offset += bytes_written
                          if input_offset >= len(input):
                              self.stdin.close()
                              write_set.remove(self.stdin)
  
                  if self.stdout in rlist:
                      data = os.read(self.stdout.fileno(), 1024)
                      if data == "":
                          self.stdout.close()
                          read_set.remove(self.stdout)
                      stdout.append(data)
  
                  if self.stderr in rlist:
                      data = os.read(self.stderr.fileno(), 1024)
                      if data == "":
                          self.stderr.close()
                          read_set.remove(self.stderr)
                      stderr.append(data)
  
              return (stdout, stderr)
  
          def send_signal(self, sig):
              """Send a signal to the process
              """
              os.kill(self.pid, sig)
  
          def terminate(self):
              """Terminate the process with SIGTERM
              """
              self.send_signal(signal.SIGTERM)
  
          def kill(self):
              """Kill the process with SIGKILL
              """
              self.send_signal(signal.SIGKILL)
  
  
  def _demo_posix():
      #
      # Example 1: Simple redirection: Get process list
      #
      plist = Popen(["ps"], stdout=PIPE).communicate()[0]
      print "Process list:"
      print plist
  
      #
      # Example 2: Change uid before executing child
      #
      if os.getuid() == 0:
          p = Popen(["id"], preexec_fn=lambda: os.setuid(100))
          p.wait()
  
      #
      # Example 3: Connecting several subprocesses
      #
      print "Looking for 'hda'..."
      p1 = Popen(["dmesg"], stdout=PIPE)
      p2 = Popen(["grep", "hda"], stdin=p1.stdout, stdout=PIPE)
      print repr(p2.communicate()[0])
  
      #
      # Example 4: Catch execution error
      #
      print
      print "Trying a weird file..."
      try:
          print Popen(["/this/path/does/not/exist"]).communicate()
      except OSError, e:
          if e.errno == errno.ENOENT:
              print "The file didn't exist.  I thought so..."
              print "Child traceback:"
              print e.child_traceback
          else:
              print "Error", e.errno
      else:
          print >>sys.stderr, "Gosh.  No error."
  
  
  def _demo_windows():
      #
      # Example 1: Connecting several subprocesses
      #
      print "Looking for 'PROMPT' in set output..."
      p1 = Popen("set", stdout=PIPE, shell=True)
      p2 = Popen('find "PROMPT"', stdin=p1.stdout, stdout=PIPE)
      print repr(p2.communicate()[0])
  
      #
      # Example 2: Simple execution of program
      #
      print "Executing calc..."
      p = Popen("calc")
      p.wait()
  
  
  if __name__ == "__main__":
      if mswindows:
          _demo_windows()
      else:
          _demo_posix()
  