twisted.internet.process.Process : API documentation

An operating-system Process.

This represents an operating-system process with arbitrary input/output pipes connected to it. Those pipes may represent standard input, standard output, and standard error, or any other file descriptor.

On UNIX, this is implemented using fork(), exec(), pipe() and fcntl(). These calls may not exist elsewhere so this code is not cross-platform. (also, windows can only select on sockets...)

Method	__init__	Spawn an operating-system process.
Method	writeToChild	Undocumented
Method	closeChildFD	Undocumented
Method	pauseProducing	Undocumented
Method	resumeProducing	Undocumented
Method	closeStdin	Call this to close standard input on this process.
Method	closeStdout	Undocumented
Method	closeStderr	Undocumented
Method	loseConnection	Undocumented
Method	write	Call this to write to standard input on this process.
Method	registerProducer	Call this to register producer for standard input.
Method	unregisterProducer	Call this to unregister producer for standard input.
Method	writeSequence	Call this to write to standard input on this process.
Method	childDataReceived	Undocumented
Method	processEnded	Undocumented
Method	childConnectionLost	Undocumented
Method	maybeCallProcessEnded	Call processEnded on protocol after final cleanup.
Method	_setupChild	fdmap[childFD] = parentFD

Inherited from _BaseProcess:

Method	reapProcess	Try to reap a process (without blocking) via waitpid.
Method	signalProcess	No summary
Method	__repr__	String representation of a process.
Method	_fork	Fork and then exec sub-process.
Method	_execChild	The exec() which is done in the forked child.

Inherited from Ephemeral (via _BaseProcess):

Method	__getstate__	Undocumented
Method	__setstate__	Undocumented

def __init__(self, reactor, executable, args, environment, path, proto, uid=None, gid=None, childFDs=None): (source)

Spawn an operating-system process.

This is where the hard work of disconnecting all currently open files / forking / executing the new process happens. (This is executed automatically when a Process is instantiated.)

This will also run the subprocess as a given user ID and group ID, if specified. (Implementation Note: this doesn't support all the arcane nuances of setXXuid on UNIX: it will assume that either your effective or real UID is 0.)

def _setupChild(self, fdmap): (source)

overrides twisted.internet.process._BaseProcess._setupChild

fdmap[childFD] = parentFD

The child wants to end up with 'childFD' attached to what used to be the parent's parentFD. As an example, a bash command run like 'command 2>&1' would correspond to an fdmap of {0:0, 1:1, 2:1}. 'command >foo.txt' would be {0:0, 1:os.open('foo.txt'), 2:2}.

This is accomplished in two steps:

   1. close all file descriptors that aren't values of fdmap.  This
      means 0 .. maxfds.

   2. for each childFD::

        - if fdmap[childFD] == childFD, the descriptor is already in
          place.  Make sure the CLOEXEC flag is not set, then delete
          the entry from fdmap.

        - if childFD is in fdmap.values(), then the target descriptor
          is busy. Use os.dup() to move it elsewhere, update all
          fdmap[childFD] items that point to it, then close the
          original. Then fall through to the next case.

        - now fdmap[childFD] is not in fdmap.values(), and is free.
          Use os.dup2() to move it to the right place, then close the
          original.

t.i.p.Process(_BaseProcess) : class documentation