a posix forkpty implementation for gevent - works with pexpect nicely

forkpty_wrapper.py

# Make a forkpty wrapper that works nicely with gevent.
# This only wraps the process properly, the same way gevent.os.fork() does,
# and doesn't do anything special for dealing with the pty file descriptor.
# 
# This was originally intended to work with pexpect, and does so nicely, since the
# head version of pexpect uses select.select and time.sleep in many places, effectively
# "geventifying" the expect interactions.
# 
# Other things using forkpty and doing reads and writes via the pty will need to
# take a look at doing proper gevent wrapping of operations on the fd for now.
#
# N.B. - This almost certainly does not work on windows. If it does, your code is
#        probably wrong, and the accident of it working is not to be counted on even
#        across boots on the same machine

import gevent
import os
import gevent.os
from gevent import monkey

_real_forkpty = os.forkpty

def forkpty_and_watch(callback=None, loop=None, ref=False, fork=None):
    """
    This is the same as gevent.forkpty_and_watch, except it wraps
    os.forkpty rather than os.fork.
    """
    # note result is a pair of (pid, fd)
    # the value of pid is the same as if fork ahd been called
    # fd is the appropriate pty device fd (master or slave as needed by parent or child)
    result = _real_forkpty()

    # act like gevent_fork was called
    if not result[0]:
        gevent.reinit()
        return result
    pid = result[0]

    # direct copy of fork_and_watch, transliterated for not being deep in gevent
    if pid:
        # parent
        loop = gevent.get_hub().loop
        watcher = loop.child(pid)
        gevent.os._watched_children[pid] = watcher
        watcher.start(gevent.os._on_child, watcher, callback)

    # return value is the (pid, fd) pair as forkpty() returns
    return result

# just patch forkpty as if gevent.monkey.patch_os or patch_all had done it
monkey.patch_item(os, 'forkpty', forkpty_and_watch)