#!/usr/bin/env python

# -*- coding: utf-8 -*-

# subset of subprocess built-in module using posix_spawn rather than fork.

import os, sys

import signal

import shlex

import posix_spawn

PIPE = "42"

fsencoding = sys.getfilesystemencoding()

class Popen(object):

def __init__(self, args, stdin=None, stdout=None):

self.returncode = None

self.stdout = None

self.stdin = None

# TODO: stderr

file_actions = posix_spawn.FileActions()

if stdout is not None:

# child's stdout, child 2 parent pipe

c2pread, c2pwrite = os.pipe()

# attach child's stdout to writing en of c2p pipe

file_actions.add_dup2(c2pwrite, 1)

# close other end

file_actions.add_close(c2pread)

if stdin is not None:

# child's stdin, parent to child pipe

p2cread, p2cwrite = os.pipe()

# attach child's stdin to reading en of p2c pipe

file_actions.add_dup2(p2cread, 0)

# close other end

file_actions.add_close(p2cwrite)

args = [s.encode(fsencoding) for s in args if type(s)==str]

self.pid = posix_spawn.posix_spawnp(args[0], args, file_actions=file_actions)

if stdout is not None:

self.stdout = os.fdopen(c2pread)

os.close(c2pwrite)

if stdin is not None:

self.stdin = os.fdopen(p2cwrite, 'w')

os.close(p2cread)

def _wait(self):

if self.returncode is None:

self.returncode = os.waitpid(self.pid, 0)[1]

def communicate(self):

if self.stdin is not None:

self.stdin.close()

self.stdin = None

if self.stdout is not None:

stdoutdata = self.stdout.read()

else:

stdoutdata = ""

# TODO

stderrdata = ""

self._wait()

if self.stdout is not None:

self.stdout.close()

self.stdout = None

return (stdoutdata, stderrdata)

def wait(self):

if self.stdin is not None:

self.stdin.close()

self.stdin = None

self._wait()

if self.stdout is not None:

self.stdout.close()

self.stdout = None

return self.returncode

def poll(self):

if self.returncode is None:

pid, ret = os.waitpid(self.pid, os.WNOHANG)

if (pid, ret) != (0, 0):

self.returncode = ret

if self.stdin is not None:

self.stdin.close()

self.stdin = None

if self.stdout is not None:

self.stdout.close()

self.stdout = None

return self.returncode

def kill(self):

os.kill(self.pid, signal.SIGKILL)

if self.stdin is not None:

self.stdin.close()

self.stdin = None

if self.stdout is not None:

self.stdout.close()

self.stdout = None

def call(*args):

cmd = []

if isinstance(args[0], str):

if len(args) == 1:

# splitting of arguments that cares about

# use of simple and double quotes

cmd = shlex.split(args[0])

else:

cmd = args

elif isinstance(args[0], list) and len(args) == 1:

cmd = args[0]

else:

raise Exception("Wrong arguments passed to subprocess.call")

pid = posix_spawn.posix_spawnp(cmd[0], cmd)

return os.waitpid(pid, 0)

if __name__ == '__main__':

# unit test

p = Popen(["tr", "abc", "def"], stdin=PIPE, stdout=PIPE)

p.stdin.write("blah")

p.stdin.close()

print(p.stdout.read())

p.wait()

p = Popen(["tr", "abc", "def"], stdin=PIPE, stdout=PIPE)

p.stdin.write("blah")

print(p.communicate())

call("echo blah0")

call(["echo", "blah1"])

call("echo", "blah2")