1

#!/usr/bin/env python

     2

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

     3

     4

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

     5

     7

import os

     8

import signal

    10

    11

PIPE = "42"

    12

    14

class Popen(object):

    16

        self.returncode = None

    17

        self.stdout = None

    18

        self.stdin = None

    19

        # TODO: stderr

    20

        file_actions = posix_spawn.FileActions()

    21

        if stdout is not None:

    22

            # child's stdout, child 2 parent pipe

    23

            c2pread, c2pwrite = os.pipe()

    24

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

    25

            file_actions.add_dup2(c2pwrite, 1)

    26

            # close other end

    27

            file_actions.add_close(c2pread)

    28

        if stdin is not None:

    29

            # child's stdin, parent to child pipe

    30

            p2cread, p2cwrite = os.pipe()

    31

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

    32

            file_actions.add_dup2(p2cread, 0)

    33

            # close other end

    34

            file_actions.add_close(p2cwrite)

    35

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

    36

        if stdout is not None:

    37

            self.stdout = os.fdopen(c2pread)

    38

            os.close(c2pwrite)

    39

        if stdin is not None:

    40

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

    41

            os.close(p2cread)

    42

    43

    def _wait(self):

    44

        if self.returncode is None:

    46

    47

    def communicate(self):

    48

        if self.stdin is not None:

    49

            self.stdin.close()

    50

            self.stdin = None

    51

        if self.stdout is not None:

    52

            stdoutdata = self.stdout.read()

    53

        else:

    54

            stdoutdata = ""

    56

        # TODO

    57

        stderrdata = ""

    58

    59

        self._wait()

    60

        if self.stdout is not None:

    61

            self.stdout.close()

    62

            self.stdout = None

    64

        return (stdoutdata, stderrdata)

    65

    66

    def wait(self):

    67

        if self.stdin is not None:

    68

            self.stdin.close()

    69

            self.stdin = None

    70

        self._wait()

    71

        if self.stdout is not None:

    72

            self.stdout.close()

    73

            self.stdout = None

    74

        return self.returncode

    75

    76

    def poll(self):

    77

        if self.returncode is None:

    78

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

    80

                self.returncode = ret

    81

    82

                if self.stdin is not None:

    83

                    self.stdin.close()

    84

                    self.stdin = None

    85

                if self.stdout is not None:

    86

                    self.stdout.close()

    87

                    self.stdout = None

    88

    89

        return self.returncode

    91

    def kill(self):

    92

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

    93

    94

        if self.stdin is not None:

    95

            self.stdin.close()

    96

            self.stdin = None

    97

        if self.stdout is not None:

    98

            self.stdout.close()

    99

            self.stdout = None

   100

   101

   102

def call(*args):

   103

    cmd = []

   104

    if isinstance(args[0], str):

   106

            # oversimplified splitting of arguments,

   107

            # TODO: care about use of simple and double quotes

   108

            cmd = args[0].split()

   109

        else:

   110

            cmd = args

   112

        cmd = args[0]

   113

    else:

   114

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

   115

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

   118

   119

if __name__ == '__main__':

   120

    # unit test

   121

   122

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

   123

    p.stdin.write("blah")

   124

    p.stdin.close()

   126

    p.wait()

   127

   128

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

   129

    p.stdin.write("blah")

   131

   132

    call("echo blah0")

   133

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

   134

    call("echo", "blah2")