| 1 | """Spawn a command with pipes to its stdin, stdout, and optionally stderr.
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| 2 |
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| 3 | The normal os.popen(cmd, mode) call spawns a shell command and provides a
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| 4 | file interface to just the input or output of the process depending on
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| 5 | whether mode is 'r' or 'w'. This module provides the functions popen2(cmd)
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| 6 | and popen3(cmd) which return two or three pipes to the spawned command.
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| 7 | """
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| 8 |
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| 9 | import os
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| 10 | import sys
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| 11 |
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| 12 | __all__ = ["popen2", "popen3", "popen4"]
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| 13 |
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| 14 | try:
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| 15 | MAXFD = os.sysconf('SC_OPEN_MAX')
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| 16 | except (AttributeError, ValueError):
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| 17 | MAXFD = 256
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| 18 |
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| 19 | _active = []
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| 20 |
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| 21 | def _cleanup():
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| 22 | for inst in _active[:]:
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| 23 | if inst.poll(_deadstate=sys.maxint) >= 0:
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| 24 | try:
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| 25 | _active.remove(inst)
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| 26 | except ValueError:
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| 27 | # This can happen if two threads create a new Popen instance.
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| 28 | # It's harmless that it was already removed, so ignore.
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| 29 | pass
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| 30 |
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| 31 | class Popen3:
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| 32 | """Class representing a child process. Normally instances are created
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| 33 | by the factory functions popen2() and popen3()."""
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| 34 |
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| 35 | sts = -1 # Child not completed yet
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| 36 |
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| 37 | def __init__(self, cmd, capturestderr=False, bufsize=-1):
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| 38 | """The parameter 'cmd' is the shell command to execute in a
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| 39 | sub-process. On UNIX, 'cmd' may be a sequence, in which case arguments
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| 40 | will be passed directly to the program without shell intervention (as
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| 41 | with os.spawnv()). If 'cmd' is a string it will be passed to the shell
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| 42 | (as with os.system()). The 'capturestderr' flag, if true, specifies
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| 43 | that the object should capture standard error output of the child
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| 44 | process. The default is false. If the 'bufsize' parameter is
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| 45 | specified, it specifies the size of the I/O buffers to/from the child
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| 46 | process."""
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| 47 | _cleanup()
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| 48 | self.cmd = cmd
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| 49 | p2cread, p2cwrite = os.pipe()
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| 50 | c2pread, c2pwrite = os.pipe()
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| 51 | if capturestderr:
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| 52 | errout, errin = os.pipe()
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| 53 | self.pid = os.fork()
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| 54 | if self.pid == 0:
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| 55 | # Child
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| 56 | os.dup2(p2cread, 0)
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| 57 | os.dup2(c2pwrite, 1)
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| 58 | if capturestderr:
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| 59 | os.dup2(errin, 2)
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| 60 | self._run_child(cmd)
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| 61 | os.close(p2cread)
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| 62 | self.tochild = os.fdopen(p2cwrite, 'w', bufsize)
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| 63 | os.close(c2pwrite)
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| 64 | self.fromchild = os.fdopen(c2pread, 'r', bufsize)
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| 65 | if capturestderr:
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| 66 | os.close(errin)
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| 67 | self.childerr = os.fdopen(errout, 'r', bufsize)
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| 68 | else:
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| 69 | self.childerr = None
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| 70 |
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| 71 | def __del__(self):
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| 72 | # In case the child hasn't been waited on, check if it's done.
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| 73 | self.poll(_deadstate=sys.maxint)
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| 74 | if self.sts < 0:
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| 75 | if _active is not None:
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| 76 | # Child is still running, keep us alive until we can wait on it.
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| 77 | _active.append(self)
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| 78 |
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| 79 | def _run_child(self, cmd):
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| 80 | if isinstance(cmd, basestring):
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| 81 | cmd = ['/bin/sh', '-c', cmd]
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| 82 | for i in xrange(3, MAXFD):
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| 83 | try:
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| 84 | os.close(i)
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| 85 | except OSError:
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| 86 | pass
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| 87 | try:
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| 88 | os.execvp(cmd[0], cmd)
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| 89 | finally:
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| 90 | os._exit(1)
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| 91 |
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| 92 | def poll(self, _deadstate=None):
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| 93 | """Return the exit status of the child process if it has finished,
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| 94 | or -1 if it hasn't finished yet."""
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| 95 | if self.sts < 0:
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| 96 | try:
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| 97 | pid, sts = os.waitpid(self.pid, os.WNOHANG)
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| 98 | # pid will be 0 if self.pid hasn't terminated
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| 99 | if pid == self.pid:
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| 100 | self.sts = sts
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| 101 | except os.error:
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| 102 | if _deadstate is not None:
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| 103 | self.sts = _deadstate
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| 104 | return self.sts
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| 105 |
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| 106 | def wait(self):
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| 107 | """Wait for and return the exit status of the child process."""
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| 108 | if self.sts < 0:
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| 109 | pid, sts = os.waitpid(self.pid, 0)
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| 110 | # This used to be a test, but it is believed to be
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| 111 | # always true, so I changed it to an assertion - mvl
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| 112 | assert pid == self.pid
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| 113 | self.sts = sts
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| 114 | return self.sts
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| 115 |
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| 116 |
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| 117 | class Popen4(Popen3):
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| 118 | childerr = None
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| 119 |
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| 120 | def __init__(self, cmd, bufsize=-1):
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| 121 | _cleanup()
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| 122 | self.cmd = cmd
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| 123 | p2cread, p2cwrite = os.pipe()
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| 124 | c2pread, c2pwrite = os.pipe()
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| 125 | self.pid = os.fork()
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| 126 | if self.pid == 0:
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| 127 | # Child
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| 128 | os.dup2(p2cread, 0)
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| 129 | os.dup2(c2pwrite, 1)
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| 130 | os.dup2(c2pwrite, 2)
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| 131 | self._run_child(cmd)
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| 132 | os.close(p2cread)
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| 133 | self.tochild = os.fdopen(p2cwrite, 'w', bufsize)
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| 134 | os.close(c2pwrite)
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| 135 | self.fromchild = os.fdopen(c2pread, 'r', bufsize)
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| 136 |
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| 137 |
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| 138 | if sys.platform[:3] == "win" or sys.platform == "os2emx":
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| 139 | # Some things don't make sense on non-Unix platforms.
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| 140 | del Popen3, Popen4
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| 141 |
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| 142 | def popen2(cmd, bufsize=-1, mode='t'):
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| 143 | """Execute the shell command 'cmd' in a sub-process. On UNIX, 'cmd' may
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| 144 | be a sequence, in which case arguments will be passed directly to the
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| 145 | program without shell intervention (as with os.spawnv()). If 'cmd' is a
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| 146 | string it will be passed to the shell (as with os.system()). If
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| 147 | 'bufsize' is specified, it sets the buffer size for the I/O pipes. The
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| 148 | file objects (child_stdout, child_stdin) are returned."""
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| 149 | w, r = os.popen2(cmd, mode, bufsize)
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| 150 | return r, w
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| 151 |
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| 152 | def popen3(cmd, bufsize=-1, mode='t'):
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| 153 | """Execute the shell command 'cmd' in a sub-process. On UNIX, 'cmd' may
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| 154 | be a sequence, in which case arguments will be passed directly to the
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| 155 | program without shell intervention (as with os.spawnv()). If 'cmd' is a
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| 156 | string it will be passed to the shell (as with os.system()). If
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| 157 | 'bufsize' is specified, it sets the buffer size for the I/O pipes. The
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| 158 | file objects (child_stdout, child_stdin, child_stderr) are returned."""
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| 159 | w, r, e = os.popen3(cmd, mode, bufsize)
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| 160 | return r, w, e
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| 161 |
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| 162 | def popen4(cmd, bufsize=-1, mode='t'):
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| 163 | """Execute the shell command 'cmd' in a sub-process. On UNIX, 'cmd' may
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| 164 | be a sequence, in which case arguments will be passed directly to the
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| 165 | program without shell intervention (as with os.spawnv()). If 'cmd' is a
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| 166 | string it will be passed to the shell (as with os.system()). If
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| 167 | 'bufsize' is specified, it sets the buffer size for the I/O pipes. The
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| 168 | file objects (child_stdout_stderr, child_stdin) are returned."""
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| 169 | w, r = os.popen4(cmd, mode, bufsize)
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| 170 | return r, w
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| 171 | else:
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| 172 | def popen2(cmd, bufsize=-1, mode='t'):
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| 173 | """Execute the shell command 'cmd' in a sub-process. On UNIX, 'cmd' may
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| 174 | be a sequence, in which case arguments will be passed directly to the
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| 175 | program without shell intervention (as with os.spawnv()). If 'cmd' is a
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| 176 | string it will be passed to the shell (as with os.system()). If
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| 177 | 'bufsize' is specified, it sets the buffer size for the I/O pipes. The
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| 178 | file objects (child_stdout, child_stdin) are returned."""
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| 179 | inst = Popen3(cmd, False, bufsize)
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| 180 | return inst.fromchild, inst.tochild
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| 181 |
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| 182 | def popen3(cmd, bufsize=-1, mode='t'):
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| 183 | """Execute the shell command 'cmd' in a sub-process. On UNIX, 'cmd' may
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| 184 | be a sequence, in which case arguments will be passed directly to the
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| 185 | program without shell intervention (as with os.spawnv()). If 'cmd' is a
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| 186 | string it will be passed to the shell (as with os.system()). If
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| 187 | 'bufsize' is specified, it sets the buffer size for the I/O pipes. The
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| 188 | file objects (child_stdout, child_stdin, child_stderr) are returned."""
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| 189 | inst = Popen3(cmd, True, bufsize)
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| 190 | return inst.fromchild, inst.tochild, inst.childerr
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| 191 |
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| 192 | def popen4(cmd, bufsize=-1, mode='t'):
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| 193 | """Execute the shell command 'cmd' in a sub-process. On UNIX, 'cmd' may
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| 194 | be a sequence, in which case arguments will be passed directly to the
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| 195 | program without shell intervention (as with os.spawnv()). If 'cmd' is a
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