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popen2.py
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"""Spawn a command with pipes to its stdin, stdout, and optionally stderr. The normal os.popen(cmd, mode) call spawns a shell command and provides a file interface to just the input or output of the process depending on whether mode is 'r' or 'w'. This module provides the functions popen2(cmd) and popen3(cmd) which return two or three pipes to the spawned command. """ import os import sys import warnings warnings.warn("The popen2 module is deprecated. Use the subprocess module.", DeprecationWarning, stacklevel=2) __all__ = ["popen2", "popen3", "popen4"] try: MAXFD = os.sysconf('SC_OPEN_MAX') except (AttributeError, ValueError): MAXFD = 256 _active = [] def _cleanup(): for inst in _active[:]: if inst.poll(_deadstate=sys.maxint) >= 0: try: _active.remove(inst) except ValueError: # This can happen if two threads create a new Popen instance. # It's harmless that it was already removed, so ignore. pass class Popen3: """Class representing a child process. Normally, instances are created internally by the functions popen2() and popen3().""" sts = -1 # Child not completed yet def __init__(self, cmd, capturestderr=False, bufsize=-1): """The parameter 'cmd' is the shell command to execute in a sub-process. On UNIX, 'cmd' may be a sequence, in which case arguments will be passed directly to the program without shell intervention (as with os.spawnv()). If 'cmd' is a string it will be passed to the shell (as with os.system()). The 'capturestderr' flag, if true, specifies that the object should capture standard error output of the child process. The default is false. If the 'bufsize' parameter is specified, it specifies the size of the I/O buffers to/from the child process.""" _cleanup() self.cmd = cmd p2cread, p2cwrite = os.pipe() c2pread, c2pwrite = os.pipe() if capturestderr: errout, errin = os.pipe() self.pid = os.fork() if self.pid == 0: # Child os.dup2(p2cread, 0) os.dup2(c2pwrite, 1) if capturestderr: os.dup2(errin, 2) self._run_child(cmd) os.close(p2cread) self.tochild = os.fdopen(p2cwrite, 'w', bufsize) os.close(c2pwrite) self.fromchild = os.fdopen(c2pread, 'r', bufsize) if capturestderr: os.close(errin) self.childerr = os.fdopen(errout, 'r', bufsize) else: self.childerr = None def __del__(self): # In case the child hasn't been waited on, check if it's done. self.poll(_deadstate=sys.maxint) if self.sts < 0: if _active is not None: # Child is still running, keep us alive until we can wait on it. _active.append(self) def _run_child(self, cmd): if isinstance(cmd, basestring): cmd = ['/bin/sh', '-c', cmd] os.closerange(3, MAXFD) try: os.execvp(cmd[0], cmd) finally: os._exit(1) def poll(self, _deadstate=None): """Return the exit status of the child process if it has finished, or -1 if it hasn't finished yet.""" if self.sts < 0: try: pid, sts = os.waitpid(self.pid, os.WNOHANG) # pid will be 0 if self.pid hasn't terminated if pid == self.pid: self.sts = sts except os.error: if _deadstate is not None: self.sts = _deadstate return self.sts def wait(self): """Wait for and return the exit status of the child process.""" if self.sts < 0: pid, sts = os.waitpid(self.pid, 0) # This used to be a test, but it is believed to be # always true, so I changed it to an assertion - mvl assert pid == self.pid self.sts = sts return self.sts class Popen4(Popen3): childerr = None def __init__(self, cmd, bufsize=-1): _cleanup() self.cmd = cmd p2cread, p2cwrite = os.pipe() c2pread, c2pwrite = os.pipe() self.pid = os.fork() if self.pid == 0: # Child os.dup2(p2cread, 0) os.dup2(c2pwrite, 1) os.dup2(c2pwrite, 2) self._run_child(cmd) os.close(p2cread) self.tochild = os.fdopen(p2cwrite, 'w', bufsize) os.close(c2pwrite) self.fromchild = os.fdopen(c2pread, 'r', bufsize) if sys.platform[:3] == "win" or sys.platform == "os2emx": # Some things don't make sense on non-Unix platforms. del Popen3, Popen4 def popen2(cmd, bufsize=-1, mode='t'): """Execute the shell command 'cmd' in a sub-process. On UNIX, 'cmd' may be a sequence, in which case arguments will be passed directly to the program without shell intervention (as with os.spawnv()). If 'cmd' is a string it will be passed to the shell (as with os.system()). If 'bufsize' is specified, it sets the buffer size for the I/O pipes. The file objects (child_stdout, child_stdin) are returned.""" w, r = os.popen2(cmd, mode, bufsize) return r, w def popen3(cmd, bufsize=-1, mode='t'): """Execute the shell command 'cmd' in a sub-process. On UNIX, 'cmd' may be a sequence, in which case arguments will be passed directly to the program without shell intervention (as with os.spawnv()). If 'cmd' is a string it will be passed to the shell (as with os.system()). If 'bufsize' is specified, it sets the buffer size for the I/O pipes. The file objects (child_stdout, child_stdin, child_stderr) are returned.""" w, r, e = os.popen3(cmd, mode, bufsize) return r, w, e def popen4(cmd, bufsize=-1, mode='t'): """Execute the shell command 'cmd' in a sub-process. On UNIX, 'cmd' may be a sequence, in which case arguments will be passed directly to the program without shell intervention (as with os.spawnv()). If 'cmd' is a string it will be passed to the shell (as with os.system()). If 'bufsize' is specified, it sets the buffer size for the I/O pipes. The file objects (child_stdout_stderr, child_stdin) are returned.""" w, r = os.popen4(cmd, mode, bufsize) return r, w else: def popen2(cmd, bufsize=-1, mode='t'): """Execute the shell command 'cmd' in a sub-process. On UNIX, 'cmd' may be a sequence, in which case arguments will be passed directly to the program without shell intervention (as with os.spawnv()). If 'cmd' is a string it will be passed to the shell (as with os.system()). If 'bufsize' is specified, it sets the buffer size for the I/O pipes. The file objects (child_stdout, child_stdin) are returned.""" inst = Popen3(cmd, False, bufsize) return inst.fromchild, inst.tochild def popen3(cmd, bufsize=-1, mode='t'): """Execute the shell command 'cmd' in a sub-process. On UNIX, 'cmd' may be a sequence, in which case arguments will be passed directly to the program without shell intervention (as with os.spawnv()). If 'cmd' is a string it will be passed to the shell (as with os.system()). If 'bufsize' is specified, it sets the buffer size for the I/O pipes. The file objects (child_stdout, child_stdin, child_stderr) are returned.""" inst = Popen3(cmd, True, bufsize) return inst.fromchild, inst.tochild, inst.childerr def popen4(cmd, bufsize=-1, mode='t'): """Execute the shell command 'cmd' in a sub-process. On UNIX, 'cmd' may be a sequence, in which case arguments will be passed directly to the program without shell intervention (as with os.spawnv()). If 'cmd' is a string it will be passed to the shell (as with os.system()). If 'bufsize' is specified, it sets the buffer size for the I/O pipes. The file objects (child_stdout_stderr, child_stdin) are returned.""" inst = Popen4(cmd, bufsize) return inst.fromchild, inst.tochild __all__.extend(["Popen3", "Popen4"])