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84f28db66a
os.name == "nt". This makes test_popen2 pass under Win98SE. HOWEVER, the Win98 "more" invents a leading newline out of thin air, and I'm not sure that the other Windows flavors of "more" also do that. So, somebody please try under other Windows flavors!
170 lines
5.7 KiB
Python
170 lines
5.7 KiB
Python
"""Spawn a command with pipes to its stdin, stdout, and optionally stderr.
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The normal os.popen(cmd, mode) call spawns a shell command and provides a
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file interface to just the input or output of the process depending on
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whether mode is 'r' or 'w'. This module provides the functions popen2(cmd)
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and popen3(cmd) which return two or three pipes to the spawned command.
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"""
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import os
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import sys
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import string
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MAXFD = 256 # Max number of file descriptors (os.getdtablesize()???)
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_active = []
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def _cleanup():
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for inst in _active[:]:
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inst.poll()
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class Popen3:
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"""Class representing a child process. Normally instances are created
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by the factory functions popen2() and popen3()."""
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def __init__(self, cmd, capturestderr=0, bufsize=-1):
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"""The parameter 'cmd' is the shell command to execute in a
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sub-process. The 'capturestderr' flag, if true, specifies that
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the object should capture standard error output of the child process.
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The default is false. If the 'bufsize' parameter is specified, it
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specifies the size of the I/O buffers to/from the child process."""
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if type(cmd) == type(''):
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cmd = ['/bin/sh', '-c', cmd]
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p2cread, p2cwrite = os.pipe()
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c2pread, c2pwrite = os.pipe()
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if capturestderr:
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errout, errin = os.pipe()
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self.pid = os.fork()
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if self.pid == 0:
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# Child
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os.close(0)
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os.close(1)
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if os.dup(p2cread) <> 0:
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sys.stderr.write('popen2: bad read dup\n')
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if os.dup(c2pwrite) <> 1:
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sys.stderr.write('popen2: bad write dup\n')
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if capturestderr:
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os.close(2)
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if os.dup(errin) <> 2: pass
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for i in range(3, MAXFD):
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try:
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os.close(i)
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except: pass
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try:
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os.execvp(cmd[0], cmd)
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finally:
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os._exit(1)
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# Shouldn't come here, I guess
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os._exit(1)
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os.close(p2cread)
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self.tochild = os.fdopen(p2cwrite, 'w', bufsize)
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os.close(c2pwrite)
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self.fromchild = os.fdopen(c2pread, 'r', bufsize)
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if capturestderr:
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os.close(errin)
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self.childerr = os.fdopen(errout, 'r', bufsize)
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else:
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self.childerr = None
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self.sts = -1 # Child not completed yet
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_active.append(self)
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def poll(self):
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"""Return the exit status of the child process if it has finished,
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or -1 if it hasn't finished yet."""
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if self.sts < 0:
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try:
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pid, sts = os.waitpid(self.pid, os.WNOHANG)
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if pid == self.pid:
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self.sts = sts
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_active.remove(self)
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except os.error:
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pass
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return self.sts
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def wait(self):
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"""Wait for and return the exit status of the child process."""
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pid, sts = os.waitpid(self.pid, 0)
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if pid == self.pid:
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self.sts = sts
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_active.remove(self)
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return self.sts
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if hasattr(os, "popen2"):
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def popen2(cmd, mode='t', bufsize=-1):
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"""Execute the shell command 'cmd' in a sub-process. If 'bufsize' is
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specified, it sets the buffer size for the I/O pipes. The file objects
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(child_stdout, child_stdin) are returned."""
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w, r = os.popen2(cmd, mode, bufsize)
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return r, w
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else:
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def popen2(cmd, mode='t', bufsize=-1):
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"""Execute the shell command 'cmd' in a sub-process. If 'bufsize' is
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specified, it sets the buffer size for the I/O pipes. The file objects
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(child_stdout, child_stdin) are returned."""
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if type(mode) is type(0) and bufsize == -1:
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bufsize = mode
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mode = 't'
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assert mode in ('t', 'b')
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_cleanup()
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inst = Popen3(cmd, 0, bufsize)
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return inst.fromchild, inst.tochild
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if hasattr(os, "popen3"):
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def popen3(cmd, mode='t', bufsize=-1):
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"""Execute the shell command 'cmd' in a sub-process. If 'bufsize' is
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specified, it sets the buffer size for the I/O pipes. The file objects
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(child_stdout, child_stdin, child_stderr) are returned."""
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w, r, e = os.popen3(cmd, mode, bufsize)
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return r, w, e
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else:
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def popen3(cmd, mode='t', bufsize=-1):
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"""Execute the shell command 'cmd' in a sub-process. If 'bufsize' is
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specified, it sets the buffer size for the I/O pipes. The file objects
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(child_stdout, child_stdin, child_stderr) are returned."""
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if type(mode) is type(0) and bufsize == -1:
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bufsize = mode
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mode = 't'
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assert mode in ('t', 'b')
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_cleanup()
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inst = Popen3(cmd, 1, bufsize)
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return inst.fromchild, inst.tochild, inst.childerr
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if hasattr(os, "popen4"):
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def popen4(cmd, mode='t', bufsize=-1):
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"""Execute the shell command 'cmd' in a sub-process. If 'bufsize' is
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specified, it sets the buffer size for the I/O pipes. The file objects
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(child_stdout_stderr, child_stdin) are returned."""
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w, r = os.popen4(cmd, mode, bufsize)
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return r, w
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else:
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pass # not yet on unix
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def _test():
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cmd = "cat"
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teststr = "abc\n"
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resultstr = teststr
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if os.name == "nt":
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cmd = "more"
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resultstr = "\n" + resultstr
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print "testing popen2..."
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r, w = popen2(cmd)
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w.write(teststr)
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w.close()
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assert r.read() == resultstr
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print "testing popen3..."
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try:
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r, w, e = popen3([cmd])
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except:
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r, w, e = popen3(cmd)
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w.write(teststr)
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w.close()
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assert r.read() == resultstr
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assert e.read() == ""
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for inst in _active[:]:
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inst.wait()
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assert not _active
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print "All OK"
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if __name__ == '__main__':
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_test()
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