cpython/Lib/popen2.py

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import os
import sys
import string
MAXFD = 100 # Max number of file descriptors (os.getdtablesize()???)
def _popen2(cmd, capturestderr=0):
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cmd = ['/bin/sh', '-c', cmd]
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p2cread, p2cwrite = os.pipe()
c2pread, c2pwrite = os.pipe()
if capturestderr:
errout, errin = os.pipe()
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pid = os.fork()
if pid == 0:
# Child
os.close(0)
os.close(1)
if os.dup(p2cread) <> 0:
sys.stderr.write('popen2: bad read dup\n')
if os.dup(c2pwrite) <> 1:
sys.stderr.write('popen2: bad write dup\n')
if capturestderr:
os.close(2)
if os.dup(errin) <> 2: pass
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for i in range(3, MAXFD):
try:
os.close(i)
except: pass
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try:
os.execv(cmd[0], cmd)
finally:
os._exit(1)
# Shouldn't come here, I guess
os._exit(1)
os.close(p2cread)
tochild = os.fdopen(p2cwrite, 'w')
os.close(c2pwrite)
fromchild = os.fdopen(c2pread, 'r')
if capturestderr:
os.close(errin)
childerr = os.fdopen(errout, 'r')
return fromchild, tochild, childerr
else:
return fromchild, tochild, None
def popen2(cmd):
return _popen2(cmd, 0)[:2]
def popen3(cmd):
return _popen2(cmd, 1)