Lib/popen2.py

   1 import os
   2 import sys
   3 import string
   4
   5 MAXFD = 256     # Max number of file descriptors (os.getdtablesize()???)
   6
   7 _active = []
   8
   9 def _cleanup():
  10     for inst in _active[:]:
  11         inst.poll()
  12
  13 class Popen3:
  14     def __init__(self, cmd, capturestderr=0, bufsize=-1):
  15         if type(cmd) == type(''):
  16             cmd = ['/bin/sh', '-c', cmd]
  17         p2cread, p2cwrite = os.pipe()
  18         c2pread, c2pwrite = os.pipe()
  19         if capturestderr:
  20             errout, errin = os.pipe()
  21         self.pid = os.fork()
  22         if self.pid == 0:
  23             # Child
  24             os.close(0)
  25             os.close(1)
  26             if os.dup(p2cread) <> 0:
  27                 sys.stderr.write('popen2: bad read dup\n')
  28             if os.dup(c2pwrite) <> 1:
  29                 sys.stderr.write('popen2: bad write dup\n')
  30             if capturestderr:
  31                 os.close(2)
  32                 if os.dup(errin) <> 2: pass
  33             for i in range(3, MAXFD):
  34                 try:
  35                     os.close(i)
  36                 except: pass
  37             try:
  38                 os.execvp(cmd[0], cmd)
  39             finally:
  40                 os._exit(1)
  41             # Shouldn't come here, I guess
  42             os._exit(1)
  43         os.close(p2cread)
  44         self.tochild = os.fdopen(p2cwrite, 'w', bufsize)
  45         os.close(c2pwrite)
  46         self.fromchild = os.fdopen(c2pread, 'r', bufsize)
  47         if capturestderr:
  48             os.close(errin)
  49             self.childerr = os.fdopen(errout, 'r', bufsize)
  50         else:
  51             self.childerr = None
  52         self.sts = -1 # Child not completed yet
  53         _active.append(self)
  54     def poll(self):
  55         if self.sts < 0:
  56             try:
  57                 pid, sts = os.waitpid(self.pid, os.WNOHANG)
  58                 if pid == self.pid:
  59                     self.sts = sts
  60                     _active.remove(self)
  61             except os.error:
  62                 pass
  63         return self.sts
  64     def wait(self):
  65         pid, sts = os.waitpid(self.pid, 0)
  66         if pid == self.pid:
  67             self.sts = sts
  68             _active.remove(self)
  69         return self.sts
  70
  71 def popen2(cmd, bufsize=-1):
  72     _cleanup()
  73     inst = Popen3(cmd, 0, bufsize)
  74     return inst.fromchild, inst.tochild
  75
  76 def popen3(cmd, bufsize=-1):
  77     _cleanup()
  78     inst = Popen3(cmd, 1, bufsize)
  79     return inst.fromchild, inst.tochild, inst.childerr
  80
  81 def _test():
  82     teststr = "abc\n"
  83     print "testing popen2..."
  84     r, w = popen2('cat')
  85     w.write(teststr)
  86     w.close()
  87     assert r.read() == teststr
  88     print "testing popen3..."
  89     r, w, e = popen3(['cat'])
  90     w.write(teststr)
  91     w.close()
  92     assert r.read() == teststr
  93     assert e.read() == ""
  94     _cleanup()
  95     assert not _active
  96     print "All OK"
  97
  98 if __name__ == '__main__':
  99     _test()