title: Python's subprocess.Popen object hangs gathering child output when child process does not exit
body: <p>When a process exits abnormally or not at all, I still want to be able to gather what output it may have generated up until that point.</p>
  
  <p>The obvious solution to this example code is to kill the child process with an os.kill, but in my real code, the child is hung waiting for NFS and does not respond to a SIGKILL.</p>
  
  <pre><code>#!/usr/bin/python
  import subprocess
  import os
  import time
  import signal
  import sys
  child_script = """
  #!/bin/bash
  i=0
  while [ 1 ]; do
      echo "output line $i"
      i=$(expr $i \+ 1)
      sleep 1
  done
  """
  childFile = open("/tmp/childProc.sh", 'w')
  childFile.write(child_script)
  childFile.close()
  
  cmd = ["bash", "/tmp/childProc.sh"]
  finish = time.time() + 3
  p = subprocess.Popen(cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE, stdin=subprocess.PIPE)
  while p.poll() is None:
      time.sleep(0.05)
      if finish &lt; time.time():
          print "timed out and killed child, collecting what output exists so far"
          out, err = p.communicate()
          print "got it"
          sys.exit(0)
  </code></pre>
  
  <p>In this case, the print statement about timing out appears and the python script never exits or progresses. Does anybody know how I can do this differently and still get output from my child processe</p>