Python subprocess timeout?

Question

Is there any argument or options to setup a timeout for Python\'s subprocess.Popen method?

Something like this:

subprocess.Popen([\'..\'], ..., timeout

Answer 1

import subprocess, threading

class Command(object):
    def __init__(self, cmd):
        self.cmd = cmd
        self.process = None

    def run(self, timeout):
        def target():
            print 'Thread started'
            self.process = subprocess.Popen(self.cmd, shell=True)
            self.process.communicate()
            print 'Thread finished'

        thread = threading.Thread(target=target)
        thread.start()

        thread.join(timeout)
        if thread.is_alive():
            print 'Terminating process'
            self.process.terminate()
            thread.join()
        print self.process.returncode

command = Command("echo 'Process started'; sleep 2; echo 'Process finished'")
command.run(timeout=3)
command.run(timeout=1)

The output of this should be:

Thread started
Process started
Process finished
Thread finished
0
Thread started
Process started
Terminating process
Thread finished
-15

where it can be seen that, in the first execution, the process finished correctly (return code 0), while the in the second one the process was terminated (return code -15).

I haven't tested in windows; but, aside from updating the example command, I think it should work since I haven't found in the documentation anything that says that thread.join or process.terminate is not supported.

Answer 2

Unfortunately, there isn't such a solution. I managed to do this using a threaded timer that would launch along with the process that would kill it after the timeout but I did run into some stale file descriptor issues because of zombie processes or some such.

Answer 3

As of Python 3.3, there is also a timeout argument to the blocking helper functions in the subprocess module.

https://docs.python.org/3/library/subprocess.html

Answer 4

subprocess.Popen doesn't block so you can do something like this:

import time

p = subprocess.Popen(['...'])
time.sleep(20)
if p.poll() is None:
  p.kill()
  print 'timed out'
else:
  print p.communicate()

It has a drawback in that you must always wait at least 20 seconds for it to finish.