Speno's Pythonic Avocado 4.2.2004

Popen5: useful!

I've been playing with Peter Astrand's Popen5 module lately. It's really nice and I hope that it will be accepted into Python's standard library eventually via PEP 324 .

I like this module because it allows nice and easy control over child processes. I get full control of the child's stdin, stdout, and stderr without having to do the dup dance (which I'd always have to lookup before this). And I can make an easy timeout without having to use SIGALRM.

I especially appreciate Popen5 in light of having spent way too much time tring to get a simple return value out of Twisted's utils.getProcessValue() last weekend. But that was mostly my fault.

Here's an example of using Popen5:

import popen5
import time
import os
import signal

def main():

    wait_time = 5 # seconds
    args = ['/sbin/ping', '-i', '10', 'localhost']

    outf = open('ping.out', 'w+')
    errf = open('ping.err', 'w+')

    ping = popen5.Popen(args, stdout=outf, stderr=errf)

    print 'ping started with pid ', ping.pid

    time_done = time.time() + wait_time

    while ping.poll() == -1:
        if time.time() > time_done:
            print 'bored now!'
            os.kill(ping.pid, signal.SIGINT)
            time.sleep(1)
            os.waitpid(ping.pid, os.WNOHANG)
            break
        else:
            time.sleep(1)

    for f in [outf, errf]:
        f.seek(0)
        output = f.read()
        if output:
            print 'Contents of %s:' % f.name
            print output
        
if __name__ == '__main__':
    main()

Take care.

P.S. Thanks to everyone who's left comments here. I'm learning a lot, and feel more like a member of the global Python community now. Since I won't make it to either PyCon or OSCON this year, I'm glad I have this.