之前发过一个类似的http://www.redicecn.com/html/Python/20120906/434.html，但是仅支持Windows平台，在Linux下命令超时后进程杀不死。

下面的方法能够同时支持Windows和Linux平台：

import os
import platform
import subprocess
import signal
import time

class TimeoutError(Exception):
    pass

def command(cmd, timeout=60):
    """Run command and return the output
    cmd - the command to run
    timeout - max seconds to wait for
    """
    is_linux = platform.system() == 'Linux'
    
    p = subprocess.Popen(cmd, stderr=subprocess.STDOUT, stdout=subprocess.PIPE, shell=True, preexec_fn=os.setsid if is_linux else None)
    t_beginning = time.time()
    seconds_passed = 0
    while True:
        if p.poll() is not None:
            break
        seconds_passed = time.time() - t_beginning
        if timeout and seconds_passed > timeout:
            if is_linux:
                os.killpg(p.pid, signal.SIGTERM)
            else:
                p.terminate()
            raise TimeoutError(cmd, timeout)
        time.sleep(0.1)
    return p.stdout.read()

if __name__ == '__main__':
    try:
        result = command('ping www.site-digger.com', timeout=10)
    except TimeoutError:
        print 'Run command timeout.'
    else:
        print result