Question

I have a process that is started via subprocess.Popen() which is meant to run indefinitely. The problem i was having was that the process seemed to stop running after about 20 seconds. Sure enough when i check top, it shows that the process is going to sleep. When i run the command manually this doesn’t happen.

Anyone know how I can stop this from happening?

This is the subprocess call:

aireplay = subprocess.Popen('aireplay-ng -3 -b ' + target.mac + ' ' + interface, 
                            shell=True, stdout = subprocess.PIPE, stderr = DN)

time.sleep(5)
starttime = time.time()
ivs = 0
second = False
print 'Sending deauth to generate arps...'
send_deauth(target)

while time.time() - starttime < 1200:
    targets = parsecsvfile('crackattempt')
    print 'Captured ' + str(ivs) + ' ivs.'
    print aireplay.poll()
    if len(targets[0]) > 0:
        target = targets[0][0]
        if ivs > 20000:
            break
        else :
            ivs = int(target.ivs)

    time.sleep(1)

Answer 1

You are piping the output of the subprocess. It will sleep when its buffer is full – did you remember to read stdout from the subprocess?

You could use the communicate method if you don’t mind it blocking, or read from the stdout file descriptor, or maybe send the stdout to /dev/null since you don’t seem to be using it.