subprocess - ping for indefinite amount of time and get its output in Python

Question

The task is: Try to send ping in python using the most basic form like "ping 8.8.8.8". After some time terminate the ping command (In a terminal, one will do Ctrl+C) and get its output. The last several lines of output which shows the ping statistics are of particular interest.

Two methods tried, did not work. My OS version is Mac OS X 10.10.1.

First method uses module pexpect, and ping will stop after about 17 seconds though I did not ask it to stop:

import pexpect
import time
child = pexpect.spawn('ping 8.8.8.8')
(x, y) = child.getwinsize()
print x
print y
time.sleep(21)
child.terminate()
x = child.read()
print x

Second Method uses module subprocess, and the last several lines of ping output are lost:

import time
from subprocess import PIPE, Popen
child = Popen(['ping', '8.8.8.8'], stdin = PIPE, stdout = PIPE, stderr = PIPE)
time.sleep(5)
child.terminate()
x = child.stdout.read()
print x
x = child.stderr.read()
print x

I'd appreciate any help! "ping -c XXX" is not accepted.

Answer 1

ping will block in your code as soon as it fills its stdout OS pipe buffer (~65K on my system). You need to read the output:

#!/usr/bin/env python
import signal
from subprocess import Popen, PIPE
from threading import Timer

child = Popen(['ping', '8.8.8.8'], stdin=PIPE, stdout=PIPE, stderr=PIPE)
Timer(5, child.send_signal, [signal.SIGINT]).start() # Ctrl+C in 5 seconds
out, err = child.communicate() # get output
print(out.decode())
print('*'*60)
print(err.decode())