make-zombies-using-wait.py

#!/usr/bin/env python
"""Make zombies using `.wait()`.

http://stackoverflow.com/questions/2760652
"""
import os
from threading import Timer
from subprocess import Popen

n = 10
many_seconds = 10

def check_zombies(expected_nzombies):
    #NOTE: don't use Popen() here
    output = os.popen(r"ps aux | grep Z | grep -v grep").read()
    print(output)
    got_nzombies = len(output.splitlines()) - 1
    assert expected_nzombies == got_nzombies


check_zombies(0) # no zombies

processes = [Popen("sleep %d" % many_seconds, shell=True)]
processes.extend(Popen("sleep 1", shell=True) for _ in range(n))

Timer(2, check_zombies, [n]).start() # should see zombies in 2 seconds
for p in processes:
    p.wait()

check_zombies(0)