Zombie process test

testprocess.py

#!/usr/bin/env python3 -u
# This shell script simulates a CGI web server.
# Save as 'testprocess.py' and run with:
# docker run -i --rm ubuntu:14.04 python3 -u < testprocess.py
import os, signal, time

# The web server spawns a CGI script, which in turn spawns a long-running 'grep',
# simulated here by 'sleep 999'.
print("Spawning CGI script")
pid = os.fork()
if pid == 0:
	# Child
	os.setpgrp()
	os.execlp("bash", "bash", "-c", "set -e && sleep 999")
print("CGI script running as PID %d" % pid)

time.sleep(1)
print()
print("Current processes:")
os.system("ps aux")

print()
print("Terminating CGI script")
os.killpg(pid, signal.SIGTERM)
os.waitpid(pid, 0)

time.sleep(1)
print()
print("Current processes:")
os.system("ps aux")

print()
print("See the [sleep] <defunct> there? That's a zombie process.")