Question

I’m trying to make a program that does this:

1. Calls program 1 in a thread
2. Calls program 2 in another thread
3. If program 1 ends first, kill program 2, or vice-versa.

I’ve been trying for a long time and these are my current problem:

1. I can’t import Thread module (not threading!).
2. Function or Class, that is the question.

I already know how to call the processes using subprocess.Popen and how to kill them usign a command line function. I also know how to get the PID.

Here’s my actual code:

import threading, subprocess, shlex

class Prog1(threading.Thread):
    def __init__(self, arg=''):
        self.arg = arg
        threading.Thread.__init__(self)

    def run(self):
        p = subprocess.Popen(shelx.split(self.arg))
        global p.pid
        subprocess.Popen(shelx.split("kill -9 " + q.pid))


class Prog2(threading.Thread):
    def __init__(self, arg=''):
        self.arg = arg
        threading.Thread.__init__(self)

    def run(self):
        q = subprocess.Popen(shelx.split(self.arg))
        global q.pid
        subprocess.Popen(shelx.split("kill -9 " + p.pid))

Answer 1

To kill all processes if any of them has exited you could call process.wait() for each process in a separate thread and use threading.Event to signal if any of the processes ended:

#!/usr/bin/env python
import shlex
import subprocess
import threading


def kill_all(processes):
    for p in processes:
        try:
            if p.poll() is None:
                p.kill()  # note: it may leave orphans
                p.wait()
        except:  # pylint: disable=W0702
            pass  # ignore whatever it is (including SIGINT)


def wait(process, exit_event):
    try:
        process.wait()
    finally:
        exit_event.set()  # signal the process has exited


def main():
    # start processes
    cmd = "/bin/bash -c 'echo start {0}; sleep {0}; echo done {0}'".format
    processes = []
    for i in range(1, 3):
        try:
            processes.append(subprocess.Popen(shlex.split(cmd(i))))
        except EnvironmentError:
            kill_all(processes)  # failed to start some process; kill'em all
            return 1  # error

    # wait until at least one process finishes
    exit_event = threading.Event()
    for p in processes:
        threading.Thread(target=wait, args=(p, exit_event)).start()

    exit_event.wait()
    kill_all(processes)

if __name__ == "__main__":
    import sys
    sys.exit(main())

Output

start 1
start 2
done 1