How to kill a python child process created with subprocess.check_output() when the parent dies?

Question

I am running on a linux machine a python script which creates a child process using subprocess.check_output() as it follows:

subprocess.check_output([\"ls\",         


        

Answer 1

Yes, you can achieve this by two methods. Both of them require you to use Popen instead of check_output. The first is a simpler method, using try..finally, as follows:

from contextlib import contextmanager

@contextmanager
def run_and_terminate_process(*args, **kwargs):
try:
    p = subprocess.Popen(*args, **kwargs)
    yield p        
finally:
    p.terminate() # send sigterm, or ...
    p.kill()      # send sigkill

def main():
    with run_and_terminate_process(args) as running_proc:
        # Your code here, such as running_proc.stdout.readline()

This will catch sigint (keyboard interrupt) and sigterm, but not sigkill (if you kill your script with -9).

The other method is a bit more complex, and uses ctypes' prctl PR_SET_PDEATHSIG. The system will send a signal to the child once the parent exits for any reason (even sigkill).

import signal
import ctypes
libc = ctypes.CDLL("libc.so.6")
def set_pdeathsig(sig = signal.SIGTERM):
    def callable():
        return libc.prctl(1, sig)
    return callable
p = subprocess.Popen(args, preexec_fn = set_pdeathsig(signal.SIGTERM))