obtaining pid of child process

Question

I am using python's multiprocessing module to spawn new process

as follows :

import multiprocessing
import os
d = multiprocessing.Process(target=os.system,args=('iostat 2 > a.txt',))
d.start()

I want to obtain pid of iostat command or the command executed using multiprocessing module

When I execute :

 d.pid 

it gives me pid of subshell in which this command is running .

Any help will be valuable .

Thanks in advance

Answer 1

Similar to @rakslice, you can use psutil:

import signal, psutil
def kill_child_processes(parent_pid, sig=signal.SIGTERM):
    try:
      parent = psutil.Process(parent_pid)
    except psutil.NoSuchProcess:
      return
    children = parent.children(recursive=True)
    for process in children:
      process.send_signal(sig)

Answer 2

Since you appear to be using Unix, you can use a quick ps command to get the details of the child processes, like I did here (this is Linux-specific):

import subprocess, os, signal

def kill_child_processes(parent_pid, sig=signal.SIGTERM):
        ps_command = subprocess.Popen("ps -o pid --ppid %d --noheaders" % parent_pid, shell=True, stdout=subprocess.PIPE)
        ps_output = ps_command.stdout.read()
        retcode = ps_command.wait()
        assert retcode == 0, "ps command returned %d" % retcode
        for pid_str in ps_output.split("\n")[:-1]:
                os.kill(int(pid_str), sig)