import threading
import time
import os
import atexit
import signal

def run(label):
    for i in range(1, 10):
        sl = .5
        print("IN THREAD:", label, ", elapsed:", str(i*sl))
        time.sleep(sl)

def start(procName):
    tl = []
    for j in range(1,5):
        label = procName + ", thread# " + str(j)
        t = threading.Thread(target=run, args=(label,))
        t.daemon = False
        t.start()
        tl.append(t)
    return tl

def join(tl):
    for t in tl:
        t.join()

def runFork():
    pid = os.fork()
    if pid:
        print("PARENT FORKING THREAD", "IS" if threading.currentThread().daemon == True else "IS NOT", "DAEMON!")
        tl = start("Parent, pid: " + str(os.getpid()))
        os.waitpid(pid, 0)
    else:
        print("CHILD MAIN THREAD", "IS" if threading.currentThread().daemon == True else "IS NOT", "DAEMON!")
        tl = start("Child, pid: " + str(os.getpid()))
        t = threading.Thread(target=lambda: time.sleep(3600))
        t.daemon = True
        t.start() 
        #os._exit(0) # Uncomment to exit without SIGCHLD
    join(tl) 

def handleExit():
    print("PID:", os.getpid(), "EXITING!")

def handleChildExit(arg1, arg2):
    print("PID:", os.getpid(), "CHILD EXITING!")

def main():
    signal.signal(signal.SIGCHLD, handleChildExit)
    atexit.register(handleExit)
    if True: # Change to False to run from main thread and get parent signaled when child is done.
        t = threading.Thread(target=runFork)
        t.daemon = False
        t.start()
        t.join() 
    else:
        runFork()

if __name__ == "__main__":
    main()