Exit signal - work around the lack of UNIX signal in Windows

atexit.py

import atexit
import time
import logging
import signal
import os

def sighandler(sigcode, x):
    print("Signal Exit!!", flush=True)
    print([sigcode, x], flush=True)
    exitcall()
    os._exit(0)

def exitcall():
    print("Exit!!", flush=True)
    with open("a.txt", "w") as fp:
        fp.write("1")
    logging.warning("exit!")

def main():
    atexit.register(exitcall)
    termsigs = [getattr(signal, s) for s in dir(signal) if s in ["SIGABRT", "SIGINT", "SIGTERM", "SIGBREAK"]]
    print(dir(signal), flush=True)
    print(termsigs, flush=True)
    for sig in termsigs:
        signal.signal(sig, sighandler)
    while True:
        time.sleep(1)
    logging.warning("main end")

if __name__ == "__main__":
    try:
        main()
    finally:
        print("finally", flush=True)
        exitcall()

# The above is is test out the atexit mechanism as to write a daemon program
# See: https://github.com/msys2/msys2/wiki/Porting#signals-in-mintty
# Running Win CPython inside mintty interactively means the Ctrl-C signal
# is not sent to the program but intercepted by the terminal and ask the
# terminal to terminate the process abruptly. Cygwin CPython works as expected.
#
# Windows has SIGBREAK but Ctrl-C is SIGINT