Singleton Process with PID Lock File #python

lockpidfile.py

import os
import fcntl
import contextlib
import time


@contextlib.contextmanager
def lockpidfile(filepath):
    with os.fdopen(
        os.open(filepath, os.O_RDWR | os.O_CREAT, mode=0o666),
        mode="r+",
        buffering=1,
        encoding="utf-8",
        newline="",
    ) as f:
        try:
            fcntl.lockf(f, fcntl.LOCK_EX | fcntl.LOCK_NB)
        except OSError:
            yield False
            return
        f.truncate()
        pid = os.getpid()
        f.write(f"{pid}\n")
        yield True
        fcntl.lockf(f, fcntl.LOCK_UN)
        try:
            os.unlink(filepath)
        except OSError:
            pass


def main():
    with lockpidfile("/tmp/lockpidfile.pid") as lockpidstatus:
        if not lockpidstatus:
            print("NOT GOOD - PROCESS ALREADY STARTED")
        else:
            print("OK!")
            time.sleep(15)


main()