#!/usr/bin/env python

from __future__ import print_function

import os
import sys
import time
from barman.lockfile import LockFile, LockFileBusy

if __name__ == '__main__':

    if len(sys.argv) != 2:
        print('Usage: %s file_to_lock' % sys.argv[0], file=sys.stderr)
        sys.exit(2)

    try:
        lock = LockFile(sys.argv[1])
        lock.acquire(raise_if_fail=True, wait=False)
        pid = os.fork()
        if pid == 0:
            # Child process: loop endlessly
            # detach from parent session
            os.setsid()
            # close every descriptor different from the locked file
            for fd in range(0, 1024):
                try:
                    if fd != lock.fd:
                        os.close(fd)
                except OSError:  # ERROR, fd wasn't open to begin with (ignored)
                    pass
            # loop forever
            while True:
                time.sleep(1)

        # Parent process: print the pid and exit
        print('%d' % pid)
        sys.stdout.flush()
        # To keep the acquired lock, we don't want any process cleanup
        # for the father process. Exit immediately.
        # noinspection PyProtectedMember
        os._exit(0)
    except LockFileBusy:
        print('Lock acquisition failed on file "%s"' % sys.argv[1])
        sys.stdout.flush()
        sys.exit(1)