"""Offline advisory-lock example, using only disposable local files."""
import fcntl,json,os,platform,tempfile
from pathlib import Path

def try_lock(file):
 try:
  fcntl.flock(file.fileno(),fcntl.LOCK_EX|fcntl.LOCK_NB)
  return True
 except BlockingIOError:return False

def run():
 with tempfile.TemporaryDirectory(prefix='reader-flock-lab-') as directory:
  path=Path(directory)/'job.lock'
  with path.open('w+') as first:
   assert try_lock(first)
   with path.open('r+') as same:
    before=try_lock(same)
    assert before is False
   original_inode=os.fstat(first.fileno()).st_ino
   path.unlink()
   with path.open('w+') as replacement:
    replacement_inode=os.fstat(replacement.fileno()).st_ino
    after=try_lock(replacement)
    assert original_inode!=replacement_inode and after is True
    result={'kind':'disposable_local_flock_example','performed_date_kst':'2026-10-24','environment':{'python':platform.python_version(),'system':platform.system()},'original_descriptor_still_open':not first.closed,'same_existing_path_second_lock_acquired':before,'recreated_path_points_to_different_inode':original_inode!=replacement_inode,'recreated_path_second_lock_acquired':after,'interpretation':'Locks target open file descriptions, not a permanent pathname identity. Deleting a lock path can produce a different target while an old descriptor remains open.','limits':'Same-process independently opened descriptions, local temporary filesystem; no cron, systemd, distributed or production jobs were exercised.'}
    fcntl.flock(replacement.fileno(),fcntl.LOCK_UN)
   fcntl.flock(first.fileno(),fcntl.LOCK_UN)
 return result
if __name__=='__main__':print(json.dumps(run(),ensure_ascii=False,indent=2))