atomic_rename.py

atomic_rename.py

#!/usr/bin/python3

from argparse import ArgumentParser
import os
from os.path import dirname, realpath
from tempfile import NamedTemporaryFile

def syncdir(d: str):
    fd = os.open(d, os.O_RDONLY|os.O_DIRECTORY)
    os.fsync(fd)
    os.close(fd)

def atomic_rename(f: str):
    d = dirname(realpath(f))
    with NamedTemporaryFile(dir=d, delete=False) as t:
        t.write(b'abc\n')
        t.flush()
        os.fsync(t.fileno())
    os.rename(t.name, f)
    print('rewrote', f)
    syncdir(d)

def main():
    p = ArgumentParser()
    p.add_argument('file', metavar='FILE')
    ns = p.parse_args()
    atomic_rename(ns.file)

if __name__ == '__main__':
      main()