python script to use linux kernel's inotify to monitor a single file, notifying the user through gnome shell's notification using notify2 python module.

watch-file

#!/usr/bin/env python3
# coding: utf-8

import contextlib
import os
import sys

from inotify.adapters import Inotify
from inotify.constants import IN_DELETE, IN_MODIFY, IN_MOVED_TO
import notify2 as notify


MODIFIED = (IN_DELETE | IN_MODIFY | IN_MOVED_TO)


@contextlib.contextmanager
def watch_directory(dirpath, mask=MODIFIED):
    assert os.path.isdir(dirpath)
    dirpath = os.path.abspath(dirpath).encode('utf-8')
    i = Inotify(block_duration_s=24*60*60)
    try:
        i.add_watch(dirpath, mask)
        yield i
    finally:
        i.remove_watch(dirpath)


def watch_file(filepath):
    filepath = os.path.abspath(filepath)
    dirpath, filename = os.path.split(filepath)
    filename = filename.encode('utf-8')
    with watch_directory(dirpath) as watcher:
        for event in watcher.event_gen():
            if event is not None and event[3] == filename:
                yield event[1]


if __name__ == '__main__':
    f = sys.argv[1]

    notify.init(f)
    n = notify.Notification('File Modified', f, 'text-x-generic-symbolic')

    for event_types in watch_file(f):
        n.show()