Automatically overwrite destination file with source file whenever the destination file gets overwritten by an external process.

stickfile.py

#!/usr/bin/env python
 
import os
from sys import argv, exit
from shutil import copyfile
from pyinotify import *
 
def add_watch():
    global watch_manager, watch_descriptor, file_to_stick
    watches = watch_manager.add_watch(file_to_stick, IN_MODIFY | IN_DELETE_SELF)
    watch_descriptor = watches[file_to_stick]
 
def remove_watch():
    global watch_manager, watch_descriptor
    watch_manager.rm_watch(watch_descriptor)
 
class MyProcessEvent(ProcessEvent):
    def process_IN_DELETE(self, event):
        self.stick_file()
 
    def process_IN_MODIFY(self, event):
        self.stick_file()
 
    def stick_file(self):
        global file_to_stick, file_to_clone
        print 'Sticking %s as %s' % (file_to_clone, file_to_stick)
        remove_watch()
        copyfile(file_to_clone, file_to_stick)
        add_watch()
 
if __name__ == '__main__':
    if len(argv) != 1+2:
        program_name = argv[0]
        print 'Usage %s: FILE-TO-CLONE FILE-TO-STICK' % (program_name)
        exit(1)
 
file_to_clone = argv[1]
file_to_stick = argv[2]
 
watch_manager = WatchManager()
notifier = Notifier(watch_manager, MyProcessEvent())
add_watch()
 
while True:
    try:
        notifier.process_events()
        if notifier.check_events():
            notifier.read_events()
    except KeyboardInterrupt:
        notifier.stop()
        break