How to watch directory for file modifications

Question

I'm on a mac. I've been using Launchd's WatchPaths directive to watch a directory for file changes. My script only triggers when a file is added or deleted from the watched directory.

However, the script does not trigger when a file is modified..

Essentially, I'm trying to create a DIY Dropbox for syncing my Sites folder.

Is there a way to do this via launchd, bash or python?

I think linux has something like inotify, but I am not aware of a solution for mac.

Answer 1

I tried my hand at the problem, using the MacFSEvents package (available on PyPI, too):

import os

from fsevents import Observer, Stream


def callback(file_event):
    print file_event.name # the path of the modified file


def main():
    observer = Observer()
    observe_path = os.getcwd() # just for this example
    stream = Stream(callback, observe_path, file_events=True)
    observer.start()
    observer.schedule(stream)


if __name__ == '__main__':
    main()

This will call callback any time a file is created, modified, or deleted (you can check which event occurred using the value of file_event.mask).

Note that you will probably want to observe on a thread outside of the main thread (the above program refuses to quit, even on KeyboardInterrupt). More information on the API can be found in the MacFSEvents README. Hope this helps!