How can I "watch" a file for modification / change? [duplicate]

Question

I would like to invoke my chrome or firefox browser when a file that I specify is modified. How could I "watch" that file to do something when it gets modified?

Programmatically it seems the steps are.. basically set a never ending interval every second or so and cache the initial modification date, then compare the date every second, when it changes invoke X.

Answer 1

As noted, you can use pyinotify:

E.g.:

import webbrowser
import pyinotify

class ModHandler(pyinotify.ProcessEvent):
    # evt has useful properties, including pathname
    def process_IN_CLOSE_WRITE(self, evt):
            webbrowser.open(URL)

handler = ModHandler()
wm = pyinotify.WatchManager()
notifier = pyinotify.Notifier(wm, handler)
wdd = wm.add_watch(FILE, pyinotify.IN_CLOSE_WRITE)
notifier.loop()

This is more efficient than polling. The kernel tells you when it does the operation, without you having to constantly ask.

Answer 2

The Linux Kernel has a file monitoring API called inotify. A python binding is pyinotify.

With it, you can build what you want.