Python Script monitor for file change

Question

I want to run a little python script on my Freenas inside a Jail.

The script should watch out for a file. If this file is changed. It should do something.

So my question is what is the mechanism which allows me to monitor a file and run a method when the file is changed (In detail the content of one specific file) or is there another method to just call a python script in such a case.

`pyinotify` or `inotify-tools` according to http://stackoverflow.com/a/12582773/320220 — beerbajay, Mar 03 '15 at 13:02
As far as I know there is no inotify for freebsd or is there? — TM90, Mar 03 '15 at 13:04
@PadraicCunningham I want to monitor one special file and do something when the file content is modified. — TM90, Mar 03 '15 at 13:05
Well, you could compare it's content to the previous version every few seconds... It seems pretty straightforward, so what's stopping you? Do you need this to be event based? Realtime? Without more information answering correctly can be tricky. — Reut Sharabani, Mar 03 '15 at 13:08
@TM90 Woops, quite right! I didn't notice it was non-linux, sorry! — beerbajay, Mar 03 '15 at 13:08
@ReutSharabani The most elegant solution would be an event based one. — TM90, Mar 03 '15 at 13:09
@TM90 I think that an update to the file is different than re-creation of the file, so that's information that needs to be included in the question. — Reut Sharabani, Mar 03 '15 at 13:10
You could try [watchdog](https://pypi.python.org/pypi/watchdog) which claims to support BSD. — mhawke, Mar 03 '15 at 13:13
I will take a look at watchdog and entr. Additionally I also found Kqueue — TM90, Mar 03 '15 at 13:15

score 2 · Accepted Answer · edited May 23 '17 at 11:56

That's job for kqueue. There are 2 possible bindigs for that... py-kqueue (all BSDs and OSX) and py-freebsd (just FreeBSD). Both in ports. Some hint how to use kqueue here: Check if file is modified deleted or extended using python select.kqueue()

Other example to understand kqueue in py-openbsd bindings docs: kqueue - openbsd. And then of course man kqueue.

Further option is to use Twisted async framework (which in background will use kqueue for reactor) and its FileMonitoringService. This is periodic checker, generic implementation - OS agnostic.

Python Script monitor for file change

1 Answers1