Using the Incron file watching daemon

Check out the man page for incron and also this write-up by Nixcraft.

basic usage:

incrontab -e

In your editor of choice, follow this syntax:

<path-to-watch> <event mask> command

Links

http://linux.die.net/man/5/incrontab

http://www.cyberciti.biz/faq/linux-inotify-examples-to-replicate-directories/