Questions[inotify](server)

I want to monitor special path to any event of create or modified files recursively in it via inotifywait but I don't know what's my problem is.

I have some folders that I want to exclude.

watchpath
    ->  folder1
        -> file1
        -> ingnorefile1 [IGNORE]
    ->  ignorefolder1 [IGNORE]

How do I correctly exclude them using a regular expression?

inotifywait -mr --exclude '(ignorefolder1|folder1\/ingnorefile1)' -e modify -e create -e delete . | while read date time dir file; do

What is correct regular expression to use to accomplish my goal?

I have an app farm which generates thumbnails and makes them available to a web server farm using nfs. However the performance is so poor so I am going to make a local copy of the files on each web node.

I looked at unison and lsync, but there doesn't seem to be a rpm available from the centOS5.5 repo for either.

which one should I use, or some other strategy. I critically need the sync to be immediate as the user needs to display the thumbnail straight away on a web page, so inotify based tools are good!

Edit: when I say immediate, I mean pushed out rather than pulled on some schedule.

In the end, lsync have released some more versions so I used that, and lsync works well once it is running (ie syncs in a few seconds) however it needs to enumerate each directory beforehand and for a very large file-system takes many hours..

Each time I make some changes to a file and save, I'd like a command to run. I can set up a Ruby script that could monitor the file and run the command as I'd like, but it occurs to me that there should be some simple Unix way to do this. Is there? I'm on Ubuntu 8.10, to be slightly less vague.

Edit:

incron was suggested, and looks good. But I'm having trouble getting it to work (edit: the command doesn't seem to run when I save a file in the specified directory, or my command is faulty). I installed incron and set up my user's incron table using incrontab, and added the user to the allowed list. My specific situation is editing a TeX file. I want the command to render it as a PDF to run every time I edit and save the TeX file. So this is the incron table entry I came up with:

/home/ehsanul/Documents/latex IN_CLOSE_WRITE echo $@/$# | grep \\.tex$ | xargs xelatex

What am I doing wrong?

I want to automatically run a script whenever new files are copied into a particular directory. In other words, is there a way in Linux to "watch" a directory for changes and then run something in response to the change?

It takes forever to back up. Before we can trust btrfs or ZFS to backup incremental snapshots, wouldn't it be nice if there was a daemon that used inotify to keep track of which files had actually changed so backups would run more quickly? Where is this program?

How do I backup my Linux box without having to crawl the whole filesystem every time? I would like a program that would detect the new or changed photos, source code, etc. and queue them to be copied over to my NAS.