I've got 'iwatch' looking at a directory, and when a particular file is created I want to run an rsync.

The catch is,.. if 10 files are created simultaneously, I dont want 10 scripts running rsync jobs.

Im thinking the only way to do this is to have a queue process which notes the file that was made in a text file serially, and a sync process which reads that file one line at a time and syncs them.

What say you?

Don't know anything about iwatch, but can you time it to only check once a minute, hour, or day or something? Can you write the script to check first and see if there are other instances running already and then exit and let the first instance finish? Not sure if that second option has other complications; like it doesn't fully sync because the directory state was not yet resolved. But that would be the job of the next iteration anyways. The whole problem is if checking is being performed at the same time alteration is occuring; then the follow on action may not be timed properly or fully effective because the directory was in transition.

Check this out:
http://vicerveza.homeunix.net/~viric/soft/ts/