Execute a shell script when a file changes in Linux

We are using Red Hat Linux OS. We need to execute a shell script whenever a particular file changes or a new file is created in a particular directory. We do not want to run a "cron" job to check this file or directory on a regular basis. We need a "push" or you can call "event" based solution so that the shell script executes real-time whenever this file changes or a new file is created in a particular directory. You can write it as a 'c' program so that we can run it as a daemon. If you have a better suggestion, let me know too. ## Deliverables 1) Complete and fully-functional working program(s) in executable form as well as complete source code of all work done. 2) Deliverables must be in ready-to-run condition, as follows (depending on the nature of the deliverables): a) For web sites or other server-side deliverables intended to only ever exist in one place in the Buyer's environment--Deliverables must be installed by the Seller in ready-to-run condition in the Buyer's environment. b) For all others including desktop software or software the buyer intends to distribute: A software installation package that will install the software in ready-to-run condition on the platform(s) specified in this bid request. 3) All deliverables will be considered "work made for hire" under U.S. Copyright law. Buyer will receive exclusive and complete copyrights to all work purchased. (No GPL, GNU, 3rd party components, etc. unless all copyright ramifications are explained AND AGREED TO by the buyer on the site per the coder's Seller Legal Agreement). ## Platform Red Hat Linux