How to determine if files are in use

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I recently inherited a Concrete5 website, but coming from a development background I'm picking it all up pretty quickly. If I can I'd like to go through the years of files this website has gone through and get rid of the ones that the website currently does not use. Is there a way, either through the File Manager, an add-on, or even some PHP magic, that I can tell if a particular file is being used on the site?