Checking the type of file uploaded

Hello All,

I’m tring to develop my first plugin, but I need a little help. My plugin is dependent on a file being uploaded when the user is writing the post. Is there a way to check for the type of file(txt, mp3, jpg) that was added to the media library? In my example, I need to check and verify if an xml file was uploaded.

Or if possible, if I link to a file, how can I check if it is an XML file that is being linked to? I’m guessin that would be my action/filter. if a link to an xml file is present, do this…

Any help would be appreciated. Thanks in advance.