Sloth

Sloth is a graphical frontend for the console tool lsof. If don't know what that is, it doesn't matter!

Sloth makes it easy to find out which applications are using which files.

Sloth displays a list of all open files and sockets in use by all the applications your user account is running on the system. This list is presented along with the names of applications using the file and their process IDs. Includes support for regex list filtering, process killing, sorting and more.