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WhatsOpen is a MacOSX utility designed to aid you in determining what is holding your files open. You can generate a list of all open files, filter the files, kill the applications holding files open, lookup information on process etc...
Works as advertised
If you have files that are preventing the Trash from emptying or volumes that won't eject, this easy to use utility does the job.
I bought this app thinking for an alternative to the option to "force quit" an application, but this app (whatsopen) is very messy in what is shows that is open in the system. Would be nice if the app categorized with icons istead of text. I prefer to "force quite" an app instead of use this app.