rename a file in package explorer (eclipse)

it's quite silly how difficult it is to find certain menu items it eclipse.  i wanted to rename a file for which i forgot the ".c" extension, but couldn't find out how to do it!  normally i'd try to convince eclipse to open the project folder using whatever interface (e.g. gnome), but i forget if that's possible and i can't even try because i now i'm getting a "Problem Occurred" / "PermGen space" error which pops up again immediately after i hit ok.  so to save you the lifetime's worth of trouble you may face if you try to rename a file in eclipse using your intuition, i've found a trick for you.

> select the file, hit f2.