Find Duplicates Automatically from Facebook Friends

I'm asking here, as I think it can be done with a simple command or two, though I'm unfamiliar with such commands. Yes I know about the commands in general, like sed and grep and everything. But I don't really know the complete list or how to use them. So since I'm pretty sure it's a simple command or two, I'm asking here. I don't think I need to write my own program for it.

I need to know, if I have a list of facebook friends, I manually created, and I get rid of the niceties in the file, and just have a list where each item begins with a star (*), then a space, and then the name of a facebook friend, and you can assume I typed it right for this simple task. Each line, of course ends with a newline, now how do I take that list and filter out the duplicates? This is the first task of this kind I've needed to do (lucky me). I don't know where else besides the linux mint forums to ask for how to do it, and I don't yet know how to search for it, but I'd love to learn. I just don't know what words to give the search engine. Maybe I think of them later? Anyway, I'm sure others know how to do this on Linux Mint command line, simply in a few seconds. I don't yet.