Cleaning 2" copper pipe

[tacomaguy20]

Hi guys, I got a good deal on some copper pipe but its old and not exactly the best looking pipe you've ever seen. I was wondering how to clean it up. I went to lowes and found some stuff (forget what its called) for cleaning the outside of the pipe but what do you use to clean the inside? I have about 4 feet to clean. I don't imagine its dirty like the outside but still needs a little cleaning. Appreciate the help.