I would like to make a game (program) under linux or unix. However, I don''t know how to play wav file under linux. Can anyone help me or give me some reference on it?

Not a direct answer, but you may find what you are looking for with PortAudio. PortAudio is a free, open source, multi-platform audio API which can be targetted for Windows, Mac, Linux, Unix, BeOS and a few other platforms too, all with a generic API which is ( in my opinion ) a heck of a lot nicer than most platform specific audio API''s. The source is really cleanly written too, so if you have issues with using other peoples code you should be able to develop your own Unix/Linux audio libs from these.

Oh, and cross-posting is generally regarded as a netiquette no-no.