The problem is, for rar files, I haven't found anything outside of RarLabs' CLI unrar util.
sharp256, the main command you need is [code:1:5df5639b55]cd location_of_rar_file
unrar e name_of_rar_file[/code:1:5df5639b55]
Edit: Even still, be sure to check out the command usage, as linux_0 said.