Vi ---> Saving and Quitting

     :w    write to disk
     ZZ    write to disk and exit
     :q!   exit without writing to disk

Actually, the command for quitting vi is :q. You can save and quit by typing :wq but ZZ does the same thing¹ and takes one less keystroke. If there are unsaved changes to the text and you try to quit using :q, vi will warn you that you have unsaved changes and will prevent you from quitting. In order to quit without saving the changes you must use the override switch, !.