. [ A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z ] . UNIX commands . access permissions . changing . default values for . displaying . restrictions on . understanding . addresses . for mail . mail, finding . alias . command name . using for mail address . archive (of files) . argument . quoting . passing to shell scripts . to command . arithmetic . done with expr command . ASCII . definition of . encode binary file as .