UI is an admin utility that renames existing users and adds users to a group.
ui is a user information utility that can display user information, list users from a given UID (or UID 500 by default), add a user to a group, rename a user along with his home directory and update his home directory files to reflect that change, list expired or locked users, change the shell for a user, and list users in an existing group.
Command line options:
-G group Adds user to a group.
-g group Shows users in the specified group.
-h This help.
-i Shows user information. This is the default option.
-l [UID] Lists users beginning with UID and upward. Defaults to 500.
-p Lists to default or specified printer.
-v Displayes version information.
-s Change user's shell type.
-x Lists expired or locked user accounts.
-m newname Move user. Changes users name and updates all records and config files.
Some options may be stacked such as -ip username or -lp username.