It's pretty simple to list all the mysql users on your system. All of the users information are stored in the MySQL table named mysql. To have MySQL print a list of all users, log in to MySQL with sufficient privliges and execute the following MySQL statement:
use mysql;select user from user;
Well, it's actually two MySQL statements separated by the ';'. The first statement tells MySQL to use the database named mysql. The second statement selects the individual user names from the user table of the mysql database.
And that's all you have to do in order to list users of a mysql server.