Wordpress user information show...

The call to get_currentuserinfo() places the current user's info into $current_user, where it can be retrieved using member variables.

<?php global $current_user;
    get_currentuserinfo();
 echo 'Username: ' . $current_user->user_login . "\n";
 echo 'User email: ' . $current_user->user_email . "\n";
 echo 'User first name: ' . $current_user->user_firstname . "\n";
 echo 'User last name: ' . $current_user->user_lastname . "\n";
 echo 'User display name: ' . $current_user->display_name . "\n";
 echo 'User ID: ' . $current_user->ID . "\n";
 ?> 

Output 
Username: Zedd

User email: my@email.com
User first name: John
User last name: Doe
User display name: John Doe

User ID: 1