How to show user_name?

I use

<?php wp_register(); ?>
<?php wp_loginout(); ?>

add a login panel on the top of my page.
but when I login in, it just show * Site Admin * Log out
I have tied some diffrent users, they all show * Site Admin
I noticed the login information in wp-includes/general-template.php line 254-296, how to modify the code that can show welcome username, * Site Admin * Log out thanks.

Iā€™m first to admit that my PHP foo is not strong, and this is untested, but should work:

if ( is_user_logged_in() ) {
    global $display_name;
    echo "Welcome ".$display_name.",  ";
} else {


Thanks seriocomic,
I got the anwser from forum help.
This can show the username, But If I add a li tag like this , it can not show the li, do you have any idea? Thanks again.

if ( is_user_logged_in() ) {
	global $current_user;
echo 'welcome '.$current_user->user_login.'<br />';

echo '<li>';
echo '</li>';

right, echo ā€˜<li>ā€™ is a correct way.
Thanks php_daemon.