I am developing a Wordpress theme but i can not obtain the current user title. I attempted get_currentuserinfo() however it appears doesn't work. Can there be any working function to obtain user title will be able to use within header.php template file?

Have you browse the documentation, this situation work nicely for me personally :

<?php 
  global $current_user;
  get_currentuserinfo();
  echo $current_user->user_login;
?>