Force template to show post author’s nickname

Hi there,

I’d like my template to always retrieve the authors nickname, and never their username, regardless of what is set in the users profile.

I did give the following a try, but I couldn’t make it work:

single.php
<?php
if(isset($_GET[‘author_name’])) :
$curauth = get_userdatabylogin($author_name);
else :
$curauth = get_userdata(intval($author));
endif;
?>

Post by: <?php echo $curauth->nickname;?>

Can anyone make a suggestion, or post some tips?
Thanks,
Chris