Get author full name

Try the following:

<?php

$fname = get_the_author_meta('first_name');
$lname = get_the_author_meta('last_name');
$full_name="";

if( empty($fname)){
    $full_name = $lname;
} elseif( empty( $lname )){
    $full_name = $fname;
} else {
    //both first name and last name are present
    $full_name = "{$fname} {$lname}";
}

echo $full_name;
?>