Shortcode?

Did anything become of the ability to make a shortcode? I tried my had at it but this seems to only work on posts that have a permalink category selected, those that only have one category to begin with don’t work

//shortcode for primary category
function primary_cat_shortcode($atts) {
 global $post;
  $cat_id = get_post_meta( $post->ID , '_category_permalink', true );
     if ( $cat_id != null ) {
	$cat = get_category( $cat_id );
	$category_link = get_category_link( $cat_id );
	$category_name = $cat->name;
     } else {
	$cat = get_the_category();
	$category_link = get_category_link( $category->term_id );
	$category_name = $cat[0]->cat_name;
     }
     $primary_cat_link= '<a href="'.$category_link.'">'.$category_name.'</a>';
 return $primary_cat_link;
}
add_shortcode('primary_cat', 'primary_cat_shortcode');