php - Wordpress Featured Image URL -

i trying add featured image url featured image, open in lightbox when clicked.

my code is:

<?php if (have_posts()): while (have_posts()) : the_post(); ?>  <a href="#" target="_blank"><?php if ( has_post_thumbnail() ) { the_post_thumbnail();} ?></a>  <?php endwhile; ?>      <?php else: ?>          <article>              <h1><?php _e( 'sorry, nothing display.', 'html5blank' ); ?></h1>          </article><!--/ article -->  <?php endif; ?> 

i have tried quite few things cannot pull thumbnail url. have tried adding these link # is:

wp_get_attachment_thumb_url( get_post_thumbnail_id( $post->id ));          

...

$thumbnail_src = wp_get_attachment_image_src( get_post_thumbnail_id( $post->id ) ); 

...

<?php echo $thumbnailsrc ?> 

i sure there simple solution yet find. maybe able assist :-)

please try code adding in post loop. , confirm have set feature image post listings.

<?php $post_thumbnail_id = get_post_thumbnail_id( $post->id ); if(!empty($post_thumbnail_id)) { $img_ar =  wp_get_attachment_image_src( $post_thumbnail_id, 'full' ); ?>     <img src="<?php echo $img_ar[0];?>" /> <?php } ?>