how to get attached file url for current post?

try get_pages with

'child_of' => get_the_ID(),
'parent' => get_the_ID(),

If you need i can post full code

EDIT :

if ( is_singular('post') ) {
    $args = array( 
        'post_type' => 'attachment',
        'posts_per_page' => -1, 
        'post_status' => null, 
        'parent' => $post->ID ,
        'child_of' => $post->ID,
        'sort_order' => 'desc'
    );
    $attachments = get_pages( $args );
    if ( $attachments ) {
        foreach ( $attachments as $attachment ) {
            echo wp_get_attachment_url( $attachment->ID ); 
        }
    }else {
    }
}

I hope this code help you