WordPress at a glance
filter is not described

wp_get_attachment_url filter-hook . WP 2.1.0

Filters the attachment URL.

Usage

add_filter( 'wp_get_attachment_url', 'filter_function_name_5666', 10, 2 );
function filter_function_name_5666( $url, $attachment_id ){
	// filter...

	return $url;
}
$url(string)
URL for the given attachment.
$attachment_id(int)
Attachment post ID.

Where the hook is called

wp_get_attachment_url()
wp_get_attachment_url
wp-includes/post.php 5365
$url = apply_filters( 'wp_get_attachment_url', $url, $post->ID );

Where the hook is used (in WP core)

Does not used.