how an i echo just the id of an attachment?

$attachments =& get_children('post_type=attachment');
  foreach($attachments as $id=>$attachment){
    echo $id;
  }

Thanks!

But i dont think it works for me..

I list a lot of attachments from several post in my category.php.. every post got at least three attachments.. now when i put it in i just get the same attachment id on everything.

the reason why i need unique id’s is because i use quicksand to filter my attachments..

Take a look at this.
https://codex.www.ads-software.com/Template_Tags/get_posts#Show_all_attachments