Question about RewriteRule and HTTP_HOST server variable

In evaluating a rewrite rule that redirects to a specific URL and say the rewrite condition is met, would it be possible to use HTTP_HOST as part of the URL to be redirected to?

Example in question:

RewriteRule .*\.(jpg|jpe?g|gif|png|bmp)$ http://%{HTTP_HOST}/no-leech.jpg [R,NC]

The motive behind this question is a desire to create a single htaccess file that would match against an addon domain (on a shared hosting account) and an infinite amount of subdomains below it to prevent hotlinking of images.

From serverfault $pageUsers[$entry.posts[0].author].name

• You can use %1 (and %2, etc) to access matches in preceding RewriteCond statements:

  RewriteEngine On
  # don't redirect no-leech.jpg or we'll end up in a loop
  RewriteCond %{REQUEST_URI} !^/no-leech.jpg$
  # match Host header and store
  RewriteCond %{HTTP_HOST} (.*)
  RewriteRule \.(jpg|jpe?g|gif|png|bmp)$ http://%1/no-leech.jpg [R,NC,L]
  

  Test:

  # GET -Sd http://localhost/foo.jpg
  GET http://localhost/foo.jpg --> 302 Found
  GET http://localhost/no-leech.jpg --> 200 OK
  

  And with a different Host header:

  # GET -SedH 'Host: foo.bar.com' http://localhost/foo.jpg
  GET http://localhost/foo.jpg --> 302 Found
  GET http://foo.bar.com/no-leech.jpg --> 200 OK
  

  From markdrayton