mod_rewrite in httpd/apache?

Question

I am a bit confused about the mod_rewrite documentation. It shows this rule to block hotlinking:

RewriteCond "%{HTTP_REFERER}" "!^$"
RewriteCond "%{HTTP_REFERER}" "!www.example.com" [NC]
RewriteRule ".(gif|jpg|png)$" "-" [F,NC]

however, I'd think a better rule would be:

RewriteCond "%{HTTP_REFERER}" "^$" [OR]
RewriteCond "%{HTTP_REFERER}" "!(www.)?example.com/.*$" [OR,NC]
RewriteRule ".(gif|jpg|png)$" "-" [F,NC]

if I want to block anyone manually typing in a link (no referer) + hotlinking (probably has a referer). Do i need the [OR] on the 1st
RewriteCond and not the 2nd one? It seems to work with OR on both conditions.

Answer 1

 RewriteCond "%{HTTP_REFERER}" "!^$"
 RewriteCond "%{HTTP_REFERER}" "!www.example.com" [NC]
 RewriteRule ".(gif|jpg|png)$"  "-" [F,NC]

Thats not what I see at http://httpd.apache.org/docs/current/mod/mod_rewrite.html but that doesnt really matter. I mention it only to point out that you really should be specific when stating what documentation you are reading. In this case a URL would have been a good idea.
however, Id think a better rule would be:

RewriteCond "%{HTTP_REFERER}" "^$" [OR]
RewriteCond "%{HTTP_REFERER}" "!(www.)?example.com/.*$" [OR,NC]
RewriteRule ".(gif|jpg|png)$" "-" [F,NC]

Also the [OR] on the second RewriteCond does nothing since it isnt followed by another RewriteCond. You also dont need the first RewriteCond since by definition an empty HTTP_REFERER wont match pattern.

Answer 2

If you want to forbid access to images when the referrer is empty, just remove the first RewriteCond (the case is caught by the second one already). The [OR] on the second one is ignored.