RewriteCond simply doesn't work, doesn't check properly if file exists

Question

Hey everybody.

I've been trying to solve this for hours now but came up with nothing.

Inside .htaccess, whenever somebody requests an image from a folder of my website, I'm trying to check if a file with the same name exists in another folder; if it does, return that file; if it doesn't, return the file originally requested.

It seems so easy but it simply doesn't work. The .htaccess code is as follows:

RewriteEngine On

RewriteCond /images/blog/watermark/$1 -f
RewriteRule ^(.*) /images/blog/watermark/$1

The "RewriteCond" always returns negative, so the image requested is always loaded as is. If I change it to, like,

RewriteCond %{REQUEST_FILENAME} -f

it always returns positive, so it gets the image from the folder I want - except when the image's not there, generating an error, which is exactly what I'm trying to prevent.

What am I doing wrong?

Thanks.

Answer 1

You have the wrong syntax for RewriteCond. You probably want to do something more like this:

RewriteCond ^/images/blog/watermark/(.*) -f

In this case $1 doesn't actually exist, because RewriteCond takes a regular expression, not a replacement string. So, Apache is looking for /images/blog/watermark/$1 instead of any file inside of /images/blog/watermark/.

For reference: http://httpd.apache.org/docs/1.3/mod/mod_rewrite.html#RewriteCond

Answer 2

I got it!

Apparently RewriteCond needs the whole directory structure to check file existence properly.

I added %{DOCUMENT_ROOT} before the path I previously had in my RewriteCond and it worked.

Also, after further reading the documentation, I noticed that the first group is $0 and not $1 when backreferencing from a RewriteRule.

So the final code is as follows:

RewriteEngine On 

RewriteCond %{DOCUMENT_ROOT}/images/blog/watermark/$0 -f 
RewriteRule ^(.*) /images/blog/watermark/$1