How to exclude certain sections of a site from Mod ReWrite Rules - mod-rewrite

Question

I am moving most pages from a site and I want to redirect all requests to a 404 error page except all/any pages in a certain cname on the site, all/any pages in a certain sub-directory on the site and a certain page in a certain directory on the site.
Here is what I have so far:
Options +FollowSymlinks
RewriteEngine On
RewriteCond %{HTTP_HOST} !^blogs.example.com [NC]
RewriteCond %{REQUEST_URI} !^/private [NC]
RewriteCond %{REQUEST_URI} !^/public/special-form.php [NC]
RewriteCond %{REQUEST_URI} !^/public/special-form_submitted.php [NC]
RewriteCond %{REQUEST_URI} !^/error404.php [NC]
RewriteRule ^(.*) http://example.com/error404.php [R=301,L]

Answer 1

Your issue is mainly the / at the start of your RewriteRule, why?
Because you're using it with an .htaccess so the RewriteRule path starts without the / at the begin.
If it was inside the VirtualHost then that would have worked just fine.
Basically this is what your rule is telling the server to do after our comments conversation and your update:
Options +FollowSymlinks
RewriteEngine On
# if domain is not blogs.example.com
RewriteCond %{HTTP_HOST} !^blogs.example.com [NC]
# and if address does not start with /private
RewriteCond %{REQUEST_URI} !^/private [NC]
# and if the file is not /public/special-form.php
RewriteCond %{REQUEST_URI} !^/public/special-form.php [NC]
# and if the file is not /public/special-form_submitted.php
RewriteCond %{REQUEST_URI} !^/public/special-form_submitted.php [NC]
# and if the file is not /error404.php
RewriteCond %{REQUEST_URI} !^/error404.php [NC]
# then redirect to http://example.com/error404.php
RewriteRule ^ http://example.com/error404.php [R=301,L]
So anything else including images or css or not listed on the conditions would be redirected, in order to avoid that you would have to verify all the needed files within those 2 php pages and white list it, for example with a condition like this:
RewriteCond %{REQUEST_URI} !^/public/[^.]+\.(css|pdf|jpg|doc)$ [NC]
Basically the above means anything within the public folder that ends with .css or .pdf or .doc or .jpg should be displayed.
NOTE: Keep in mind that if your images and documents and whatever else you need to show to your users from those 2 PHP pages are not within the public folder the above will not work, that was merely an example to illustrate an easy way to couple multiple types of files into it.
You could also resume this 2 conditions:
RewriteCond %{REQUEST_URI} !^/public/special-form.php [NC]
RewriteCond %{REQUEST_URI} !^/public/special-form_submitted.php [NC]
as follow:
RewriteCond %{REQUEST_URI} !^/public/(special-form_submitted|special-form)\.php [NC]
You would end with:
Options +FollowSymlinks
RewriteEngine On
RewriteCond %{HTTP_HOST} !^blogs.example.com [NC]
RewriteCond %{REQUEST_URI} !^/private [NC]
RewriteCond %{REQUEST_URI} !^/public/(special-form_submitted|special-form)\.php [NC]
RewriteCond %{REQUEST_URI} !^/public/[^.]+\.(css|pdf|jpg|doc)$ [NC]
RewriteCond %{REQUEST_URI} !^/error404.php [NC]
RewriteRule ^ http://example.com/error404.php [R=301,L]
Just a side information, since you're redirecting anything that does not match the conditions and you're not passing along anything to the redirect, you don't need the (.*), merely using ^ alone will do the job.