.htaccess rewrite to subfolders for subdomains and the main domain

There's tons of resources online about using .htaccess to rewrite your subdomains and if need be, also rewrite your main domain to a subfolder. I have found plenty answers and most of them are exactly the same. I have been tediously testing these methods and I have the same problem in all cases.

Consider the wanted result:

maindomain.com : rewrite to /public_html/mainsite/

sub.maindomain.com : rewrite to /public_html/sub/

The fastest/cleanest way i have considered is the following:

RewriteEngine On

# Rewrite the main domain
RewriteCond %{HTTP_HOST} !sub.maindomain.com
RewriteCond %{REQUEST_URI} !^/mainsite
RewriteRule ^(.*)$ /mainsite/$1 [L]

# Rewrite the sub domain
RewriteCond %{HTTP_HOST} sub.maindomain.com
RewriteCond %{REQUEST_URI} !^/sub
RewriteRule ^(.*)$ /sub/$1 [L]

This works well except for 1 annoying issue; The line

RewriteCond %{REQUEST_URI} !^/mainsite

Basically prevents a rewrite loop, but if you browse to maindomain.com/mainsite/ it rewrites to /public_html/mainsite/ instead of /public_html/mainsite/mainsite/ hoping to raise a 404 not found. If i remove that line, i get a 500 server error as it goes into a loop :S

The issue is, that any one o开发者_如何学编程f these domains needs freedom of creating folders etc. and would like to ensure that there is absolute freedom in the sub-sub folders people create :S

Please could someone help here?

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RewriteEngine On

# Rewrite the main domain
RewriteCond %{HTTP_HOST} !sub.maindomain.com
RewriteCond %{REQUEST_URI} !^/mainsite/.*
RewriteRule ^(.*)$ /mainsite/$1 [L]

# Rewrite the sub domain
RewriteCond %{HTTP_HOST} sub.maindomain.com
RewriteCond %{REQUEST_URI} !^/sub/.*
RewriteRule ^(.*)$ /sub/$1 [L]

You need to make it so that it does not match any file within the /mainsite directory not just the root (/mainsite). I would think you would need to do the same to the sub domain also.

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actually try this if you are still looking for an answer

RewriteEngine On 
# Rewrite the main domain 
RewriteCond %{HTTP_HOST} !sub.maindomain.com 
RewriteCond %{REQUEST_URI} !^/mainsite/.* 
RewriteRule ^/mainsite/(.*)$ /mainsite/$1 [L] 

# Rewrite the sub domain 
RewriteCond %{HTTP_HOST} sub.maindomain.com 
RewriteCond %{REQUEST_URI} !^/sub/.* 
RewriteRule ^/sub/(.*)$ /sub/$1 [L]`