codeigniter-rules

# CodeIgniter writing
RewriteCond $1 !^(index\.php|images|robots\.txt|css|user_files|subdomain1|subdomain2)
RewriteRule ^(.*)$ /index.php/$1 [L]

redirect-WITH-leading-www

# Redirect adding leading www to root domain if no subdomain is specified
RewriteCond %{HTTP_HOST} !^(subdomain1|subdomain2|www)\.example\.com$ [NC]
RewriteRule ^(.*)$ http://www.example.com/$1 [R=301,L]

redirect-without-leading-www

# Redirect deleting leading www to root domain if no specified subdomain is used
RewriteCond %{HTTP_HOST} !^(subdomain1|subdomain2)\.example\.com$ [NC]
RewriteCond %{HTTP_HOST} !^example\.com$ [NC]
RewriteRule ^(.*)$ http://example.com/$1 [R=301,L]