二级域名访问指定文件
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^.*$ - [NC,L]
RewriteCond %{HTTP_HOST} ^admin.
RewriteRule (.*) admin.php [NC,L]
RewriteRule (.*) index.php [NC,L]
</IfModule>当访问域名 http://admin.* 时将访问 admin.php