http://example.com/subdir/?lold=13666 => http://www.example.com/subdir/?lold=13666

RewriteEngine On
RewriteCond %{HTTP_HOST} !^www\. [NC]
RewriteRule ^(.*)$ http://www.%{HTTP_HOST}%{REQUEST_URI} [R=301,L]

RewriteCond %{HTTP_HOST} ^!example.com$ [NC]
RewriteRule ^(.*)$ http://www.example.com/$1 [R=301,L]

This starts with the HTTP_HOST variable, which contains just the domain name portion of the incoming URL (example.com). Assuming the domain name does not contain a www. and matches your domain name exactly, then the RewriteRule comes into play. The pattern ^(.*)$ will match everything in the REQUEST_URI, which is the resource requested in the HTTP request (foo/blah/index.html). It stores this in a back reference, which is then used to rewrite the URL with the new domain name (one that starts with www).

[NC]表示不区分大小写的模式匹配，[R=301]表示使用代码301进行外部重定向(资源永久移动)，[L]停止所有进一步重写，并立即重定向。

试试这个:

RewriteEngine on
RewriteCond %{HTTP_HOST} ^example.com$ [NC]
RewriteRule ^(.*) http://www.example.com$1 [R=301]

RewriteEngine上 @ HTTP_HOST} ^yourdomain.com [NC] RewriteRule ^(.*)$ http://www.yourdomain.com/$1 [L,R=301]

检查这个完美的工作

    <VirtualHost *:80>
       DocumentRoot "what/ever/root/to/source"
       ServerName www.example.com

       <Directory "what/ever/root/to/source">
         Options FollowSymLinks MultiViews Includes ExecCGI
         AllowOverride All
         Order allow,deny
         allow from all
         <What Ever Rules You Need.>
      </Directory>

    </VirtualHost>

    <VirtualHost *:80>
      ServerName example.com
      ServerAlias *.example.com
      Redirect permanent / http://www.example.com/
    </VirtualHost>

这就是上面代码所发生的情况。第一个虚拟主机块检查请求是否为www.example.com，并在该目录下运行您的网站。

如果做不到这一点，就进入第二个虚拟主机部分。在这里，除www.example.com之外的任何内容都被重定向到www.example.com。

这里的顺序很重要。如果你先添加第二个virtualhost指令，它将导致一个重定向循环。

此解决方案将重定向到您的域www.yourdomain.com的任何请求。

干杯!

我使用的代码是:

RewriteEngine On
RewriteBase /
RewriteCond %{HTTP_HOST} ^www\.(.*)$ [NC]
RewriteRule ^(.*)$ http://%1/$1 [R=301,L]