xxx.example.com から www.example.comへのリダイレクト方法の例
RewriteCond %{HTTP_HOST} !^www\.example\.com [NC]
RewriteCond %{HTTP_HOST} !^$
RewriteRule ^/(.*) http://www.example.com/$1 [L,R=301]xxx.example.com から example.comへのリダイレクト方法の例
RewriteCond %{HTTP_HOST} !^example\.com [NC]
RewriteCond %{HTTP_HOST} !^$
RewriteRule ^/(.*) http://example.com/$1 [L,R=301]Reference
Apache module mod_rewritehttp://httpd.apache.org/docs/1.3/mod/mod_rewrite.html
Apache URL Rewriting Guide
http://httpd.apache.org/docs/1.3/misc/rewriteguide.html
Apache URL Rewriting Guide (和訳)
http://japache.infoscience.co.jp/rewriteguide/