how to add/remove www. from domain name in .htaccess

to add/remove www. with mod writing :cd public_htmlvim .htaccess# vanish wwwRewriteEngine OnRewriteCond %{HTTP_HOST} ^www\.(.*)$ [NC]RewriteRule ^(.*)$ http://%1/$1 [R=301,L]# append wwwRewriteEngine OnRewriteCond %{HTTP_HOST} !^www\.(.*)$ [NC]RewriteRule ^(.*)$ http://www.%{HTTP_HOST}/$1 [R=301,L]