how to automatically add www prefix?

how to redirect all mydomain.com to www.mydomain.com

i have try

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

Code (markup):

it's only work for domain.com/something , not work for domain.com/forum/something

TIA

 

Try this:

Options +FollowSymLinks
RewriteEngine on
RewriteCond %{HTTP_HOST} ^domain\.com
RewriteRule ^(.*)$ http://www.domain.com/$1 [R=permanent,L]

 

This is what I use:

# Redirect to WWW

rewriteCond %{HTTP_HOST} !^www\.mysite\.com
rewriteRule ^(.*)$ http://www.mysite.com/$1 [L,R=301]

Code (markup):

 

thanks to all replies. i have tried your suggestion but still no luck

it works for example.com/forum ( no trailing slash )
but that doesn't work too for
example.com/forum/showthread.php
example.com/forum/

maybe need something more on rewriteRule condition?

Regards

 

Give this a try:

RewriteEngine On
RewriteCond %(HTTP_HOST) !^www.mydomain.com$ [NC]
RewriteRule ^(.*)$ http://www.mydomain.com/$1 [R,L]

 

@Cpucandy : thanks but still not working for mydomain.com/forum/