301 redirecting with a word match in URL

I am trying to redirect [via .htaccess] all the URLs in my forum which will contain this,

mode=linear

Example URL:

forums/showthread.php?mode=linear&tid=800&pid=1901

I want to redirect all URLs that will have "mode=linear" in it to a 404 not found page. The reason is that this mode thing create duplication problem.

Can someone help?

 

Does it have to be a 404, what about doing a 301 to the non-linear instead ?

Something like this for starters, I'm not sure what the potential querystrings will look like, but based on what you posted this would do the trick.

RewriteCond %{QUERY_STRING} ^mode=linear&tid=([0-9]+)&pid=([0-9]+)$
RewriteRule showthread\.php$ showthread.php?tid=%1&pid=%2 [R=301]

Code (markup):

 

thanks. You are right. I have done a redirect to the non linear URL instead of 404 page.