User-agent: *

# CANONICAL ROBOTS.TXT
<IfModule mod_rewrite.c>
 RewriteBase /
 RewriteCond %{REQUEST_URI} !^/robots.txt$ [NC]
 RewriteCond %{REQUEST_URI} robots\.txt [NC]
 RewriteRule .* http://example.com/robots.txt [R=301,L]
</IfModule>