Link to subdomain index

Hello, I have 3 subdomains for each of my 3 main categories: movies.mydomain.com, books.mydomain.com and tvshows.mydomain.com. And of course the main index page: http://www.mydomain.com.

I want the equivalent of (get_bloginfo(“url”) to create links my subdomains. How can I do that? I tried to do something using <?php echo get_category_link($cat); ?> and <?php echo(get_bloginfo(“url”); ?> but I doesn’t work.

Any idea how to do that is welcome 🙂