I have a store created on X-Cart, and I want to add a functionality so the user's must login on a customer login before seeing any site contents/products. If user is not logged in she/he must be redirected to the login page.
In X-Cart 5 you can use "memberships" http://kb.x-cart.com/en/users/user_membership_levels.html to setup products as accessible by users with certain membership. So they will have to log in 1st to be able to see products configured to be accessible for certain membership customers.