The best way to do this is make use of Middleware. Jeffrey Way made a great lesson about middleware in his Laravel 5 Fundamentals series here: https://laracasts.com/series/laravel-5-fundamentals/episodes/16

That way you don't have to copy & paste the same snippet of code for every controller method.

As above, but to get rid of the \ you just need to add a use at the top of the Controller:

use Auth;

You'll then be able to use Auth::check() in your code, without the \.

I didnt get anything back with Auth::check(), maybe it works, I dont know why, but this works.

if($user = Auth::user())
{
    // do what you need to do
}

IF you want to display something when not logged in, do this:

if(Auth::guest())
{
    // do what you need to do
}

works in 5.2.