WordPress: Add a shortcode to use in the content that shows content to non-logged in users. If user is logged in then they will not see the content.

wp-shortcode-loggedin-loggedout.php

<?php

/**
 * Add A Shortcode allowing content for non-logged in users. 
 * Add to functions.php
 * This could used in a situation where you have gated content and the user needs to be logged in to view.
 * An example of usage is: [not_logged_in]You must be logged in to view this content[/not_logged_in]
 */
function check_user ($params, $content = null){
  //if the user is not logged in.  You can remove the ! if you want to change the statement to is logged in.
  if ( !is_user_logged_in() ){
    return $content;
  }
  else{
    return;
  }
}
add_shortcode('not_logged_in', 'check_user' );