creates a [restrict_pcs] that you can use to restrict some contents of your posts or pages

oaf-restrict-partial-content-shortcode.php

<?php
/*
Plugin Name: OAF Restrict Partial Content Shortcode
Plugin URI: https://www.oscarabadfolgueira.com
Description: This plugin creates a [restrict_pcs] that you can use to restrict some contents of your posts or pages.
Version: 1.0
Author: Oscar Abad Folgueira
Author URI: https://www.oscarabadfolgueira.com
License: GPLv2 only
License URI: http://www.gnu.org/licenses/gpl-2.0.html
*/

function oaf_restrict_partial_content_shortcode( $atts, $content = null ) {
	if ( is_user_logged_in() && !is_null( $content ) && !is_feed() ) {
		return $content;
	} else {
		return __( 'Upps! Este contenido sólo está disponible para usuarios registrados.', 'oaf_rpcs' );
	}
}

add_shortcode ('restrict_pcs', 'oaf_restrict_partial_content_shortcode' );