Check in the Loop if a post is password protected

Got this from https://comox.textdrive.com/pipermail/wp-testers/2008-November/010138.html

<?php
if (!empty($post->post_password)) { // if there's a password
if ($_COOKIE['wp-postpass_' . COOKIEHASH] != $post->post_password) {  // and it doesn't match the cookie
echo 'display of excerpt:' . $post->post_excerpt;
}
}
?>

The “if” block works, it understands if a post is password protected.

However $post->post_excerpt;
is empty.

Do someone knows why? Do I have to take some global variable before this code?

Could be you are talking about the ‘manufactured’ Excerpt so use template tag, the_excerpt() instead.