How to print rewrite rules?

did you call global $wp_rewrite; ?

There are also plugins like the rewrite rules inspector. https://www.ads-software.com/plugins/rewrite-rules-inspector/

Also, the init hook would probably be best.

Yes, I called it. This is the code:

add_action('admin_menu', 'gp_call_add_rewrite_page');

function gp_call_add_rewrite_page() {
    add_menu_page('Rewrite Page', 'Rewrite Page', 'manage_options', __FILE__, 'gp_add_rewrite_page', 'dashicons-edit');
}

function gp_add_rewrite_page() {
    ?>
    <div class="wrap">
        <h2>Rewrite Page</h2>
        <?php
        global $wp_rewrite;
        var_dump($wp_rewrite);
        ?>
    </div>
    <?php
}

I set permalinks to /%postname%.html in Settings > Permalinks

I just tested, code works for me. Flush your rules perhaps.

I tried first time on 3.9-beta3 version so I tried also on 3.8.1 version but I can’t see any rules also flushing rules.

I found a solution, I don’t know if it is the best solution but it works.
I read directly from database using this line of code:

$rewrite_rules = get_option( 'rewrite_rules' );

and then I loop the array.