How to use a WordPress’ existing admin icon?

I use the add_menu_page function to add an new admin menu:

add_menu_page(
    'Custom_menu',
    'Custom_menu',
    'edit_posts',
    'custom_slug',
    '',
    'wordpress_existing_icon',
    5
);

How to use one of WordPress’ existing icons?

For instance, if I would like to use the “Posts” WordPress icon, by what must I replace 'wordpress_existing_icon' in the code above ?

I tried 'edit' and 'edit-posts' but it doesn’t work.

add_menu_page(); as far as I can tell does not work with screen_icon or the default CSS parameters. The $icon paramater only takes 2 options, an url or div (well 3 if you leave it empty), so that leaves you with these options:

1. Hard-code the link to the icons which are located in wp-includes/images/wpicons.png. This is an image slice of all the icons.

2. Just cut out the icon you want in a photo editor and include it as a stand-alone image in your plugin folder like the codex example.

3. Use the div parameter and define it via CSS. For example;

–

 add_menu_page(
               'custom menu title', 
               'custom menu', 
               'add_users', 
               'myplugin/myplugin-index.php', 
               '', 
               'div', //this part
               6);

To elaborate on the previous answer when using screen_icon('edit'); here is the list:

• edit
• upload
• link-manager
• edit-pages
• edit-comments
• themes
• plugins
• users
• tools
• options-general

You can also contain them in a div like :

<div id="icon-edit" class="icon32"></div>

Style reference: http://codex.wordpress.org/User:Wycks/Styling_Option_Pages: