How to mass-change custom field value of a custom field name in wordpress

Is there any way to assign a random value to a custom field for each post !

Wp plugin are available to change the mass value of custom field but in my case i would like to assign random value to the custom field name for each post!

i try the code below but for some reason i m not able to make it work !

Will be great if someone can figure this out !

add_action('publish_page', 'add_custom_field_automatically');
add_action('publish_post', 'add_custom_field_automatically');
function add_custom_field_automatically($post_ID) {
    global $wpdb;
       $rand_num = rand(144, 544);
    if(!wp_is_post_revision($post_ID)) {
        add_post_meta($post_ID, 'views', '$rand_num', true);
    }
}

PHP:

here views is the custom field name and $rand_num is the random nu generated between 144 and 544 !

But this is not working!

 

What is happening instead of the expected behaviour? What (if anything) have you already done to debug it?