Remove Controller and it's method form codeigniter

How to remove Controller in  codeigniter and it's method just show it's parameter in url for ex:


http://localhost:90/CodeIgniter_2.1.4_new/category/show/this-is-the-test.html
as
http://localhost:90/CodeIgniter_2.1.4_new/this-is-the-test.html

Goto routes.php under config directory:
write this listed below line
$route['(:any)'] = "category/show/$1";
==============================

====================================================
create a new file "category.php"
<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');
class Category extends CI_Controller {
    public function index() {
        $this->load->view('welcome_message');
    }
    public function show($text) {
            echo "aaaaa".$text;  
    }
}