How to overwrite magento controller in local pool

For Example you have to overwrite Mage/Contacts/controller/IndexController.php

Step 1: First you have to make a xml in app/etc/modules/
with name CompanyName_NameSpace.xml

<?xml version="1.0"?>
<config>
  <modules>
    <CompanyName_NameSpace>
      <active>true</active>
      <codePool>local</codePool>
      <version>0.1.0</version>
    </CompanyName_NameSpace>
  </modules>
</config>



Step2: You have to create the folders if not exist in
local/CompanyName/NameSpace/etc/
local/CompanyName/NameSpace/controllers/

In etc folder you have to create a config.xml file
<?xml version="1.0" encoding="utf-8"?>
<config>
    <frontend>
        <routers><!--Depending on the controllers area "frontend" or "admin" -->
            <contacts><!-- base module to rewrite -->
                <args>
                    <modules>
                         <CompanyName_NameSpace before="Mage_Contacts">Shweta_Newscontacts</CompanyName_NameSpace>
                    </modules>
                </args>
            </contacts>
        </routers>
    </frontend>
</config>




In controllers folder copy the Mage/Contacts/controller/IndexController.php file and include the lines:

include_once('Mage/Contacts/controllers/IndexController.php');
and
change the class name as:
class CompanyName_NameSpace_IndexController extends Mage_Core_Controller_Front_Action


Now apply changes in the file you wanted.
Now also, Magento take local pool file instead of core pool.