Magento - How to check admin user logged in magento

- To get Admin users collection or all the the admin users details,

Mage::getModel('admin/user')->getCollection();

- To get admin role,

$getUser = Mage::getSingleton('admin/session')->getUser();

$getUser->getRole()->getData('role_id');

- To check admin user logged in or not using,

Mage::getSingleton('core/session', array('name'=>'adminhtml'));
if(  Mage::getSingleton('admin/session')->isLoggedIn() )
{
    $getUser = Mage::getSingleton('admin/session')->getUser();
    echo $getUser->getData('username');
}