check user login or not in magento

Not: unauthorized user Redirect to login page with "$beforAutoUrl " URL and after login redirect to "$beforAutoUrl" url
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if( !Mage::getSingleton( 'customer/session' )->isLoggedIn() ){
$session = Mage::getSingleton('customer/session');
$beforAutoUrl = Mage::getBaseUrl('web').str_replace('/clients/omegabanners/','',$_SERVER['REQUEST_URI']);
$beforAutoUrl="";
$session->setBeforeAuthUrl($beforAutoUrl);

Mage::app()->getResponse()->setRedirect(Mage::getUrl("customer/account/login"));
}else{

echo "User Loged In"
}