gistfile1.php

<?php

// LOGOUT LINK IN MENU

function diww_menu_logout_link( $nav, $args ) {
	$logoutlink = '<li><a href="'.wp_logout_url().'">Logout</a></li>';
	if( $args->theme_location == 'primary' ) {
		return $nav.$logoutlink ;
	} else {
	return $nav;
	}
}

add_filter('wp_nav_menu_items','diww_menu_logout_link', 10, 2);