Automatically append login and logout links to a specific menu location.

nav-login-logout.php

<?php

add_filter( 
  'wp_nav_menu_items', 
  function( $items, $args ) {
	if ( 'primary_nav' === $args->theme_location ) {
		if ( is_user_logged_in() ) {
			$items .= '<li><a title="Log Out" href="' . esc_url( wp_logout_url() ) . '">' . __( 'Log Out', 'cobb-realtors' ) . '</a></li>';
		} else {
			$items .= '<li><a title="Login" href="' . esc_url( wp_login_url() ) . '">' . __( 'Login', 'cobb-realtors' ) . ' </a ></li >';
		}
	}

	return $items;
  }, 
  10, 
  2 
);