LoginLink

function loginlink(){
if (is_user_logged_in()) { ?>
    <a href="<?php echo wp_logout_url(get_permalink()); ?>">Log Out</a>
<?php }

else {?>

    <a href="<?php echo wp_login_url(get_permalink()); ?>">Log In</a>
<?php }
}

add_shortcode('login_link', 'loginlink');