<?php if (S2MEMBER_CURRENT_USER_IS_LOGGED_IN){ ?>
  <a href="<?php echo S2MEMBER_LOGIN_WELCOME_PAGE_URL; ?>">My Account</a>
  | <a href="<?php echo S2MEMBER_LOGOUT_PAGE_URL; ?>">Logout</a>
<?php } ?>

---- s2member Shortcode Equivalent ----

[s2Get constant="S2MEMBER_LOGIN_WELCOME_PAGE_URL" /]