+If I<oping> is installed with the SetUID-bit, it will set the effective UID to
+the real UID before opening the file. In the special (but common) case that
+I<oping> is owned by the super-user (UIDE<nbsp>0), this means that privileges
+are temporarily dropped before opening the file, in order to prevent users from
+reading arbitrary files on the system.
+
+If your system doesn't provide I<saved set-user IDs> (this was an optional
+feature before POSIXE<nbsp>2001), the behavior is different because it is not
+possible to I<temporarily> drop privileges. The alternative behavior is: If the
+real user ID (as returned by L<getuid(2)>) and the effective user ID (as