That seems to be a rather interesting gksu bug or misbehaviour: "gksu whoami" does cache the password through sudo, but "gksu whoami > /tmp/o" doesn't. So the output redirection breaks this somehow.
That seems to be a rather interesting gksu bug or misbehaviour: "gksu whoami" does cache the password through sudo, but "gksu whoami > /tmp/o" doesn't. So the output redirection breaks this somehow.