how to use rwho?

I tried to see how to rwho works.

I have a /usr/spool/rwho directory with the following files in it:

whod.Serveur_qnx
whod.estape_qrtp_2
whod.val_22076
whod.val_22089

with, of course, some guys logged on these machines.

when I execute rwho, nothing is displayed.

any idea?

Alain.