UNIX systems record information about current and past log-ins in a user
accounting database. This database is realized by two files: File utmpx
contains a record of all users currently logged onto the system, while file
wtmpx contains a record of all log-ins and log-outs. Some systems (such as
HP-UX and AIX) also maintain a third file containing failed log-in attempts.
The information in these files is used by commands such as who(1), last(1),
write(1), or login(1).
