ac - login accounting
ac [ -w wtmp ] [ -p ] [ -d ] [ people ] ...
Ac produces a printout giving connect time for each user who has logged
in during the life of the current wtmp file. A total is also produced.
-w is used to specify an alternate wtmp file. -p prints individual
totals; without this option, only totals are printed. -d causes a
printout for each midnight to midnight period. Any people will limit
the printout to only the specified login names. If no wtmp file is
given, /usr/adm/wtmp is used.
The accounting file /usr/adm/wtmp is maintained by init and login.
Neither of these programs creates the file, so if it does not exist no
connect-time accounting is done. To start accounting, it should be
created with length 0. On the other hand if the file is left undis‐
turbed it will grow without bound, so periodically any information
desired should be collected and the file truncated.
init(8), login(1), utmp(5).