Only do accounting logins on certain ttys. The tty specification can start with ! to indicate not this tty and end with * to indicate all similarly named ttys. Multiple -t flags may be specified.
Read connect time data from wtmp instead of the default file, /var/log/wtmp.
Display totals for the given individuals only.
If no arguments are given, ac displays the total connect time for all accounts with login sessions recorded in wtmp.
The default wtmp file will increase without bound unless it is truncated. It is normally truncated by the daily scripts run by cron(8), which rename and rotate the wtmp files, keeping a weeks worth of data on hand. No login or connect time accounting is performed if /var/log/wtmp does not exist.
ac -p -t "ttyd*" > modems
ac -p -t "!ttyd*" > other
allows times recorded in modems to be charged out at a different rate than other.