ac command prints out a report of connect time (in hours)
based on the logins/logouts in the current
A total is also printed out.
The accounting file
wtmp is maintained by
login. Neither of these programs creates the file; if the
file is not there, no accounting is done. To begin accounting, create
the file with a length of zero. Note that the
wtmp file can get really big, really fast. You might
want to trim it every once and a while.
ac works nearly the same u*x
ac, though it’s a little
smarter in its printing out of daily totals—it actually prints
every day, rather than skipping to the date of the next entry in
All of the original
ac’s options have been implemented, and a few have
been added. Normally, when
ac is invoked, the output looks like
where total is the number of hours of connect time for every entry in
wtmp file. The rest of the flags modify the
output in one way or another.
Print totals for each day rather than just one big total at the end. The output looks like this:
Jul 3 total 1.17 Jul 4 total 2.10 Jul 5 total 8.23 Jul 6 total 2.10 Jul 7 total 0.30
Print time totals for each user in addition to the usual everything-lumped-into-one value. It looks like:
bob 8.06 goff 0.60 maley 7.37 root 0.12 total 16.15
Print out the sum total of the connect time used by all of the users included in people. Note that people is a space separated list of valid user names; wildcards are not allowed.
Read from the file filename instead of the system’s
wtmp file has a problem (a time-warp, missing
record, or whatever), print out an appropriate error.
Reboot records are not written at the time of a reboot, but when
the system restarts; therefore, it is impossible to know exactly
when the reboot occurred. Users may have been logged into the system at
the time of the reboot, and many
ac’s automatically count the
time between the login and the reboot record against the user (even
though all of that time shouldn’t be, perhaps, if the system is
down for a long time, for instance). If you want to count this time,
include the flag. To make
ac behave like the one that
was distributed with your OS, include this flag.
Sometimes a logout record is not written for a specific terminal, so the
time that the last user accrued cannot be calculated. If you want to
include the time from the user’s login to the next login on the terminal
(though probably incorrect), include this flag. To make
ac behave like the one that was distributed with your OS, include
Sometimes, entries in a
wtmp file will suddenly jump
back into the past without a clock change record occurring. It is
impossible to know how long a user was logged in when this occurs. If
you want to count the time between the login and the time warp against
the user, include this flag. To make
ac behave like the
one that was distributed with your OS, include this flag.
This is shorthand for typing out the three above options.
If we’re printing daily totals, print a record for every day instead of skipping intervening days where there is no login activity. Without this flag, time accrued during those intervening days gets listed under the next day where there is login activity.
Print out the year when displaying dates.
If a total for any category (save the grand total) is zero, print it. The default is to suppress printing.
Print verbose internal information.
Set the time warp leniency value (in seconds). Records in
wtmp files might be slightly out of order (most
notably when two logins occur within a one-second period – the second
one gets written first). By default, this value is set to 1 second.
wtmp’s are really screwed up (Suns) and require a
larger value here. If the program notices this problem, time is not
assigned to users unless the
--timewarps flag is used. See the
Problems section for more information.
Set the time warp suspicious value (in seconds). If two records in the
wtmp file are farther than this number of seconds
apart, there is a problem with the wtmp file (or your machine
hasn’t been used in a year). If the program notices this problem, time
is not assigned to users unless the
--timewarps flag is used.
ac’s version number.
ac’s usage string and default locations of system files to
For no fault of
ac’s, if two logins occur at the same time
(within a second of each other), each
login process will try to
write an entry to the
wtmp file. With file system
overhead, it is forseeable that the entries would get written in the
wrong order. GNU
ac automatically compensates for this, but some
acs may not... beware.
I’ve tested the standard
ac in Ultrix 4.2 (DECstation/DECsystem),
SunOS 4.1.1 (Sun3, Sun4, Sparc), Mach 2.5 (Omron/Luna), and DomainOS
10.3 (DN3500). All of these
acs have trouble parsing entries in
which the line is
ftpxxxx (xxxx being some number).
acs see one of these entries, they log everyone
out at the time of the entry.
HOW IT HAPPENS: if there is a user logged into the machine when an ftp connection occurs, (minimally) you’ll get a login record for the user, a login record for the ftp connection, and the logouts for both afterwards (in either order).
TANGIBLE RESULT: the user who was logged in gets ’logged out’
at the time the ftp connection begins, and none of the time spent during
or after the ftp connection. Therefore, when you run GNU
the totals will most likely be greater than those of your system’s
ac (provided you specify the other flags that will make GNU
ac behave like the system’s).
init is a little screwed up. For some reason, after a
shutdown record is written, a reboot record is written with a time-stamp
before the shutdown (less than 30 seconds, usually).
TANGIBLE RESULT: GNU
ac will notice the problem, log
everyone out (you can specify if you want the time to be added to the
user’s total) and begin a new day entry based on the time of the
out-of-sync record. If you try to print out daily totals, you’ll notice
that some days might have two or more entries.
SOLUTION: To fix this, a timewarp leniency value has been implemented. If any record is out of order by this number of seconds (defaults to 60) it gets ignored. If you need to change this value (if you think the totals are off because the value is too high), you can change it using the ‘--timewarp-value’ flag. The rationale for the 60 second default is that of all of the machines with this problem, the largest timewarp was 45.
ac’s on System V machines (I’ve tried SGI Indigo & SGI Indy)
forget to pay attention to the
ut_type field in a
utmp. As such, they chalk up a lot of time to non-existant processes
TANGIBLE RESULT: The amount of total time reported by the
ac is really off. Often, it’s several times
greater than what it should be.
ac always pays attention to the
ut_type record, so there’s no possibility of chalking up time to
anything but user processes.