The `ac' command prints out a report of connect time (in hours)
based on the logins/logouts in the current `wtmp' file. A total is
also printed out.
The accounting file `wtmp' is maintained by `init' and `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. really
fast. You might want to trim it every once and a while.
GNU `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 the `wtmp'
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
the `wtmp' file. The rest of the flags modify the output in one way or
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:
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.
When the `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 this flag.*
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
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. Some `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.
Print `ac''s version number.
Print `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 other `ac's may not...
The FTP Problem
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 `ac's have trouble parsing entries in
which the line is `ftp'XXXX (XXXX being some number). Whenever these
`ac's see one of these entries, they log everyone out at the time of
*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 `ac', 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
The Shutdown/Reboot Problem
On Suns, `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.
Stupid System V Machines
Some `ac''s on System V machines (I've tried SGI Indigo & SGI Indy)
forget to pay attention to the `ut_type' field in a `struct utmp'. As
such, they chalk up a lot of time to non-existant processes called
`LOGIN' or `runlevel'.
*TANGIBLE RESULT:* The amount of total time reported by the system's
`ac' is *really* off. Often, it's several times greater than what it
*SOLUTION:* GNU `ac' always pays attention to the `ut_type' record, so
there's no possibility of chalking up time to anything but user
automatically generated by