NAME    [Toc]    [Back]

     utmp, wtmp, lastlog - login records

SYNOPSIS    [Toc]    [Back]

     #include <utmp.h>

DESCRIPTION    [Toc]    [Back]

     The <utmp.h> file declares the structures used to record information
     about  current users in the utmp file, logins and logouts in
the wtmp
     file, and last logins in the lastlog file.   The  timestamps
of date
     changes,  shutdowns, and reboots are also logged in the wtmp
file.

     wtmp can grow rapidly on busy systems, so  daily  or  weekly
rotation is
     recommended.   If  any one of these files does not exist, it
is not created.
  They must be created manually  and  are  maintained  by
newsyslog(8).

           #define _PATH_UTMP      "/var/run/utmp"
           #define _PATH_WTMP      "/var/log/wtmp"
           #define _PATH_LASTLOG   "/var/log/lastlog"

           #define UT_NAMESIZE     32
           #define UT_LINESIZE     8
           #define UT_HOSTSIZE     256

           struct lastlog {
                   time_t  ll_time;
                   char    ll_line[UT_LINESIZE];
                   char    ll_host[UT_HOSTSIZE];
           };

           struct utmp {
                   char    ut_line[UT_LINESIZE];
                   char    ut_name[UT_NAMESIZE];
                   char    ut_host[UT_HOSTSIZE];
                   time_t  ut_time;
           };

     Each  time a user logs in, the login(1) program looks up the
user's UID in
     the lastlog file.  If it is found, the timestamp of the last
time the user
  logged in, the terminal line, and the hostname are written to the
     standard output (provided the login is  not  ``quiet'';  see
login(1)).  The
     login(1)  program  then  records  the  new login time in the
lastlog file.

     After the new lastlog record is written, the  utmp  file  is
opened and the
     utmp  record  for the user is inserted.  This record remains
until the user
     logs out at which time it is deleted.  The utmp file is used
by the programs
 rwho(1), users(1), w(1), and who(1).

     Next,  the  login(1) program opens the wtmp file and appends
the user's
     utmp record.  When the user logs out, a utmp record with the
tty line, an
     updated  timestamp,  and  zeroed name and host fields is appended to the
     file (see init(8)).  The wtmp file is used by  the  programs
last(1) and
     ac(8).

     In the event of a date change, shutdown, or reboot, the following items
     are logged in the wtmp file:

     reboot
     shutdown    A system reboot or shutdown has been  initiated.
A tilde
                 (`~')  character is placed in the field ut_line,
and
                 ``reboot'' or ``shutdown'' in the field  ut_name
(see
                 shutdown(8) and reboot(8)).

     date         The  system time has been manually or automatically updated
                 (see date(1)).   The  command  name  date(1)  is
recorded in the
                 field  ut_name.  In the field ut_line, the ``|''
character indicates
 the time prior to  the  change  and  the
``{'' character
                 indicates the new time.

FILES    [Toc]    [Back]

     /var/run/utmp
     /var/log/wtmp
     /var/log/lastlog

SEE ALSO    [Toc]    [Back]

     last(1), login(1), who(1), ac(8), init(8), newsyslog(8)

HISTORY    [Toc]    [Back]

     A utmp and wtmp file format appeared in Version 3 AT&T UNIX.
The lastlog
     file format appeared in 3.0BSD.

CAVEATS    [Toc]    [Back]

     The strings in the utmp and lastlog structures are not  normal `C' strings
     and are thus not guaranteed to be null terminated.

OpenBSD      3.6                          March      17,     1994