UTMP(5)                          File Formats                          UTMP(5)


       utmp, wtmp, lastlog - login records


       #include <utmp.h>


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

       These files can grow rapidly on busy systems, daily or weekly  rotation
       is recommended.  If any of these files do not exist, it is not created.
       These files must be created manually and  are  normally  maintained  in
       either the script /etc/daily or the script /etc/weekly.  (See cron(8).)

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

       #define UT_NAMESIZE     8
       #define UT_LINESIZE     8
       #define UT_HOSTSIZE     16

       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];
               long    ut_time;

       Each time a user logs in, the login program looks up the user's UID  in
       the  file  lastlog.  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. (Providing the login is not quiet, see login(1).)  The
       login program then records the new login time in the file lastlog.

       After the new lastlog record is written, the file utmp  is  opened  and
       the utmp record for the user inserted.  This record remains there 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  program  opens the file wtmp, and appends the user's
       utmp record.  The same utmp record, with an updated time stamp is later
       appended  to  the file when the user logs out. (See init(8).)  The wtmp
       file is used by the programs last(1) and ac(8).

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

              reboot, shutdown
                     A  system  reboot  or  shutdown  has been initiated.  The
                     character ~ is placed in the field ut_line, and reboot or
                     shutdown  in  the  field  ut_name.   (See shutdown(8) and

              date   The  system  time  has  been  manually  or  automatically
                     updated.   (See  date(1).)   The  command  name  date  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.


                     The utmpfile.

                     The wtmpfile.

                     The lastlogfile.


       This man page is not quite right for the GNO implementation (the struc-
       tures are incorrect, as is the utmp path).


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


       A utmp and wtmp file format appeared in Version 6 AT&T UNIX.  The last-
       log file format appeared in 3.0BSD.

GNO                            17 September 1997                       UTMP(5)

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