NAME

     utmp, wtmp - logged in users, login and logout history


SYNOPSIS

     #include <sys/types.h>
     #include <utmp.h>


DESCRIPTION

     The files /etc/utmp and /usr/adm/wtmp  respectively  contain
     the currently logged in users, and the history of logins and
     logouts.

     Each file is an array of the following structure defined  in
     <utmp.h>:

     struct utmp {
          char           ut_user[8];    /* user name */
          char           ut_line[12];   /* terminal name */
          char           ut_host[16];   /* host name, when remote */
          time_t         ut_time;       /* login/logout time */
     };

     #define ut_name ut_user/* for compatibility with other systems */

     The structure contains more fields than  those  listed,  but
     they  are only of interest to init and login.  Note that the
     ut_name field is a compatibility alias for  ut_user,  it  is
     actually better to use it.

     A login entry is completely specified.  A logout entry has a
     null  string for ut_name.  A shutdown or reboot entry has an
     ut_line field containing a "~" (tilde).  The  ut_name  field
     is usually the name of the program that did the shutdown, or
     "reboot" at reboot.  This is a bit confusing, but note  that
     there  should  always  be two such entries.  If you see just
     one entry then the  system  has  crashed,  if  you  see  two
     entries  then  the  system  was properly shut down and later
     rebooted.


FILES

     /etc/utmp                Currently logged in users.

     /usr/adm/wtmp            History of logins and logouts.


SEE ALSO

     who(1), ttyslot(3).


AUTHOR

     Kees J. Bot (kjb@cs.vu.nl)