2.9BSD/usr/man/cat5/utmp.5

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UTMP(5)             UNIX Programmer's Manual              UTMP(5)

NAME
     utmp, wtmp - login records

SYNOPSIS
     #include <utmp.h>

DESCRIPTION
     The _u_t_m_p file allows one to discover information about who
     is currently using UNIX.  The file is a sequence of entries
     with the following structure declared in the include file:

          struct utmp {
               char ut_line[8];         /* tty name */
               char ut_name[8];         /* user id */
               long ut_time;            /* time on */
          };

     This structure gives the name of the special file associated
     with the user's terminal, the user's login name, and the
     time of the login in the form of _t_i_m_e(2).

     The _w_t_m_p file records all logins and logouts.  Its format is
     exactly like _u_t_m_p except that a null user name indicates a
     logout on the associated terminal.  Furthermore, the termi-
     nal name `~' indicates that the system was rebooted at the
     indicated time; the adjacent pair of entries with terminal
     names `|' and `{' indicate the system-maintained time just
     before and just after a _d_a_t_e command has changed the
     system's idea of the time.

     _W_t_m_p is maintained by _l_o_g_i_n(1) and _i_n_i_t(8).  Neither of
     these programs creates the file, so if it is removed
     record-keeping is turned off.  It is summarized by _a_c(8).

FILES
     /etc/utmp
     /usr/adm/wtmp

SEE ALSO
     login(1), who(1), init(8), ac(8)

Printed 5/17/83                                                 1