Entry in a user-information file
#include <utmp.h>
struct utmp {
    char    ut_user[UT_NAMESIZE];
#define ut_name ut_user
    char    ut_id[4];
    char    ut_line[UT_LINESIZE];
    pid_t   ut_pid;
    short   ut_type;
    struct exit_status {
        short   e_termination;
        short   e_exit;
    } ut_exit;
    short   ut_spare;
    time_t  ut_time;
};
The utmp structure describes an entry in a user-information file. The members include: