Listing 1: /etc/wtmp file structure

struct utmp
{
char ut_user[8] ;               /* User login name */
char ut_id[4] ;                 /* /etc/lines id(usually line #) */
char ut_line[12] ;              /* device name (console, lnxx) */
short ut_pid ;                  /* process id */
short ut_type ;                 /* type of entry */
struct exit_status
{
short e_termination ;       /* Process termination status */
short e_exit ;              /* Process exit status */
}
ut_exit ;                       /* The exit status of a process
* marked as DEAD_PROCESS.
*/
time_t ut_time ;                /* time entry was made */
} ;