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 */
  } ;
