#include <stdio.h>
#include <stdlib.h>
#include <utmp.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <pwd.h>

#define UTMP "/var/run/utmp"

int main(void) {
  int i, fd;
  struct utmp *ue;
  struct stat s;

  stat(UTMP, &s);
  ue = malloc(s.st_size);
  fd = open(UTMP, O_RDONLY);
  read(fd, ue, s.st_size);
  close(fd);

  printf("%-10s%-7sHOSTNAME\n", "USER", "TTY");
  for (i=0; i<s.st_size/sizeof(struct utmp); i++)
    if (getpwnam(ue[i].ut_user)) printf("%-10s%-7s%s\n", ue[i].ut_user,
	ue[i].ut_line, (ue[i].ut_host[0] != 0) ? ue[i].ut_host : "localhost");

  return 0;
}