Someone

#include <stdio.h>
#include <sys/types.h>
#include <strings.h>
#include <string.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <utmp.h>

#define WHO "LOGIN"



main() {
  struct utmp utmp_ent;
  FILE *fp;

  fp = fopen(UTMP_FILENAME, "rb");  
//  fp = fopen(WTMP_FILENAME, "rb");
 
  if(fp) { 
//    while(!feof(fp)) {

    while(fread(&utmp_ent, sizeof(utmp_ent), 1, fp)) {
      if(!strncmp(utmp_ent.ut_name, WHO, strlen(WHO))) {
        bzero((char *)&utmp_ent, sizeof(utmp_ent));
//        fseek(fp, -(strlen(WHO)), SEEK_CUR);
//        printf("%s\n", utmp_ent.ut_name);
      }
      printf("%s\n", utmp_ent.ut_name);
//      fclose(fp);
    }
  }
}