#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>
#define STDOUT 1
#define STDERR 2
#define SZBUF 256


int main(int argc, char** argv){
  int descripteur, curseur, nb;
  long int offset, i;
  char buf[SZBUF];
  
  if (argc < 2){
    fprintf(stderr, "Usage : %s <file-name>\n",argv[0]);
    exit(1);
  }
  descripteur = open(argv[1], O_RDONLY);
  if (descripteur==-1){
    perror("opening file fail !");
    exit(2);
  }
  i = strtol(argv[2],NULL,0);
  offset = i*4;
  curseur = lseek(descripteur, offset, SEEK_SET);
  if (curseur == -1){
    perror("lseek fail");
    exit(3);
  }
  nb = read(descripteur,&x,4);
  if (nb == -1){
    perror("Read in file fail");
    exit(4);
  }
  if (nb == 0){
    perror("out of range");
    exit(5);
  }
  printf("The number at offset %d is 0x%08x --> %d\n",i,x,x);
  exit(0);
}