#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>

int main(int argc, char *argv[]){
	if (argc != 3){
		fprintf(stderr, "%c <file_name> <offset>", argv[0]);
		exit(1);
	}
	off_t offset;
	ssize_t nb_read;
	int nb, n;
	int fdin;
	fdin = open(argv[1], O_RDONLY);
	if (fdin == -1){
		perror("File can't be opened");
		exit(2);
	}
	offset = (off_t) strtol (argv[2], NULL, 0);
	n = lseek(fdin, offset * sizeof(int), SEEK_SET);
	if (!n){
		perror("Offset is out of range!");
		exit(3);
	}
	nb_read=read(fdin, &nb, sizeof(int));
	if (nb_read < 0){
		perror("File can't be read");
		exit(4);
	}
	printf("The number at offset %s is %x --> %d\n", argv[2], nb, nb);
	return EXIT_SUCCESS;
}