// $Id: getblock.c,v 1.1 2004-12-09 01:40:59+09 kaiya Exp kaiya $

/*
Spec
   Get nth block from a file

Usage
   ./a.out block_number < filesystem_file > output_file

Limit
   block_number: natural number
   0<=block_number<1440
   filesytem_file should be simple ext2 file system dump; 
   i.e. block size=1024B, number of blocks=1440.

Comple
   gcc thisfile.c
 */

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

// #include <linux/ext2_fs.h>

#define BLOCKSIZE 1024

main(int argc, char* argv[]){
unsigned char block[BLOCKSIZE];
int nb, c;

	if(argc<2) exit(1);
	nb=atoi(argv[1]);
	if(nb<0 || nb>1440) exit(2);

	fprintf(stderr, "get block #\%d\n", nb);

	for(c=0; read(0, block, BLOCKSIZE)==BLOCKSIZE; c++){
		if(c==nb){
			write(1, block, BLOCKSIZE);
			break;
		}
	}
}