#include <stdio.h>
#include <stdlib.h>
#include <math.h>

FILE * OpenFile(char * filename, char * mode) {
/*  Generic Open File function with error checking */
  FILE *fp;

  if ((fp=fopen(filename,mode))==NULL) {
    printf("Cannot open file %s\n",filename);
    exit(1);
  }
  return fp;
}

int main (int argc, char *argv[]) {
/* If Initial Filter Coefficient flag (-f) is set, filter coeffs.  */
/* are preset to LAST values of filter file.  This file will be    */
/* overwritten during excution of code.                            */

  FILE *fpin, *fpout;
  int i=0;
  short int hd_data=0;
  
  fpin = OpenFile (argv[1], "rb");
  fpout = OpenFile (argv[2], "wb");
  fseek (fpin, -2*atol(argv[3]), SEEK_END);
  while(i<atoi(argv[3])) {
    if (fread(&hd_data, sizeof(short int), 1, fpin) != 1) {
      printf("Read Error in input\n");
      fclose(fpin);
      exit(1);
    }
    if (fwrite(&hd_data, sizeof(short int), 1, fpout) != 1) {
      printf ("Read Error in output\n");
      exit(1);
    }
    printf("%d\n",hd_data);
    i++;
  }
  fclose(fpin);
  fclose(fpout);
}