#include<stdio.h>
#include<stdlib.h>
#include<time.h>
 
int fun_compare (const void * el1, const void * el2){
  double diff;

  diff =  *(double*)el1 - *(double*)el2 ;
  if ( diff > (double)0.0 ) return 1;
  if ( diff < (double)0.0 ) return -1;
  return 0;
}

int main (){   /* x-ordinamento.c */
  int i;
  FILE* numb;
  const int dim=10;
  double array[10];
  double el1, el2;
  clock_t t0, t1;
  double t_sort, t_qsort;

  for(i=0; i<dim; i++){
     array[i] = (double)rand()/(double)100000000;
  }
  t0 = clock();
  numb = fopen("numbers.txt","w");
  if ( numb == NULL ) {
     fprintf(stderr,"Error opening 'numbers.txt' file for writing\n");
     return(-1);
  }
  for (i=0; i<dim; i++){
    fprintf (numb,"%8.3f\n",array[i]);
  }
  fclose(numb);
  i = system("sort -g numbers.txt");
  if ( i != 0 ) {
     fprintf(stderr,"Error calling sort\n");
     return(-1);
  }
  t1 = clock();
  t_sort = (double)(t1-t0)/(double)CLOCKS_PER_SEC;
  
  t0 = clock();
  qsort(array, (size_t)dim, (size_t)sizeof(double), fun_compare);
  t1 = clock();
  t_qsort = (double)(t1-t0)/(double)CLOCKS_PER_SEC;

  printf("Sorted sequence should be:\n");
  for (i=0; i<dim; i++){
    printf ("%8.3f ",array[i]);
  }  printf ("\n");
  
  printf("\nSecondi per l'ordinamento di numbers.txt: %lf\n",t_sort);
  printf("\nSecondi per l'ordinamento dell'array: %lf\n",t_qsort);

  return(0);
}