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

struct date
{ short int year;
  unsigned char month, day; };

struct record
{ struct date when;
  float minT, avgT, maxT;
  unsigned char snow, prec;
  float wind; };

void print(struct record r)
{ printf("%d-%d-%d %f %f %f %d %d %f\n", 
         r.when.year, r.when.month, r.when.day,
         r.minT, r.avgT, r.maxT, r.snow, r.prec, r.wind); }

int compare(struct date w, int y, int m, int d)
{ if (w.year != y)
    return w.year - y;
  if (w.month != m)
    return w.month - m;
  if (w.day != d)
    return w.day - d;
  return 0; }

int main()
{ int fin = open("weather.dat", O_RDONLY);
  int y, m, d;
  int first, last;
  if (fin < 0)
  { fprintf(stderr, "Can't open file\n");
    exit(1); }
  printf("Enter y m d: ");
  scanf("%d %d %d", &y, &m, &d);
  first = 0;
  last = lseek(fin, 0, SEEK_END) / sizeof(struct record) - 1;
  while (1)
  { int middle = (first+last)/2;
    struct record r;
    int c;
    printf("first=%d, middle=%d, last=%d\n", first, middle, last);
    lseek(fin, middle * sizeof(r), SEEK_SET);
    read(fin, &r, sizeof(r));
    printf("compare ");
    print(r);
    printf(" with %d %d %d\n", y, m, d);
    c = compare(r.when, y, m, d);
    if (c == 0)
    { printf("found it:\n");
      print(r);
      break; }
    else if (c < 0)
      first = middle + 1;
    else
      last = middle - 1; }
  close(fin); }