Product

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define NAME (20)
#define SPEC (50)
typedef struct {
  int id;
  char name[NAME], spec[SPEC];
  int price, items;
} product_t;
typedef struct {
  int id;
  char name[NAME], spec[SPEC];
  int price;
} item_t;
typedef struct {
  int id, items;
} order_t;
static product_t *add_product(int id, char *name, char *spec, int price, int items) {
  product_t *new = (product_t *) malloc(sizeof(product_t));
  new->id = id;
  strcpy(new->name, name);
  strcpy(new->spec, spec);
  new->price = price;
  new->items = items;
  return new;
}
static product_t **read(FILE *in, int *order) {
  char line[BUFSIZ], *tok;
  int c, id, price, items;
  char name[NAME], spec[SPEC];
  product_t **all_product = NULL;
  *order = 0;
  while (fgets(line, BUFSIZ, in)) {
    for (c = 0, tok = strtok(line, ","); tok && *tok; c++, tok = strtok(NULL, ",\n")) {
      if (c == 0) {
        id = atoi(tok);
        continue;
      }
      if (c == 1) {
        strcpy(name, tok);
        continue;
      }
      if (c == 2) {
        strcpy(spec, tok);
        continue;
      }
      if (c == 3) {
        price = atoi(tok);
        continue;
      }
      if (c == 4) {
        items = atoi(tok);
        break;
      }
    }
    (*order)++;
    all_product = (product_t **) realloc(all_product, *order * sizeof(product_t *));
    all_product[*order - 1] = add_product(id, name, spec, price, items);
  }
  return all_product;
}
static order_t **extract_order(product_t **all_product, int order) {
  int i;
  order_t **all_order = (order_t **) malloc(order * sizeof(order_t *));
  for (i = 0; i < order; i++) {
    all_order[i] = (order_t *) malloc(sizeof(order_t));
    all_order[i]->id = all_product[i]->id;
    all_order[i]->items = all_product[i]->items;
  }
  return all_order;
}
static item_t *find_id_from_item(item_t **all_item, int id, int ids) {
  int i;
  for (i = 0; i < ids; i++) {
    if (all_item[i]->id == id) return all_item[i];
  }
  return NULL;
}
static item_t *add_item(int id, char *name, char *spec, int price) {
  item_t *new = (item_t *) malloc(sizeof(item_t));
  new->id = id;
  strcpy(new->name, name);
  strcpy(new->spec, spec);
  new->price = price;
  return new;
}
static item_t **extract_item(product_t **all_product, int order, int *ids) {
  int i;
  product_t *p;
  item_t **all_item = NULL;
  *ids = 0;
  for (i = 0; i < order; i++) {
    p = all_product[i];
    if (!find_id_from_item(all_item, p->id, *ids)) {
      (*ids)++;
      all_item = (item_t **) realloc(all_item, *ids * sizeof(item_t *));
      all_item[*ids - 1] = add_item(p->id, p->name, p->spec, p->price);
    }
  }
  return all_item;
}
static void puts_item_number(FILE *out, int ids) {
  fprintf(out, "===商品数===\n%d\n", ids);
}
static void puts_total_per_item(FILE *out, item_t **all_item, order_t **all_order, int order, int ids, int *all_total) {
  int i, j, total, id;
  *all_total = 0;
  fprintf(out, "\n===商品ごとの合計===\n");
  for (i = 0; i < ids; i++) {
    id = all_item[i]->id;
    for (total = 0, j = 0; j < order; j++)
      if (id == all_order[j]->id) total += all_item[i]->price * all_order[j]->items;
    fprintf(out, "%s,%d\n", all_item[i]->name, total);
    *all_total += total;
  }
}
static void puts_all_total(FILE *out, int all_total) {
  fprintf(out, "\n===全商品の合計===\n%d\n", all_total);
}
int main(int argc, char **argv) {
  FILE *in, *out;
  product_t **all_product = NULL;
  item_t **all_item = NULL;
  order_t **all_order = NULL;
  int order, ids, all_total;
  in = fopen(argv[1], "r");
  all_product = read(in, &order);
  fclose(in);
  all_order = extract_order(all_product, order);
  all_item = extract_item(all_product, order, &ids);
  out = fopen(argv[2], "w");
//  out = stdout;
  puts_item_number(out, ids);
  puts_total_per_item(out, all_item, all_order, order, ids, &all_total);
  puts_all_total(out, all_total);
  fclose(out);
  return 0;
}