存储到我的文件中的结构没有被覆盖（C）

Question

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

typedef struct batch
{
  int month;
  int day;
  int qty;
  float item_cost;
  int batch_num;
} BATCH;

struct stock
{
  char item_name[50];
  int t_qty;
  float t_item_cost;
  int item_code;
  BATCH batch[10];
  int last_batch_num;
  float price_for_one;
  float price;
};

int main()
{
   FILE *filepointer;
   filepointer = fopen("stocklist.txt", "r+");

   struct stock loop;

   while(fread(&loop, sizeof(struct stock), 1, filepointer))
   {
       printf("%s\n", loop.item_name);
       strcpy(loop.item_name, "Jerb");
       printf("%s\n", loop.item_name);

       fwrite(&loop, sizeof(struct stock), 1, filepointer);
    }
}

There is a text file which has in an item_name which is Huggies, so every time I run the program it should change the name of Huggies to "Jerb" but it seems that it isn't having any effect on the file and the old item_name stays in the same in the file.

I would have thought that if I used the "r+" mode it would overwrite this data in the file but it isn't.

Help please!!

Answer 1

Try doing fflush() inside the loop and fclose before exiting. When fwrite() is called, the output is written to a buffer until 4kb of data is generated and flushed to the file only when it reaches 4kb or when fflush/fclose is called.