如何使用c读取n记录的二进制文件答案

【问题标题】：How do I read a binary file of n record using c如何使用c读取n记录的二进制文件
【发布时间】：2021-12-20 02:27:18
【问题描述】：

我有一个将 n 条配置文件记录写入二进制文件的代码，但是当我尝试从中读取并在控制台上打印时，它不起作用并进入无限循环，这是我的代码：

/*profile strucre */
struct profile 
{
  char name[30];
  int phoneNumber;
} pr;


int main()
{
   int rn; 
   FILE *fp; //le fichier
   printf("\nHow many profiles would you like to have?");
   scanf("%d", &rn);
   struct profile p[rn];
   for (int i = 0; i < rn; i++)
 {
 printf("\nEnter the name no %d: ", i+1);
 scanf("%s", p[i].name);
 printf("\nEnter the name phone number %d: ", i+1);
 scanf("%d", &p[i].phoneNumber);
 }

 //file creation 
 for (int i = 0; i < rn; i++)
 {
  fp = fopen ("profiles.bin", "wb");
  if (fp != NULL)
  {
    fwrite (&p[i], sizeof (p[i]), 1, fp);
    fclose (fp);
  }
 }

/* file reading */
    if(fp==NULL) //if the file doesnt existe
    {
        printf("File could not open");
        exit(0); //EXIT SUCCESS
    }
    int j = 1;
    while((fread(&pr,sizeof(pr),1,fp)!= EOF)) //this doesnt work
    {
      printf("\nRecord No:%d",j);
      printf("\n------------------");
      printf("\nName:%s",pr.name);
      printf("\nPhone number:%d",pr.phoneNumber);
      printf("\n=======================");
      j++;
    }
    fclose(fp);
    
}

输出是：

=======================
Record No:3728
------------------
Name:
Phone number:0
=======================
Record No:3729
------------------
Name:
Phone number:0
=======================
Record No:3730
------------------
Name:
Phone number:0
=======================
Record No:3731
------------------
Name:
Phone number:0
=======================
Record No:3732
------------------
Name:
Phone number:0
=======================
Record No:3733
------------------
Name:
Phone number:0
=======================
Record No:3734
------------------
Name:
Phone number:0
=======================
Record No:3735
------------------
Name:
Phone number:0
=======================
Record No:3736
------------------
Name:
Phone number:0
=======================
Record No:3737
------------------
Name:
Phone number:0
=======================
Record No:3738
------------------
Name:
Phone number:0
=======================
Record No:3739
------------------
Name:
Phone number:0
=======================
Record No:3740
------------------
Name:
Phone number:0
=======================
Record No:3741
------------------
Name:
Phone number:0
=======================
Record No:3742
------------------
Name:
Phone number:0
=======================
Record No:3743
------------------
Name:
Phone number:0
=======================
Record No:3744
------------------
Name:
Phone number:0
=======================
Record No:3745
------------------
Name:
Phone number:0
=======================
Record No:3746
------------------
Name:
Phone number:0
=======================
Record No:3747
------------------
Name:
Phone number:0
=======================
Record No:3748
------------------
Name:
Phone number:0
=======================
Record No:3749
------------------
Name:
Phone number:0
=======================
Record No:3750
------------------
Name:
Phone number:0
=======================
Record No:3751
------------------
Name:
Phone number:0
=======================
Record No:3752
------------------
Name:
Phone number:0
=======================
Record No:3753
------------------
Name:
Phone number:0
=======================
Record No:3754
------------------
Name:
Phone number:0

【问题讨论】：

寻求调试帮助的问题必须提供完整的代码minimal reproducible example。请使用完整的代码更新问题，任何人都可以完全按照所示运行以重现问题。
不要省略重要的代码，例如您如何打开文件以及如何检查错误。
文件创建错误，因为每次迭代都会打开和关闭文件。这意味着它每次都会覆盖文件的开头。那么读取也是错误的，因为它没有打开文件。
查看fread() 的手册页。可以返回EOF 吗？

标签： c file binaryfiles

【解决方案1】：

  fp = fopen ("profiles.bin", "wb");
  if (fp != NULL)
  {
    fwrite (&p[i], sizeof (p[i]), 1, fp);
    fclose (fp);
  }

您每次都关闭并覆盖您的文件。所以你那里只有一条记录。

您需要将关闭移出循环。

  fp = fopen ("profiles.bin", "wb");
  if (fp != NULL)
  {
    fwrite (&p[i], sizeof (p[i]), 1, fp); 
    // add some error checking
  }
  fclose (fp);

您还需要打开文件进行阅读（因为它已关闭）

  fp = fopen ("profiles.bin", "rb");
/* file reading */
    if(fp==NULL) //if the file doesnt exist

【讨论】：

我现在得到一个输出，但它只是最后一条记录，它仍在无限循环中