当调用FREAD()函数时，文件指针如何移动

Question

//Libraries are called accordingly 
struct std    
{
int a;
char b;
}// a structure with 2 objects
void main()
{
std h[5]; // structure array with 5 elements
int rec_size; // Size of single record to be accessed from the file 
rec_size=sizeof(structure std); // stores the size in bytes
while (true) 
  {
     fread(&h,rec_size,2,fptr); //fptr is a file pointer to some file
    /*Assume that the file pointer(fptr)has covered the last two record 
      blocks and stored
      them in "h". Then the shouldn't the position pointer proceed to end of 
      file and the next statement "if(feof(fptr)" then becomes true to exit 
      the loop and in essence miss out on the processing of those last two 
      record blocks?*/
    if(feof(fptr)) 
     /* Here, if the fptr has reached the end of file after fread(), 
        then this should execute*/                           
      break;
   //else additional code to process the content stored in "h" 
  }
}

我的疑问是，当Fread((函数返回并且在下一个语句FEOF((检查EOF时，如果Fread((处理了文件中的最后两个记录块，feof((是否返回true？有人可以完全解释功能吗？

Answer 1

feof()用于知道您命中了哪种错误，而不是检测到一个错误。正确的方法是检查文件末尾的fread()的有价值的回报。然后，如果feof()为真，您知道您已经到达EOF，否则会有一个错误。

因此，使用当前代码，您正在处理最后可读记录的两倍。另外，您的意思是&h[0]，而不是&h。