reading structure data I\'m done writing a code but can\'t figured out the solut

Question

reading structure data

I'm done writing a code but can't figured out the solution for error. I think it's quite simple fix.

I have 3 files
grades.txt // contains 8 grades
grades.h // structure
grades.c // main

Here are the description of the program is asking

1. Accepting two arguments, 1 for filename grades.txt, and 1 for user ID (ex.123)
2. Display the grades and those average, until I have all 8 grades or met the negative grades
3. Convert user ID into a number uid
4. Read the structure starting at offset (uid*sizeof(struct GR))

**grades.h**
#ifndef GRADE
#define GRADE
  
struct GR {
   float gr[8];
};
#endif

**grades.c**
#include
#include
#include "grades.h"
  
int main(int argc, char *argv[]) {
   struct GR *grades = malloc(sizeof(struct GR));
   FILE *file = fopen(argv[1], "rb");

     // convert character uid into integer uid
   char *chUid = argv[2];
   int uid = 0;
   int len = strlen(chUid);

   for (int i = 0; i < len; i++) {
       uid = uid * 10 + (chUid[i] - '0');
   }
   printf("Converted uid: %d ", uid);
  
   fread(grades, uid * sizeof(struct GR), 1, file);
  
   float total = 0, avg = 0;
   int i = 0;
   while (i < 9 && grades->gr[i] > 0) {
       printf("%d ", grades->gr[i]);
       total += grades->gr[i];
       i++;
   }
   printf("Average: %d ", total / i);    
   return 0;
}

I'm stuck on fread method.. struct is not having any value

Explanation / Answer

Why are u redefining 'i' variable before while loop. Just write "i=0;" instead of "int i=0;"

Also after main, write like this:

struct GR *grades;

grades = (struct GR *) malloc(sizeof(struct GR));

See if this works

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