/* Write and read a binary file (fwrite and fread) */

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

#define LEN 50
#define N_STUD 2

typedef struct stud{
  char name[LEN+1];
  unsigned int id;
  float average;
}stud_t;


int main() {
  FILE *fp;
  stud_t student[N_STUD];
  int i;
  char row[LEN+1];
  unsigned int n_stud;

  strcpy(student[0].name, "Steven");
  student[0].id = 120000;
  student[0].average = 25.5;

  strcpy(student[1].name, "Julia");
  student[1].id = 120001;
  student[1].average = 28.5;

  fp = fopen("out.bin", "w"); /* Open the file for writing */
  if (fp == NULL){
    printf("Error: file out.bin cannot be opened\n");
    exit(1);
  }


  /* Write the file */
  /* NOTE 2: a binary file sometimes cannot be readable 
     correctly in a PC that it is not the one which generates it, 
     because, for instance, integer numbers can be coded with a
     different number of bytes.
  */
 
  /* Write in binary all the data contained in the structure */
  fwrite(student, sizeof(stud_t), N_STUD, fp); 

  /* DIMENSION OF THE GENERATED FILE
     The dimension of the generated file will be:
     n_stud*sizeof(stud_t)
     in the case of the computer used to test the program:
     2*60 = 120 byte
   */
  
  fclose(fp); /* Close the file */


  
  fp = fopen("out.bin", "r"); /* Open the file for reading */
  if (fp == NULL){
    printf("Error: file out.bin cannot be opened\n");
    exit(1);
  }

  /* Read the file */
  n_stud = 0;
  while( fread(&student[n_stud], sizeof(stud_t), 1, fp) == 1 ) {
    n_stud++;
  }

  fclose(fp); /* Close the file */

  
  /* Print the read records */
  for (i=0; i<n_stud; i++) {
    printf("%s %d %f\n", student[i].name, student[i].id, student[i].average);
  }


  return 0;
}