How can I read struct elements from file? - c

Question

Hi I have the following structure:
struct points{
int round[11];
int sum;
};
struct student{
char studid[7];
char *s_name;
char *f_name;
struct points p_points;
};
I am creating an array of structures, each representing an individual student. When I exit my program I will save that array to a file using the following function:
int save_file(struct student *array, int size, const char *filename){
struct student *object=malloc(size*sizeof(struct student));
for(int i=0;i<size;i++){
object[i].f_name=malloc(strlen(array[0].etunimi)+1);
object[i].s_name=malloc(strlen(array[0].sukunimi+1));
strcpy(object[i].f_name,array[0].etunimi);
strcpy(object[i].s_name,array[0].sukunimi);
strcpy(object[i].studid,array[0].opnro);
object[i].points=array[0].points;
}
FILE * file= fopen(filename, "wb");
if (file != NULL) {
fwrite(object, size*sizeof(struct student), 1, file);
fclose(file);
}
for(int x=0;x<size;x++){
free(object[x].etunimi);
free(object[x].sukunimi);
}
free(object);
return 1;
}
When I want to modify the record and load the file I am facing a problem. I don't know how to allocate memory for object[i].f_name and object[i].s_name and I don't know the size of the array in the file. My function looks like this now:
int read_file(const char *filename){
struct student *object2=malloc(sizeof(struct student));
FILE * file= fopen("output", "rb");
if (file != NULL) {
fread(object2, sizeof(struct student), 1, file);
fclose(file);
}
print_situation(object2,1);
return 1;
}
How can I check the size of the array in the file and get the lengths of f_name and s_name from the file in order to allocate the memory properly?