C i cant read binary file properly - c

Question

Hello i have a structure with couple of variables and i try to write and read them from/to binary files but when i read them i see only strange symbols and i dont know what i messed up,i have tried couple of variants but none of them works
typedef struct catalog
{
char num[20];
char name[80];
char author[50];
double price;
int year;
char publisher[80];
} Catalog;
Catalog* createCatalogData()
{
Catalog* c = malloc(sizeof(*c));
if (!c)
{
// Ups... add error handling
exit(0);
}
printf("Add num ");
getString(&c->num);
printf("Add name ");
getString(&c->name);
printf("add author ");
getString(&c->author);
printf("Add price ");
if (scanf("%lf", &c->price) != 1)
{
// Ups... add error handling
exit(0);
}
printf("Add publisher");
getString(&c->publisher);
printf("Add year");
if (scanf("%d", &c->year) != 1)
{
// Ups... add error handling
exit(0);
}
char *filePath = malloc(strlen(c->num) + 13);
char *folderName = "Catalogs\\";
strcpy(filePath, folderName);
strcat(filePath, c->num);
strcat(filePath, ".bin");
FILE *file = fopen(filePath, "wb");
if (file == NULL)
{
printf("Error opening file!\n");
exit(1);
}
fwrite(&c->num,1, strlen(c->num), file);
fwrite(&c->name,1, strlen(c->name), file);
fwrite(&c->author,1, strlen(c->author), file);
fwrite(&c->price, 1, sizeof(double), file);
fwrite(&c->publisher,1, strlen(c->publisher), file);
fwrite(&c->year,1, sizeof(int), file);
fclose(file);
return c;
}
Catalog* readCatalogData(char *filePath)
{
Catalog* c = malloc(sizeof(*c));
FILE* fh;
fopen_s(&fh, filePath, "rb");
//check if file exists
char *ptr;
//read line by line
const size_t line_size = 300;
char* line = malloc(line_size);
int counter = 0;
char* date;
fread(c->num, 1, 21, fh);
fread(c->name, 1, 80, fh);
fread(c->author, 1, 50, fh);
fread(&c->price, 1, sizeof(double), fh);
fread(c->publisher, 1, 80, fh);
fread(c->year, 1, sizeof(int), fh);
return c;
}

Answer 1

When you do e.g.
fwrite(&c->num,1, strlen(c->num), file);
you write a variable number of bytes without any terminator. When you read the file you have no idea how many bytes to actually read.
The above fwrite call actually contains another error, in that you write a pointer and not the actual data in c->num.
Instead of writing the data members one by one, write the whole structure in one single call:
fwrite(c, sizeof c, 1, file);
And when reading the file read the whole structure in a single fread call.
Important note (and as noted by Attie in a comment): If you intend to make this portable, then you should use serialization to read and write the data, as the size of the structure might not be the same on all platforms.
For simple code and just "experimenting" then it will work fine.