Сохранение и считывание с бинарного файла

Мне нужно чтобы все записывалось в бинарный файл (предусмотреть, если его нет, и тогда сказать что база данных пуста). Тоесть, чтобы при первом запуске бд была пустая, человек заполнил структуру, она сохранилась в бинарный файл и при следуюзем запуске, когда человек захочет посмотреть список студентов он увидит данные о том студенте, данные о котором вводил в прошлый раз. Не пойму то-ли я как-то неправильно считываю, то-ли сохраняю в файл что-то не то. Помогите умоляю!:с

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

int isValidPositiveNaturalNumber2(const char* str) { // Check
int r = 0;
while (str[r] != '\0') {
if (!isdigit(str[r]) || isalpha(str[r])) {
return 0;
}
r++;
}
return 1;
}

typedef enum { // Enum
MALE,
FEMALE
} Gender;

typedef struct { // Struct
int year;
int month;
int day;
} Date;

typedef struct Student { // Struct
char *lastName;
char *firstName;
char *middleName;
Date birthDate;
char *group;
Gender gender;
struct Student* next;
} Student;

void freeStudentList(Student *students) { // Free list of students
Student *current = students;
while (current != NULL) {
Student *temp = current;
current = current->next;
free(temp->lastName);
free(temp->firstName);
free(temp->middleName);
free(temp->group);
free(temp);
}
}

void appendStudent(Student **head, Student *newStudent) { // Append student to the end of the list
if (*head == NULL) {
*head = newStudent;
} else {
Student *current = *head;
while (current->next != NULL) {
current = current->next;
}
current->next = newStudent;
}
}

Student* createStudentNode(const char *lastName, const char *firstName, const char *middleName, Date birthDate, const char *group, Gender gender) { // Create a new student node
Student *newStudent = (Student*)malloc(sizeof(Student));
if (newStudent == NULL) {
printf("Error: Failed to allocate memory for a new student\n");
return NULL;
}

newStudent->lastName = strdup(lastName);
newStudent->firstName = strdup(firstName);
newStudent->middleName = strdup(middleName);
newStudent->birthDate = birthDate;
newStudent->group = strdup(group);
newStudent->gender = gender;
newStudent->next = NULL;

return newStudent;
}

void printStudentList(Student *students) { // Print the list of students
FILE *file = fopen("data.bin", "rb"); // Open file for reading in binary mode
if (file == NULL) {
printf("The list of students is empty.\n");
return;
}

// Read data from the file
Student *current = (Student*)malloc(sizeof(Student));
if (current == NULL) {
printf("Error: Failed to allocate memory for a student.\n");
fclose(file);
return;
}

size_t read = fread(current, sizeof(Student), 1, file);
if (read != 1) {
printf("The list of students is empty.\n");
fclose(file);
free(current);
return;
}

printf("List of students:\n");
while (!feof(file)) {
printf("%s %s %s\n", current->lastName, current->firstName, current->group);
read = fread(current, sizeof(Student), 1, file);
}

fclose(file);
free(current);
}

void appendNewStudent(Student **head) { // Append a new student
char lastName[50];
char firstName[50];
char middleName[50];
char yearStr[20], monthStr[20], dayStr[20], genderChoiceStr[20];
int year, month, day, genderChoice;
char group[10];

printf("Enter the student's last name: ");
scanf("%s", lastName);
printf("Enter the student's first name: ");
scanf("%s", firstName);
printf("Enter the student's middle name: ");
scanf("%s", middleName);

while (1) {
printf("Enter the student's birth year: ");
year = scanf("%s", yearStr);

if (year != 1 || !isValidPositiveNaturalNumber2(yearStr)) {
printf("Invalid input. Please enter a positive integer.\n");
while (getchar() != '\n');
continue;
}

year = atoi(yearStr);

if (year < 1900 || year > 2024) {
printf("The birth year should be between 1900 and 2024. Please try again.\n");
} else {
break;
}
}

// Similar loops for month and day inputs

printf("Enter the student's group: ");
scanf("%s", group);

// Similar loop for gender input

Gender gender = genderChoice == 0 ? MALE : FEMALE;

Date birthDate = {year, month, day};

Student *newStudent = createStudentNode(lastName, firstName, middleName, birthDate, group, gender);
if (newStudent == NULL) {
printf("Error: Failed to add a new student.\n");
return;
}

appendStudent(head, newStudent);

// Get data from the file
FILE *file = fopen("data.bin", "ab"); // Open file for appending in binary mode
if (file == NULL) {
printf("Error: Failed to open the file for writing.\n");
return;
}

// Write data of the new student to the file
size_t written = fwrite(newStudent, sizeof(Student), 1, file);
if (written != 1) {
printf("Error writing to the file.\n");
} else {
printf("The student has been successfully added to the list and written to the file.\n");
}

fclose(file);
}

void menu(Student *students) { // Main menu
char userChoiceStr[20];
int result;

while (1) {
result = scanf("%s", userChoiceStr);

if (result != 1 || !isValidPositiveNaturalNumber2(userChoiceStr)) {
printf("Invalid input. Please enter a positive integer.\n");
while (getchar() != '\n');
continue;
}

result = atoi(userChoiceStr);

if (result == 4) {
break;
}

switch (result) {
case 1:
printStudentList(students);
break;

case 2:
appendNewStudent(&students);
break;

case 3:
printf("sdfsd");
break;

default:
printf("Invalid choice, please select again.\n");
break;
}
}
}

int main() {
Student* students = NULL; // Initialization

menu(students);

freeStudentList(students); // Cleanup

return 0;
}

C

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <ctype.h>



int isValidPositiveNaturalNumber2(const char* str) { // Check

    int r = 0;

    while (str[r] != '\0') {

        if (!isdigit(str[r]) || isalpha(str[r])) {

            return 0;

        }

        r++;

    }

    return 1;

}



typedef enum { // Enum

    MALE,

    FEMALE

} Gender;



typedef struct { // Struct

    int year;

    int month;

    int day;

} Date;



typedef struct Student { // Struct

    char *lastName;

    char *firstName;

    char *middleName;

    Date birthDate;

    char *group;

    Gender gender;

    struct Student* next;

} Student;



void freeStudentList(Student *students) { // Free list of students

    Student *current = students;

    while (current != NULL) {

        Student *temp = current;

        current = current->next;

        free(temp->lastName);

        free(temp->firstName);

        free(temp->middleName);

        free(temp->group);

        free(temp);

    }

}



void appendStudent(Student **head, Student *newStudent) { // Append student to the end of the list

    if (*head == NULL) {

        *head = newStudent;

    } else {

        Student *current = *head;

        while (current->next != NULL) {

            current = current->next;

        }

        current->next = newStudent;

    }

}



Student* createStudentNode(const char *lastName, const char *firstName, const char *middleName, Date birthDate, const char *group, Gender gender) { // Create a new student node

    Student *newStudent = (Student*)malloc(sizeof(Student));

    if (newStudent == NULL) {

        printf("Error: Failed to allocate memory for a new student\n");

        return NULL;

    }



    newStudent->lastName = strdup(lastName);

    newStudent->firstName = strdup(firstName);

    newStudent->middleName = strdup(middleName);

    newStudent->birthDate = birthDate;

    newStudent->group = strdup(group);

    newStudent->gender = gender;

    newStudent->next = NULL;



    return newStudent;

}



void printStudentList(Student *students) { // Print the list of students

    FILE *file = fopen("data.bin", "rb"); // Open file for reading in binary mode

    if (file == NULL) {

        printf("The list of students is empty.\n");

        return;

    }



    // Read data from the file

    Student *current = (Student*)malloc(sizeof(Student));

    if (current == NULL) {

        printf("Error: Failed to allocate memory for a student.\n");

        fclose(file);

        return;

    }



    size_t read = fread(current, sizeof(Student), 1, file);

    if (read != 1) {

        printf("The list of students is empty.\n");

        fclose(file);

        free(current);

        return;

    }



    printf("List of students:\n");

    while (!feof(file)) {

        printf("%s %s %s\n", current->lastName, current->firstName, current->group);

        read = fread(current, sizeof(Student), 1, file);

    }



    fclose(file);

    free(current);

}



void appendNewStudent(Student **head) { // Append a new student

    char lastName[50];

    char firstName[50];

    char middleName[50];

    char yearStr[20], monthStr[20], dayStr[20], genderChoiceStr[20];

    int year, month, day, genderChoice;

    char group[10];



    printf("Enter the student's last name: ");

    scanf("%s", lastName);

    printf("Enter the student's first name: ");

    scanf("%s", firstName);

    printf("Enter the student's middle name: ");

    scanf("%s", middleName);



    while (1) {

        printf("Enter the student's birth year: ");

        year = scanf("%s", yearStr);



        if (year != 1 || !isValidPositiveNaturalNumber2(yearStr)) {

            printf("Invalid input. Please enter a positive integer.\n");

            while (getchar() != '\n');

            continue;

        }



        year = atoi(yearStr);



        if (year < 1900 || year > 2024) {

            printf("The birth year should be between 1900 and 2024. Please try again.\n");

        } else {

            break;

        }

    }



    // Similar loops for month and day inputs



    printf("Enter the student's group: ");

    scanf("%s", group);



    // Similar loop for gender input



    Gender gender = genderChoice == 0 ? MALE : FEMALE;



    Date birthDate = {year, month, day};



    Student *newStudent = createStudentNode(lastName, firstName, middleName, birthDate, group, gender);

    if (newStudent == NULL) {

        printf("Error: Failed to add a new student.\n");

        return;

    }



    appendStudent(head, newStudent);



    // Get data from the file

    FILE *file = fopen("data.bin", "ab"); // Open file for appending in binary mode

    if (file == NULL) {

        printf("Error: Failed to open the file for writing.\n");

        return;

    }



    // Write data of the new student to the file

    size_t written = fwrite(newStudent, sizeof(Student), 1, file);

    if (written != 1) {

        printf("Error writing to the file.\n");

    } else {

        printf("The student has been successfully added to the list and written to the file.\n");

    }



    fclose(file);

}



void menu(Student *students) { // Main menu

    char userChoiceStr[20];

    int result;



    while (1) {

        result = scanf("%s", userChoiceStr);



        if (result != 1 || !isValidPositiveNaturalNumber2(userChoiceStr)) {

            printf("Invalid input. Please enter a positive integer.\n");

            while (getchar() != '\n');

            continue;

        }



        result = atoi(userChoiceStr);



        if (result == 4) {

            break;

        }



        switch (result) {

            case 1:

                printStudentList(students);

                break;



            case 2:

                appendNewStudent(&students);

                break;

        

            case 3:

                printf("sdfsd");

                break;



            default:

                printf("Invalid choice, please select again.\n");

                break;

        }

    }

}



int main() {

    Student* students = NULL; // Initialization



    menu(students);



    freeStudentList(students); // Cleanup



    return 0;

}