Fstream

#include <iostream>
#include <fstream>
#include <string>

using namespace std;

void classmates();
void add();
void update();
void delet();

int main() {
    int option;

    classmates();

    cout << "---------------------------------------- \n";
    cout << "   CLASSMATE NAMES \n\n choose options: ";
    cout << "\n [1] add";
    cout << "\n [2] update";
    cout << "\n [3] delete";
    cout << "\n Enter your option: ";
    cin >> option;

    switch (option) {
    case 1:
        cout << "---------------------------------------- \n";
        cout << " ADD NAMES \n\n";

        add();
        classmates();
        break;
    case 2:
        cout << "---------------------------------------- \n";
        cout << " UPDATE NAMES \n\n";

        update();
        classmates();
        break;
    case 3:
        cout << "---------------------------------------- \n";
        cout << " DELETE NAMES \n\n";

        delet();
        classmates();
        break;
    default:
        cout << "Input is Invalid. Mismatch. \n";
    }
    return 0;
}
void add(){
    string line;
    fstream tex;

    cout << "Enter New Classmates: ";
    cin >> line;

    tex.open("tex.txt", ios::app);
    tex << "\n" << line;
    tex.close();
}

void classmates() {
    string line;
    fstream classmates;

    classmates.open("tex.txt");
    while (getline(classmates, line)) {
        cout << line << "\n";
    }
    classmates.close();
}

void update() {
    string line, up, rep;
    fstream classmates;

    cout << "Find: ";
    cin >> up;
    cout << "Replace: ";
    cin >> rep;

    classmates.open("tex.txt", ios::in);
    while (getline(classmates, line)) {
        if (line.find(up)) {
            cout << "\n" << rep;
        }
    }
    classmates.close();
}

void delet() {
    string line, up, rep;
    fstream classmates;

    classmates.open("tex.txt", ios::out);
    while (getline(classmates, line)) {
            cout << "\n";
    }
    classmates.close();
}