How do I take input from user as a password and compare it with the data in the file in c++

Question

I am making a project in C++, in which I need to make a login system. I wrote the code below, but I am not able to figure out why the password doesn't match when we run case 2 in the login() function.

Core concept:
First, we need to register the user name and password, which is done in case 1 of the login() function. Then, the user gets access to the information through his username and password.

Problem faced:
When I try to use a username and password of an already-registered user, the password doesn't match. I checked the stored password and entered password by printing them to the console, and they are the same. But, when we compare both by using the == operator, it gives a false result. Can anyone explain why?

#include<iostream>
#include<fstream>
#include<cstdlib>
#include<conio.h>

using namespace std;

int login(void);

int main(void)
{
    cout<<"Login system\n";

    int d;
    d = login();

    if(d)
        cout<<"Access granted!!"<<endl;
    else
        cout<<"Access denied!!"<<endl;
}

int login(void)
{
    system("CLS");
    cout<<"\n\n\n";

    string username, password;

    fstream file;

    int choice;
    again:

    cout<<"1.Add new user\n2.login\n";
    cin>>choice;

    switch(choice)
    {
        case 1:
        {
            file.open("Login details.txt", ios :: app);
            cout<<"Enter new username and password\n";

            cin>>username;
            cin>>password;
            file<<username<<"\t\t";
            file<<password<<endl;
            return 1;
            break;
        }

        case 2:
        {
            file.open("Login details.txt", ios :: in);

            string tempname, temp_pass, k;
            char temp_pas[100];
            int p = 0;
            cout<<"Enter your username and password\n";
            cin>>tempname;
            do
            {
                temp_pas[p] = getch();
                if(temp_pas[p] != '\r')
                cout<<"*";
                p++;
            }while(temp_pas[p - 1] != '\r');
            
            cout<<endl;
            
            for(int i = 0; i < p; i++)
            {
                temp_pass += temp_pas[i];
            }

            while(file)
            {
                file>>username;
                file>>password;

                cout<<q<<endl<<w<<endl;
                if(tempname == username && temp_pass == password)
                {
                    cout<<"access granted\n";
                    return 1;
                }
            }
            cout<<"Invalid username or password\n";
            return 0;

            break;
        }
       default
             {
              cout<<"Choose a valid option"<<endl;
              goto again;
              }
    }
}

Answer 1

you're making it all hard, just simply save id and password as string into file and later on read the file and later on to check use string.compare() function

Answer 2

Change the for loop from: for (int i = 0; i < p; i++) to: for (int i = 0; i < p-1; i++)

The compiler is currently reading \r as being the last character of the entered password.