Doesnt read data from file

Question

What have I've done wrong? I'm entering correct credentials and program keep saying "Invalid username or password!"

void user::login()
{
    string username, uname;
    string password, pword;

    cout << "Enter your username: \n"; 
    cin >> uname;
    cout << "Enter your password: \n"; 
    cin >> pword;

    ifstream data("data.txt");
    if (data.is_open())
    {
        while (!data.eof())
        {
            data >> username >> password;

            if (uname == username && pword == password)
            {
                cout << "Login successfully!\n";
                Sleep(2000);
                mainMenu();
            }
            else if (uname != username || pword != password)
            {
                cout << "Invalid username or password!\n";
                Sleep(2000);
                login();
            }
        }
        data.close();
    }
}

Why dont you try printing username and password and see whats wrong? Besides that calling 'eof' in a loop is wrong, http://stackoverflow.com/questions/5605125/why-is-iostreameof-inside-a-loop-condition-considered-wrong — Arunmu, Dec 08 '15 at 12:36
You recurse into the function, which then *opens the file again from the beginning*. You should not be calling `login` inside of `login`, but continuing on with the `while` loop (checking for `eof` is not good though...) to keep reading the file for a match. — crashmstr, Dec 08 '15 at 12:36

kay · Accepted Answer · 2015-12-08T13:29:51.240

Please see my inline comments:

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

// You should not use using namespace std! In here only for brevity.
using namespace std;

// Use a proper API: return account name on success, empty string otherwise.
// Throw an exception on error.
string login() throw (const char*)
{
    // embrace C++11!
    if (ifstream data {"data.txt"}) {
        string username, uname;
        string password, pword;

        // Always test if the IO is broken!
        if (!((cout << "Enter your username: \n") &&
              (cin >> uname) &&
              (cout << "Enter your password: \n") &&
              (cin >> pword))) {
            throw "Could not get user credentials.";
        }

        // debug output, remove in production:
        cerr << "Credentials: " << uname << " (" << pword << ")" << endl;

        // read a line from data.txt
        while (data >> username >> password) {
            // debug output, remove in production:
            cerr << "Read: " << username << " (" << password << ")" << endl;

            // compare input:
            if ((uname == username) && (pword == password)) {
                return username;
            }
        }

        // no input matched
        return "";

        // no need to explicitly close the stream
    } else {
        throw "Password file could not be opened.";
    }
}

int main() {
    string account_name;
    try {
        // The caller should include a loop, not the login function.
        account_name = login();
    } catch (const char *message) {
        cerr << "Error: " << message << endl;
        return 1;
    }
    if (!account_name.empty()) {
        cout << "Hello, " << account_name << endl;
    } else {
        cout << "Could not authenticate!" << endl;
    }
    return 0;
}

data.txt:

Neuroosi hunter2
Kay supersecret
Arunmu hello
crashmstr password1234

@Neuroosi, you're welcome. Please consider do click the check mark on the left of my answer to mark the question to as solved. — kay, Dec 09 '15 at 15:09

Doesnt read data from file

1 Answers1