New line character not appearing

Question

Recently I wrote some code in which I need to identify a newline character. I believed using if(str == "") would not return true if the character was a \\n but I was wrong. If you run the following code with

steven 

bar

inside output.txt you will get no text at 2 which makes no sense because there should be a newline character there. Im pretty new to programming so here is the code.(It works if i if(str == '\\n') but im curious why the newline character isnt detected by if(str == "") .) Please clarify why C++ doesnt recognize the newline here is the code.

#include <iostream>
#include <fstream>
#include <string>
#include <windows.h>

using namespace std;

int main()
{
    ifstream output;
    string line;
    int i = 1;
    output.open("output.txt");
    while(i <= 3)
    {
        getline(output, line, '\n');
        if(line == "")
        {
            cout << "no text found at "<< i << endl;
        }
        else
        {
            cout << "text at " << i << endl;
        }
        i++;
    }
    system("PAUSE");
}

Answer 1

According to cppreference :

getline [...] Extracts characters from input and appends them to str until one of the following occurs [...]

b) the next available input character is delim , [...] in which case the delimiter character is extracted from input , but is not appended to str .

So the string returned for your 2nd line is empty because the \\n delimiter is not appended to it.

---

You can confirm this behaviour by using a visible char as delimiter and checking the output :

output.open("output.txt");
getline(output, line, 'n');
cout << line << endl; // outputs "steve"

instead of steven , you get steve because the delimiter n is not appended.

Answer 2

The double quotation marks "" is empty string. New line character is different from empty string. Let's think in reverse, if you write

std::cout << "";

and

std::cout << std::endl;

First one will print nothing and cursor will stay at same line, while the second one will move the cursor to next line.