Cin.getline() function in if statement

Question

while (true)
{
    cout << "Please enter a  some text: ";
    cin.getline( sendbuf, 100, '\n' );
    i = i + 1;
    if (? = "q") // here i am looking for something that if i press q i should come out of look
    {
        break;
    }
}

I am a beginner and eager to learn more. I want to ask if I can provide some way to terminate this loop by typing char 'q' after typing my all desire strings data.

EDIT my sendbuf is char* sendbuf, so I don't think so using std::string will help me.

Answer 1

Don't use a char array, use std::string class and you get comparison with == for free:

#include <string>

std::string line;
while (true) {
    cout << "Enter string: ";
    std::getline(cin, line);
    if (line == "q" || line == "Q") break;
}

This way the size of the line is not limited to whatever the size of sendbuf is.

If you later need to send data to a function that expects a char* , you take the address of the first element ( &line[0] ) or simply call line.data() . There's also size member function that returns, you guessed it, the size of the string. You're in no way limited by archaic interfaces that work on C-style char arrays. A string is a char array, after all.

Recommened reading: string class documentation.

Answer 2

if ( !cin || std::strcmp( sendbuf, "q" ) == 0 ) break;

Answer 3

The obvious solution is to use a std::string , and put all of your tests in the while condition:

std::string line;
while ( std::getline( std::cin, line ) && line != "q" ) {
    //  ...
}

In practice, you'll probably want a more complicated test on line , probably factored out into a separate function. Similarly, if you always want a prompt:

std::istream&
getLineWithPrompt( std::istream& source, std::string const& prompt, std::string& line )
{
    std::cout << prompt;
    return std::getline( source, line );
}