Difference between std::cin and scanf() applied to string

Question

I am trying to get the first character of a string written to a variable of type char. With std::cin (commented out) it works fine, but with scanf() I get runtime error. It crus

Answer 1

scanf knows nothing about std::string. If you want to read into the underlying character array you must write scanf("%s", s.data());. But do make sure that the string's underlying buffer is large enough by using std::string::resize(number)!

Generally: don't use scanf with std::string.

Another alternative if you want to use scanf and std::string

int main()
{
    char myText[64];
    scanf("%s", myText);

    std::string newString(myText);
    std::cout << newString << '\n';

    return 0;
}

Construct the string after reading.

Now for the way directly on the string:

int main()
{
    std::string newString;
    newString.resize(100); // Or whatever size   
    scanf("%s", newString.data());

    std::cout << newString << '\n';

    return 0;
}

Although this will of course only read until the next space. So if you want to read a whole line, you would be better off with:

std::string s;
std::getline(std::cin, s);