Using Getline(Cin, S) After Cin [Duplicate]

Question

I need the following program to take the entire line of user input and put it into string names:

cout << "Enter the number: ";
int number;
cin >> number;

cout << "Enter names: ";
string names;

getline(cin, names);

With the cin >> number command before the getline() command however (which I'm guessing is the issue), it won't allow me to input names. Why?

I heard something about a cin.clear() command, but I have no idea how this works or why this is even necessary.

Accepted Answer

cout << "Enter the number: ";
int number;
cin >> number;

cin.ignore(256, '\n'); // remaining input characters up to the next newline character
                       // are ignored

cout << "Enter names: ";
string names;
getline(cin, names);

Answer 2

Another way of doing it is to put a

cin.ignore ( std::numeric_limits<std::streamsize>::max(), '\n' );

after your cin>>number; to flush the input buffer completely (rejecting all of the extra characters until a newline is found). You need to #include <limits> to get the max() method.

Accepted Answer

cout << "Enter the number: ";
int number;
if (cin >> number)
{
    // throw away the rest of the line 
    char c;
    while (cin.get(c) && c != '\n')
        if (!std::isspace(c))
        {
            std::cerr << "ERROR unexpected character '" << c << "' found\n";
            exit(EXIT_FAILURE);
        }
    cout << "Enter names: ";
    string name;
    // keep getting lines until EOF (or "bad" e.g. error reading redirected file)...
    while (getline(cin, name))
        ...use name...
}
else
{
    std::cerr << "ERROR reading number\n";
    exit(EXIT_FAILURE);
}

In the code above, this bit...

    char c;
    while (cin.get(c) && c != '\n')
        if (!std::isspace(c))
        {
            std::cerr << "ERROR unexpected character '" << c << "' found\n";
            exit(EXIT_FAILURE);
        }

...checks the rest of the input line after the number contains only whitespace.

Must Read

Why not just use ignore?

That's pretty verbose, so using ignore on the stream after >> x is an oft-recommended alternative way to discard content through to the next newline, but it risks throwing away non-whitespace content and in doing so, overlooking corrupt data in the file. You may or may not care, depending on whether the file's content's trusted, how important it is to avoid processing corrupt data etc..

Using Getline(Cin, S) After Cin [Duplicate]

13 Answers

Must Read

Why not just use ignore?

David Miller