How do I flush the cin buffer?

Question

How do I clear the cin buffer in C++?

Answer 1

The following should work:

cin.flush();

On some systems it's not available and then you can use:

cin.ignore(INT_MAX);

Answer 2

possibly:

std::cin.ignore(INT_MAX);

this would read in and ignore everything until EOF. (you can also supply a second argument which is the character to read until (ex: '\n' to ignore a single line).

Also: You probably want to do a: std::cin.clear(); after this too to reset the stream state.

Answer 3

I would prefer the C++ size constraints over the C versions:

// Ignore to the end of file
cin.ignore(std::numeric_limits<std::streamsize>::max())

// Ignore to the end of line
cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n')

Answer 4

I prefer:

cin.clear();
fflush(stdin);

There's an example where cin.ignore just doesn't cut it, but I can't think of it at the moment.

Answer 5

How about:

cin.ignore(cin.rdbuf()->in_avail());

Answer 6

int i;
  cout << "Please enter an integer value: ";

  // cin >> i; leaves '\n' among possible other junk in the buffer. 
  // '\n' also happens to be the default delim character for getline() below.
  cin >> i; 
  if (cin.fail()) 
  {
    cout << "\ncin failed - substituting: i=1;\n\n";
    i = 1;
  }
  cin.clear(); cin.ignore(INT_MAX,'\n'); 

  cout << "The value you entered is: " << i << " and its double is " << i*2 << ".\n\n";

  string myString;
  cout << "What's your full name? (spaces inclded) \n";
  getline (cin, myString);
  cout << "\nHello '" << myString << "'.\n\n\n";