in_avail() not working for me.

[johnwestman]

I am using windows. I copied this program from Reference section in this site, as it is.When I run the program it always shows 0 additional characters, no matter what.

#include <iostream>
using namespace std;

int main () {

  streamsize size;
  char ch;

  streambuf * pbuf;
  pbuf = cin.rdbuf();

  cout << "Please enter some characters: ";
  cin >> ch;

  size = pbuf->in_avail();

  cout << "The first character you entered is: " << ch << endl;
  cout << size << " additional characters in input buffer" << endl;

  return 0;
}

[Cubbi]

The effect of in_avail() is entirely implementation-defined. In particular, In many C++ implementations (likely including yours), std::cin has no buffer by default, so in_avail() always returns zero.

If you're using gcc, add the line

cin.sync_with_stdio(false);

somewhere near the beginning of main. That turns on cin's buffer in GNU library (but, for example, in LLVM library, you'd still have zero buffer)

[johnwestman]

Thanks so much Cubbi. I added the line cin.sync_with_stdio(false); and it worked. The only problem is that it returns one more than the actual no. of additional characters.

Although I can manage it by manually subtracting 1 from returned value, I was curious why would the function do so.