kbhit() with streambuf::is_avail()

Sun May 6 06:56:00 GMT 2001

How do I find out if new input from cin input stream (or possibly stdin) is
available?
I was expecting I could use the is_avail() member function of istream for
this.
But the sample code from:
http://www.cplusplus.com/ref/iostream/streambuf/in_avail.html
seems to indicate that is_avail() always returns 0 !!?
// http://www.cplusplus.com/ref/iostream/streambuf/in_avail.html
// in_avail () example
#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;
 cout << cin.rdbuf()->in_avail() << " additional characters in input
buffer" << endl;
 cin >> ch;
 size = pbuf->in_avail();
 cout << "The second character you entered is: " << ch << endl;
 cout << size << " additional characters in input buffer" << endl;
 cout << cin.rdbuf()->in_avail() << " additional characters in input
buffer" << endl;
 return 0;
}
After compiling under cygwin (dll 1.3.1-1) and running I get:
$ gcc test.cpp /lib/libstdc++.a
$ ./a.exe
Please enter some characters: cygwin
The first character you entered is: c
0 additional characters in input buffer
The second character you entered is: y
0 additional characters in input buffer
I was expecting the in_avail() function to return 6 after the first cin>>ch;
instead I get 0 !?
Are my expectations wrong?
Is there another non-blocking way to find out if more keystrokes are
available or not?
Berni.
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