std::basic_istream::gcount

From cppreference.com
< cpplrm; | iolrm; | basic istream
std::streamsize gcount() const;

Returns the number of characters extracted by the last unformatted input operation.

The following member functions of basic_istream change the value of subsequent gcount() calls:

The following functions set gcount() to zero:

Parameters

(none)

Return value

The number of characters extracted by the last unformatted input operation

Example

#include <iostream>
#include <sstream>

int main()
{
    char x[20];
    std::istringstream stream("Hello World");

    stream.read(x, sizeof x);
    std::cout << "Characters extracted: " << stream.gcount();
}

Output:

Characters extracted: 11