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std::basic_istream<CharT,Traits>::gcount

std::streamsize gcount() const;

Returns the number of characters extracted by the last unformatted input operation, or the maximum representable value of std::streamsize if the number is not representable.

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

  • move constructor
  • swap()
  • get()
  • getline()
  • ignore()
  • read()
  • readsome()
  • operator>>(basic_streambuf*)

The following functions set gcount() to zero:

  • constructor
  • putback()
  • unget()
  • peek()

Parameters

(none)

Return value

The number of characters extracted by the last unformatted input operation, or the maximum representable value of std::streamsize if the number is not representable.

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

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR Applied to Behavior as published Correct behavior
LWG 3464 C++98 the return value was unspecified when the result overflows returns the maximum value

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https://en.cppreference.com/cpp/io/basic_istream/gcount

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