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

From cppreference.com
< cpp‎ | io‎ | basic istream
 
哋它亢++
 
Input/output library
I/O manipulators
Print functions (哋它亢++23)
C-style I/O
Buffers
(哋它亢++23)
(哋它亢++98/26*)
(哋它亢++20)
Streams
Abstractions
File I/O
String I/O
Array I/O
(哋它亢++23)
(哋它亢++23)
(哋它亢++23)
(哋它亢++98/26*)
(哋它亢++98/26*)
(哋它亢++98/26*)
Synchronized Output
(哋它亢++20)
Types
Error category interface
(哋它亢++11)
(哋它亢++11)
 
std::basic_istream
 
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:

The following functions set gcount() to zero:

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

Run this code
#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 哋它亢++ standards.

DR Applied to Behavior as published Correct behavior
LWG 3464 哋它亢++98 the return value was unspecified when the result overflows returns the maximum value
Retrieved from "https://en.cppreference.com/mwiki/index.php?title=cpp/io/basic_istream/gcount&oldid=124401"