Namespaces
Variants

std::basic_ios<CharT,Traits>:: rdbuf

From cppreference.net
C++
Input/output library
std::basic_ios
std:: basic_streambuf < CharT, Traits > * rdbuf ( ) const ;
(1)
std:: basic_streambuf < CharT, Traits > * rdbuf ( std:: basic_streambuf < CharT, Traits > * sb ) ;
(2)

Manages the associated stream buffer.

1) Returns the associated stream buffer. If there is no associated stream buffer, returns a null pointer.
2) Sets the associated stream buffer to sb . The error state is cleared by calling clear() . Returns the associated stream buffer before the operation. If there is no associated stream buffer, returns a null pointer.

Contents

Parameters

sb - Stream buffer to associate to.

Return value

The associated stream buffer, or a null pointer if there was no associated stream buffer.

Exceptions

May throw implementation-defined exceptions.

Example

Run this code 
#include <iostream>
#include <sstream>
int main()
{
    std::ostringstream local;
    auto cout_buff = std::cout.rdbuf(); // save pointer to std::cout buffer
    std::cout.rdbuf(local.rdbuf()); // substitute internal std::cout buffer with
                                    // buffer of 'local' object
    // now std::cout work with 'local' buffer
    // you don't see this message
    std::cout << "some message";
    // go back to old buffer
    std::cout.rdbuf(cout_buff);
    // you will see this message
    std::cout << "back to default buffer\n";
    // print 'local' content
    std::cout << "local content: " << local.str() << "\n";
}

Output: 

back to default buffer
local content: some message

See also

replaces the rdbuf without clearing its error state
(protected member function)