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std::basic_ios::rdbuf(3)       C++ Standard Libary	std::basic_ios::rdbuf(3)

NAME
     std::basic_ios::rdbuf - std::basic_ios::rdbuf

Synopsis
	std::basic_streambuf<CharT,	   Traits>*	   rdbuf()	  const;
     (1)
	std::basic_streambuf<CharT, Traits>* rdbuf(  std::basic_streambuf<CharT,
     (2)
	Traits>* sb );

	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.

Parameters
	sb - stream buffer to associate to

Return value
	The associated stream buffer, or a null pointer if there was no  associ-
     ated 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
	set_rdbuf replaces the rdbuf without clearing its error state
		  (protected member function)

http://cppreference.com 	   2024.06.10		std::basic_ios::rdbuf(3)
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