NAME

std::basic_ios::tie - std::basic_ios::tie

Synopsis

std::basic_ostream<CharT,Traits>* tie() const; (1)
std::basic_ostream<CharT,Traits>* tie( std::basic_ostream<CharT,Traits>* str ); (2)

Manages the tied stream. A tied stream is an output stream which is synchronized
with the sequence controlled by the stream buffer (rdbuf()), that is, flush() is
called on the tied stream before any input/output operation on *this.

1) Returns the current tied stream. If there is no tied stream, a null pointer is
returned.
2) Sets the current tied stream to str. Returns the tied stream before the
operation. If there is no tied stream, a null pointer is returned.

Parameters

str - an output stream to set as the tied stream

Return value

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

Exceptions

May throw implementation-defined exceptions.

Notes

By default, the standard stream cout is tied to cin and cerr. Similarly, its wide
counterpart wcout is tied to wcin and wcerr.

Example

// Run this code

#include <iostream>
#include <fstream>
#include <string>

int main()
{
std::ofstream os("test.txt");
std::ifstream is("test.txt");
std::string value("0");

os << "Hello";
is >> value;

std::cout << "Result before tie(): \"" << value << "\"\n";
is.clear();
is.tie(&os);

is >> value;

std::cout << "Result after tie(): \"" << value << "\"\n";
}

Output:

Result before tie(): "0"
Result after tie(): "Hello"