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.

[edit]Parameters

[edit]Return value

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

[edit]Exceptions

May throw implementation-defined exceptions.

[edit]Notes

By default, the standard streamstd::cout is tied tostd::cin andstd::cerr. Similarly, its wide counterpartstd::wcout is tied tostd::wcin andstd::wcerr.

[edit]Example

#include <fstream>#include <iomanip>#include <iostream>#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(): "<<std::quoted(value)<<"\n";    is.clear();    is.tie(&os);     is>> value; std::cout<<"Result after tie(): "<<std::quoted(value)<<"\n";}

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

[edit]Defect reports

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

1. ↑std::basic_ostream::flush() is anUnformattedOutputFunction, so it creates a sentry object while being called. Whenflush() is called on a stream object, theconstructor of the sentry object will callflush() on its tied stream, and thatflush() will construct another sentry object and its constructor will callflush() on the tied stream of that stream and so on. Therefore, if streamsa andb are (directly or indirectly) tied to each other, callinga.flush() will eventually callb.flush(), which will eventually calla.flush(), and will result in an infinite loop.

• In other languages

• Deutsch
• Español
• Français
• Italiano
• 日本語
• Português
• Русский
• 中文