NAME¶

std::basic_ostream::basic_ostream - std::basic_ostream::basic_ostream

Synopsis¶

explicit basic_ostream( std::basic_streambuf<CharT, Traits>* sb ); (1)
protected: (2) (since C++11)
basic_ostream( const basic_ostream& rhs ) = delete;
protected: (3) (since C++11)
basic_ostream( basic_ostream&& rhs );

1) Constructs the basic_ostream object, assigning initial values to the base class
by calling basic_ios::init(sb).

2) The copy constructor is protected, and is deleted. Output streams are not
copyable.

3) The move constructor uses basic_ios<CharT, Traits>::move(rhs) to move all
basic_ios members, except for the rdbuf(), from rhs into *this. This move
constructor is protected: it is called by the move constructors of movable output
stream classes std::basic_ofstream and std::basic_ostringstream, which know how to
correctly move the associated streambuffer.

Parameters¶

sb - streambuffer to use as output sequence
rhs - basic_ostream to initialize from

Notes¶

Because basic_ios::init(sb) sets badbit when sb is a null pointer, and because
basic_ostream::sentry does nothing if the stream is already in a failed state,
writing to a stream constructed from a null pointer sb is a no-op.

Example¶

// Run this code

#include <sstream>
#include <utility>
#include <iostream>

int main()
{
// ERROR: copy ctor is deleted
// std::ostream myout(std::cout);

// OK: shares buffer with cout
std::ostream myout(std::cout.rdbuf());

// ERROR: move constructor is protected
// std::ostream s2(std::move(std::ostringstream() << 7.1));

// OK: move ctor called through the derived class
std::ostringstream s2(std::move(std::ostringstream() << 7.1));
myout << s2.str() << '\n';

std::ostream dev_null{nullptr}; // see Notes above
dev_null << "no-op";
}

Output:¶

7.1