std::basic_ostream<CharT,Traits>::basic_ostream

 

C++

Compiler support

Freestanding and hosted

Language

Standard library

Standard library headers

Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

Metaprogramming library (C++11)

Diagnostics library

General utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Localizations library

Input/output library

Filesystem library (C++17)

Regular expressions library (C++11)

Concurrency support library (C++11)

Execution support library (C++26)

Technical specifications

Symbols index

External libraries

 

Input/output library

I/O manipulators

Print functions (C++23)

C-style I/O

Buffers

basic_streambuf

basic_filebuf

basic_stringbuf

basic_spanbuf (C++23)

strstreambuf (C++98/26*)

basic_syncbuf (C++20)

Streams

Abstractions

ios_base

basic_ios

basic_istream

basic_ostream

basic_iostream

File I/O

basic_ifstream

basic_ofstream

basic_fstream

String I/O

basic_istringstream

basic_ostringstream

basic_stringstream

Array I/O

basic_ispanstream (C++23)

basic_ospanstream (C++23)

basic_spanstream (C++23)

istrstream (C++98/26*)

ostrstream (C++98/26*)

strstream (C++98/26*)

Synchronized Output

basic_osyncstream (C++20)

Types

streamoff

streamsize

fpos

Error category interface

iostream_category (C++11)

io_errc (C++11)

 

std::basic_ostream

Global objects
coutwcout	cerrwcerr	clogwclog
Member functions
basic_ostream::basic_ostream
basic_ostream::~basic_ostream
basic_ostream::operator= (C++11)
Formatted output
basic_ostream::operator<<
Unformatted output
basic_ostream::put
basic_ostream::write
Positioning
basic_ostream::tellp
basic_ostream::seekp
Miscellaneous
basic_ostream::flush
basic_ostream::swap (C++11)
Member classes
basic_ostream::sentry
Non-member functions
operator<<(std::basic_ostream)
print(std::ostream) (C++23)
println(std::ostream) (C++23)
vprint_unicode(std::ostream) (C++23)
vprint_nonunicode(std::ostream) (C++23)

 

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

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 <iostream>
#include <sstream>
#include <utility>
 
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::ostringstream() << 7.1);
    myout << s2.str() << '\n';
 
    std::ostream dev_null{nullptr}; // see Notes above
    dev_null << "no-op";
}

Output:

7.1