std::basic_ostringstream<CharT,Traits,Allocator>::basic_ostringstream

 

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_ostringstream

Member functions

basic_ostringstream::basic_ostringstream

basic_ostringstream::operator=

basic_ostringstream::swap (C++11)

basic_ostringstream::rdbuf

String operations

basic_ostringstream::str

basic_ostringstream::view (C++20)

Non-member functions

swap(std::basic_ostringstream) (C++11)

 

	(1)
explicit basic_ostringstream( std::ios_base::openmode mode =                                   std::ios_base::out );			(until C++11)
explicit basic_ostringstream( std::ios_base::openmode mode );			(since C++11)
basic_ostringstream()     : basic_ostringstream(std::ios_base::out) {}		(2)	(since C++11)
explicit basic_ostringstream     ( const std::basic_string<CharT, Traits, Allocator>& str,       std::ios_base::openmode mode =           std::ios_base::out );		(3)
explicit basic_ostringstream     ( std::basic_string<CharT, Traits, Allocator>&& str,       std::ios_base::openmode mode =           std::ios_base::out );		(4)	(since C++20)
basic_ostringstream( std::ios_base::openmode mode, const Allocator& a );		(5)	(since C++20)
template< class SAlloc > basic_ostringstream( const std::basic_string<CharT, Traits, SAlloc>& str,                      std::ios_base::openmode mode, const Allocator& a );		(6)	(since C++20)
template< class SAlloc > basic_ostringstream( const std::basic_string<CharT, Traits, SAlloc>& str,                      const Allocator& a )     : basic_ostringstream(str, std::ios_base::out, a) {}		(7)	(since C++20)
template< class SAlloc > explicit basic_ostringstream     ( const std::basic_string<CharT, Traits, SAlloc>& str,       std::ios_base::openmode mode =           std::ios_base::out );		(8)	(since C++20)
template< class StringViewLike > explicit basic_ostringstream     ( const StringViewLike& t,       std::ios_base::openmode mode =           std::ios_base::out );		(9)	(since C++26)
template< class StringViewLike > basic_ostringstream( const StringViewLike& t,                      std::ios_base::openmode mode, const Allocator& a );		(10)	(since C++26)
template< class StringViewLike > basic_ostringstream( const StringViewLike& t, const Allocator& a );		(11)	(since C++26)
basic_ostringstream( basic_ostringstream&& other );		(12)	(since C++11)

Constructs new string stream.

Given

• base_type as std::basic_ostream<CharT, Traits>, and
• buf_type as std::basic_stringbuf<CharT, Traits, Allocator>,

the std::basic_ostream base and the exposition-only data member sb are initialized as follows.

Over  load	std::basic_ostream base	sb
(1)	base_type(std::addressof(sb))	buf_type(mode | std::ios_base::out)
(2)		buf_type(std::ios_base::out)
(3)		buf_type(str, mode | std::ios_base::out)
(4)		buf_type(std::move(str), mode | std::ios_base::out)
(5)		buf_type(mode | std::ios_base::out, a)
(6)		buf_type(str, mode | std::ios_base::out, a)
(7)		buf_type(str, std::ios_base::out, a)
(8)		buf_type(str, mode | std::ios_base::out)
(9)	std::addressof(sb)	{t, mode | std::ios_base::out, Allocator()}
(10)		{t, mode | std::ios_base::out, a}
(11)		{t, std::ios_base::out, a}
(12)	move constructed from other's std::basic_ostream base	move constructed from other.sb

8) This overload participates in overload resolution only if std::is_same_v<SAlloc, Allocator> is false.

9-11) These overloads participate in overload resolution only if std::is_convertible_v<const StringViewLike&, std::basic_string_view<CharT, Traits>> is true.

Parameters

str	-	string to use as initial contents of the string stream
t	-	an object (convertible to std::basic_string_view) to use as initial contents of the string stream
a	-	allocator used for allocating the contents of the string stream
mode	-	specifies stream open mode. It is a BitmaskType, the following constants are defined: Constant Explanation app seek to the end of stream before each write binary open in binary mode in open for reading out open for writing trunc discard the contents of the stream when opening ate seek to the end of stream immediately after open noreplace (C++23) open in exclusive mode
other	-	another string stream to use as source

Notes

Construction of one-off basic_ostringstream objects in a tight loop, such as when used for string conversion, may be significantly more costly than calling str() to reuse the same object.

Feature-test macro	Value	Std	Feature
__cpp_lib_sstream_from_string_view	202306L	(C++26)	Interfacing std::stringstreams with std::string_view, (9-11)

Example

Run this code

#include <iostream>
#include <sstream>
 
int main()
{
    // default constructor (input/output stream)
    std::stringstream buf1;
    buf1 << 7;
    int n = 0;
    buf1 >> n;
    std::cout << "buf1 = " << buf1.str() << " n = " << n << '\n';
 
    // input stream
    std::istringstream inbuf("-10");
    inbuf >> n;
    std::cout << "n = " << n << '\n';
 
    // output stream in append mode (C++11)
    std::ostringstream buf2("test", std::ios_base::ate);
    buf2 << '1';
    std::cout << buf2.str() << '\n';
}

Output:

buf1 = 7 n = 7
n = -10
test1

Defect reports

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

DR	Applied to	Behavior as published	Correct behavior
P0935R0	C++11	the default constructor was explicit	made implicit

See also

str	gets or sets the contents of underlying string device object (public member function)
(constructor)	constructs a basic_stringbuf object (public member function of std::basic_stringbuf<CharT,Traits,Allocator>)