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

 

C++

Language

Standard Library Headers

Freestanding and hosted implementations

Named requirements

Language support library

Concepts library (C++20)

Diagnostics library

Utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Input/output library

Localizations library

Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

Filesystem library (C++17)

Technical Specifications

 

Input/output library

I/O manipulators

C-style I/O

Buffers

basic_streambuf

basic_filebuf

basic_stringbuf

strstreambuf (deprecated in C++98)

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

istrstream (deprecated in C++98)

ostrstream (deprecated in C++98)

strstream (deprecated in C++98)

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

basic_ostringstream::rdbuf

String operations

basic_ostringstream::str

 

basic_ostringstream() : basic_ostringstream(ios_base::out) { }	(1)	(since C++11)
	(2)
explicit basic_ostringstream( ios_base::openmode mode = ios_base::out );			(until C++11)
explicit basic_ostringstream( ios_base::openmode mode );			(since C++11)
explicit basic_ostringstream( const std::basic_string<CharT,Traits,Allocator>& str,                               ios_base::openmode mode = ios_base::out );		(3)
basic_ostringstream( basic_ostringstream&& other );		(4)	(since C++11)

Constructs new string stream.

1) Default constructor. Constructs new underlying string device with the default open mode

2) Constructs new underlying string device. The underlying basic_stringbuf object is constructed as basic_stringbuf<Char,Traits,Allocator>(mode | ios_base::out).

3) Uses a copy of str as initial contents of the underlying string device. The underlying basic_stringbuf object is constructed as basic_stringbuf<Char,Traits,Allocator>(str, mode | ios_base::out).

4) Move constructor. Constructs the string stream with the state of other using move semantics.

Parameters

str	-	string to use as initial contents of the string stream
mode	-	specifies stream open mode. It is bitmask type, 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
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.

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	default constructor was explicit	made implicit

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

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>)