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

 

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)
std::basic_string<CharT, Traits, Allocator> str() const;			(until C++20)
std::basic_string<CharT, Traits, Allocator> str() const&;			(since C++20)
template< class SAlloc > std::basic_string<CharT, Traits, SAlloc> str( const SAlloc& a ) const;		(2)	(since C++20)
std::basic_string<CharT, Traits, Allocator> str() &&;		(3)	(since C++20)
void str( const std::basic_string<CharT, Traits, Allocator>& s );		(4)
template< class SAlloc > void str( const std::basic_string<CharT, Traits, SAlloc>& s );		(5)	(since C++20)
void str( std::basic_string<CharT, Traits, Allocator>&& s );		(6)	(since C++20)
template< class StringViewLike > void str( const StringViewLike& t );		(7)	(since C++26)

Manages the contents of the underlying string object.

1) Returns a copy of the underlying string. Equivalent to return rdbuf()->str();.

2) Returns a copy of the underlying string, using a as allocator. Equivalent to return rdbuf()->str(a);.

3) Returns a string move-constructed from the underlying string. Equivalent to return std::move(*rdbuf()).str();.

4,5) Replaces the contents of the underlying string. Equivalent to rdbuf()->str(s);.

6) Replaces the contents of the underlying string. Equivalent to rdbuf()->str(std::move(s));.

7) Replaces the contents of the underlying string. Equivalent to rdbuf()->str(t);.

This overload participates in overload resolution only if is_convertible_v<const T&, basic_string_view<charT, traits>> is true.

Parameters

s	-	new contents of the underlying string
t	-	an object (convertible to std::basic_string_view) to use as the new contents of the underlying string
a	-	allocator used to construct the returned string

Return value

1,2) A copy of the underlying string object.

3) A string move-constructed from the underlying string object.

4-7) (none)

Notes

The copy of the underlying string returned by str is a temporary object that will be destructed at the end of the expression, so directly calling c_str() on the result of str() (for example in auto *ptr = out.str().c_str();) results in a dangling pointer.

Feature-test macro	Value	Std	Feature
__cpp_lib_sstream_from_string_view	202306L	(C++26)	Interfacing std::stringstreams with std::string_view, (7)

Example

Run this code

#include <iostream>
#include <sstream>
 
int main()
{
    int n;
 
    std::istringstream in; // could also use in("1 2")
    in.str("1 2");
    in >> n;
    std::cout << "After reading the first int from \"1 2\", the int is "
              << n << ", str() = \"" << in.str() << "\"\n";
 
    std::ostringstream out("1 2");
    out << 3;
    std::cout << "After writing the int '3' to output stream \"1 2\""
              << ", str() = \"" << out.str() << "\"\n";
 
    std::ostringstream ate("1 2", std::ios_base::ate);
    ate << 3;
    std::cout << "After writing the int '3' to append stream \"1 2\""
              << ", str() = \"" << ate.str() << "\"\n";
}

Output:

After reading the first int from "1 2", the int is 1, str() = "1 2"
After writing the int '3' to output stream "1 2", str() = "3 2"
After writing the int '3' to append stream "1 2", str() = "1 23"

See also

rdbuf	returns the underlying raw string device object (public member function)
str	replaces or obtains a copy of the associated character string (public member function of std::basic_stringbuf<CharT,Traits,Allocator>)