basic_ostringstream() : basic_ostringstream(ios_base::out) { }
(1) (since C++11)
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 );
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.


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


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


#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';


buf1 = 7 n = 7
n = -10

See also

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

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