NAME¶

std::basic_ostringstream::str - std::basic_ostringstream::str

Synopsis¶

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 (2) (since C++20)
) const;
std::basic_string<CharT, Traits, Allocator> str() &&; (3) (since C++20)
void str( const std::basic_string<CharT, Traits, Allocator>& s (1) (4)
);
template< class SAlloc > (5) (since C++20)
void str( const std::basic_string<CharT, Traits, SAlloc>& s );
void str( std::basic_string<CharT, Traits, Allocator>&& s ); (6) (since C++20)
template< class StringViewLike > (7) (since C++26)
void str( const StringViewLike& t );

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