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() &&; (1) (3) (since C++20)
void str( const std::basic_string<CharT,Traits,Allocator>& s (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)

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));.

Parameters

s - 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.
4-6) (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.

Example

// Run this code

#include <sstream>
#include <iostream>
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"