std::basic_ostringstream::str(3)

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>)