Get/set the associated string object.
  The first syntax returns a copy of the string object currently associated with the internal buffer.
  The second syntax sets a new value for the string object associated with the buffer.
  The buffer of a stringstream is usually associated with an STL string object.

Parameters.

s

string object to be associated with the stream.

Return Value.
  The second syntax returns a copy of the string object currently associated with the stream's buffer.

Example.

// ostringstream::str
#include <iostream>
#include <sstream>
#include <string>
using namespace std;

int main () {

  ostringstream oss;
  string mystr;

  oss << "Sample string";
  mystr=oss.str();

  cout << mystr;

  return 0;
}

Basic template member declaration ( basic_ostringstream<charT,traits,Allocator> ):

basic_string<charT,traits,Allocator> str () const; void str (const basic_string<charT,traits,Allocator> & s );

See also.
  (constructor)
  ostringstream class