#include <sstream>
  void str( string s );
  string str();

The function str() can be used in two ways. First, it can be used to get a copy of the string that is being manipulated by the current stream string. This is most useful with output strings. For example:

  ostringstream stream1;
  stream1 << "Testing!" << endl;
  cout << stream1.str();

Second, str() can be used to copy a string into the stream. This is most useful with input strings. For example:

  istringstream stream1;
  string string1 = "25";
  stream1.str(string1);

str(), along with clear(), is also handy when you need to clear the stream so that it can be reused:

  istringstream stream1;
  float num;

  // use it once
  string string1 = "25 1 3.235\n1111111\n222222";
  stream1.str(string1);
  while( stream1 >> num ) cout << "num: " << num << endl;  // displays numbers, one per line

  // use the same string stream again with clear() and str()
  string string2 = "1 2 3 4 5  6 7 8 9 10";
  stream1.clear();
  stream1.str(string2);

  while( stream1 >> num ) cout << "num: " << num << endl;  // displays numbers, one per line