How do you convert string to c_str() in this situation?

Question

Possible Duplicate:
Convert std::string to const char* or char*

My code is this

#include <iostream>
#include <fstream>

using namespace std;

string mapChange(int side, string oldMap);

int main(){

  string createMapName;
  string createMapNameData [10];
  int featureSelect;

  cout << "(1)Game or (2)Mapmaker";
  cin >> featureSelect;

  if(featureSelect == 2)
  {
    cout << "Name of Map?";
    cin >> createMapName;
    ofstream mapName;
    mapName.open (createMapName);
    mapName << createMapNameData[0] << endl;
  }
  return 0;
}

string mapChange(int side, string oldMap){

    string newMap;
    if(oldMap == "Test")
    {
      cout << "Map Found :D";
    }
    else
    {
      cout << "ERROR MAP NOT FOUND, PLEASE REINSTALL.";
    }
    return newMap;
}

How do I use a c_str instread of string on line 15 i.e. how do I convert string to c_str()? Please help, Lijrobert