Convert string to Cstring From http://stackoverflow.com/questions/11821491/converting-string-to-cstring-in-c

string_to_cstr.cpp

vector<char> toVector( const std::string& s ) {
  string s = "apple";  
  vector<char> v(s.size()+1);
  memcpy( &v.front(), s.c_str(), s.size() + 1 );
  return v;
}
vector<char> v = toVector(std::string("apple"));

// what you were looking for (mutable)
char* c = v.data();