string line = "hello, world, bye";
char * pch = strtok(line.c_str(),",");

error: invalid conversion from ‘const char*’ to ‘char*’
error: initializing argument 1 of ‘char* strtok(char*, const char*)’

std::string::size_type pos = line.find_first_of(',');
std::string token = pos.substr(0, pos);

istringstream is(line);
string part;
while (getline(is, part, ','))
  cout << part << endl;

std::vector<char> buffer(line.c_str(), line.c_str()+line.size()+1);
char * pch = strtok(&buffer[0], ",");

std::stringstream ss(line);
std::string token;
std::readline(ss, token, ',');

std::string token(line, 0, line.find(','));