How to get file extension from string in C++

#include <iostream>#include<string>int main(){  std::string fn = "filename.conf";  if(fn.substr(fn.find_last_of(".") + 1) == "conf") {    std::cout << "Yes..." << std::endl;  } else {    std::cout << "No..." << std::endl;  }}

get prefix

 ofstream file2;
 string headerFilename = string(argv[2]);
 string outputPrefix = headerFilename.substr(0,headerFilename.find_first_of("."));