argparse.cxx

#include<iostream>
#include<stdexcept>
#include<string>

void print_usage() {
  std::cout << "usage: test [args...]\n"
            << '\n'
            << "  help     display this message and exit\n"
            << "  x <int>  set x\n";
}

int main(int argc, char* argv[]) {
  int x = 0;
  for (int i = 1; i < argc; ++i) {
    // possible uncaught exception
    std::string key = std::string(argv[i]);
    if ( key == "help" ) {
      if (i == 1) {
        print_usage();
        return 0;
      }
    } else if ( key == "x" ) {
      ++i;
      // possible uncaught exception
      std::string value = std::string(argv[i]);
      try {
        x = std::stoi(value);
      } catch (const std::invalid_argument& e) {
        std::cout << value << " is not a valid integer\n\n";
        print_usage();
        return 1;
      }
    } else {
      std::cout << "invalid argument: " << key << "\n\n";
      print_usage();
      return 1;
    }
  }
  std::cout << "x = " << x << "\n";
  return 0;
}