#include <iostream>
#include <string.h>

using namespace std;

void Usage(char * name);

int main(int argc, char * argv[]) {
    string greeting{"Hello World"};
    bool doHelp{false};

    int i{1};

    while (i < argc) {
        if (!strcmp(argv[i],"-h") or !strcmp(argv[i],  "--help")) {
            doHelp = true;
            ++i;
        } else if (!strcmp(argv[i],"-G") or !strcmp(argv[i],  "--greeting")) {
            ++i;
            if (i < argc) {
                greeting = argv[i];
                ++i;
            } else {
                cerr << "Error: -g, --greeting require an additional arg"
                     << endl;
                doHelp = true; 
            }
        } else {
            cerr <<"Error: " <<  argv[i] << " is unknown" << endl;
            doHelp = true;
            ++i;
        }
    }

    if (doHelp) {
       Usage(argv[0]);
    }

    cout << greeting << endl;
    return 0;
}

void Usage(char * name){
   cout << name << " usage: " << endl;
   cout << "\t -h, --help ........ Print Help" << endl;
   cout << "\t -G, --greeting .... Change the greeting, next arg is greeting." << endl;

   cout << endl;
}