C/C++ :: Program That Can Merge Files From Command Line In Li

I have written a C++ program that is supposed to open two text files (prog2a.dat and prog2b.dat) and write the contents of a specified range of lines to an output file (outfile.dat). I wrote a program that based on the example we were given (to take lines 5-15 from the first file and lines 4-12 of the second file and merge them into the output file) works perfectly. However, after asking my professor for some clarification on another part of the assignment, I found out I have not done this correctly. I have the code written so that it will always output the range of lines I mentioned earlier, but the program is actually supposed to allow the user to merge the files from the command line using whatever range they want by typing in the following command:

prog2 in1 5-15 in2 4-12 outfile

But I'm not sure how to tweak my current program to allow this to be done.

Here is the code that I have written, keep in mind that this works properly for the way it is written, but not how it is supposed to work for the purposes of the command line (hopefully that makes sense):

#include <iostream>
#include <fstream>
#include <cstdlib>
using namespace std;
int main() {
// Create output file
std::ofstream outFile("outfile.dat", ios::out);

[Code] .....

Is there any simple way to make this work as I described using the command line? Also, I am supposed to break this up into three files, a header file, the program file, and a test file (the test file contains main() and should close the 3 open files and display any error messages), but I'm getting really confused as to what should go in the header file. I know the header file should contain class definitions and constructors, but don't really know how to make that work for this specific program?