This week's book giveaway is in the OO, Patterns, UML and Refactoring forum. We're giving away four copies of Refactoring for Software Design Smells: Managing Technical Debt and have Girish Suryanarayana, Ganesh Samarthyam & Tushar Sharma on-line! See this thread for details.
If you want to do it like the link you'll need a GUI.
If you want to keep it as CLI, print out the files side by side with some marker to show lines that don't match then add a print statement to the if statement that compares the lines for equality. You will need to change the chars you insert between the two concatenated lines so you can see which lines are not the same.