Traversing the filesystem

Up until now, we always provided our code with the static location of a certain file. Alas, the real world is seldom so predictable, and some digging is going to be necessary when dealing with data scattered throughout different folders.

walkdir helps us with this by abstracting away the intricacies and inconsistencies of operating systems' representation of the filesystem by unifying them under one common API, which we are going to learn about in this recipe.