Hacking Team: File Paths

Welcome to lesson number one Hacking Team! In this lesson, we’ll go over the basics of paths and how to navigate around a system.

A Tree of Files

Think of your filesystem like an upside-down tree. At the top is the root of the tree. Each branch that grows from the root may grow subsequent branches ad infinitum or end in a leaf. In this example, branches represent directories and leaves represent files. If you are unfamiliar with the term “directory”, just think of it like a “folder” in Windows File Explorer.

Many tree-related analogs to filesystem elements persist into real terminology. For example, the directory which holds all others and has no parent directory is actually called the root directory. “Tree” is another–tree is a command which will display the branching structure of a given directory.

Below is an example of a basic filesystem visualized as a tree.

Working Directory

When traversing the file system, we will always be “in” a directory. This is called the current working directory. Imagine opening a folder in File Explorer. That folder becomes the new working directory. Usually, the working directory starts as your user’s home folder.

Types of Paths

The location of anything—directory or file—is called a path. There are two ways to write these paths. One is determinant on your working directory; these are relative paths. The other is not, and will refer to the same file or directory regardless of your working directory; these are absolute paths.

In other words, absolute paths are like giving your friend an address to get to your house, while relative paths are like giving directions. Your friend can find their way to your house from anywhere, but your directions to your friend must take into consideration their location.

Consider the example file tree graphic again.

Absolute Paths

Let’s start with absolute paths. Every absolute path starts at the root directory, represented by a forward slash at the start of the path: /. After that, we separate the name of every branch we go down until we reach our target. For example, the absolute path to config1.txt is /home/etc/config1.txt.

Try some of the questions below!

Relative Paths

Now, onwards with relative paths! Relative paths are directions to a file or directory starting from your working directory. For example, if the working directory is /home/, the relative path to email.txt is alice/email.txt.

Try some yourself!

Going Back

If you did the last practice question for relative paths, you may have noticed you needed to go back up the tree instead of down like normal. This can be done with the special .. directory. The double-dot directory is actually its parent’s parent directory. In simpler terms, it takes you one directory up.

Let’s practice more relative paths using the double-dot.

Other Quirks

Just like the double-dot directory (..), there are many other tricks to working efficiently with paths.

On Linux, MacOS, and similar systems, tilde (~) is a shortcut for the home directory of the logged-in user. So, if you were logged in as Bob, ~ would be the same as /home/bob/.

Additionally, there is a single-dot directory (.) that represents the current working directory. For example, if the working directory is /home/alice/, . would refer to the exact same directory—/home/alice/. At first glance this seems useless, but it has some important advanced use cases.

Conclusion

This lesson covered just the prerequisite basics of paths so we can jump into competitions as soon as possible. We will learn the rest through experience—the best teacher.