# Directories & files in Linux

Linux has a very specific file structure, with certain folders containing certain information. But what are these folders, and how do you traverse them in the command line?

| Location         | Purpose                                                                                                                                                    | Aliases |
| ---------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------- | ------- |
| `/`              | The **root** directory in Linux, where all folders are stored. Think of this as the equivalent of the *My Computer* folder on Windows                      | N/A     |
| `/home/USERNAME` | Where all of your personal files are stored. This usually contains `Desktop`, `Downloads`, `Documents`etc                                                  | `~/`    |
| `.`              | A representation of the current directory. For example, if you have a document called `README.md` in your current folder, it could be called `./README.md` | N/A     |
| `..`             | Similar to `.`, but representing the upper directory. For example, if you wanted to go to the upper directory, you could use `cd ..`                       | N/A     |

### LS

`ls` is the command often taught first to Linux beginners, as it it easy to use and provides information for use in other commands. `ls` lists the contents of a directory, showing all files & folders inside. Here are some examples of regular `ls` usage:

| Command  | Usage                                                                                                               |
| -------- | ------------------------------------------------------------------------------------------------------------------- |
| `ls`     | Lists the contents of the current directory                                                                         |
| `ls -a`  | Lists the contents of the current directory, including files beginning with `.`                                     |
| `ls -l`  | Lists the contents of the current directory, with additional information such as date modified and user permissions |
| `ls DIR` | Lists the contents of the directory DIR                                                                             |
| `ls ..`  | Lists the contents of the parent directory                                                                          |

Some common `ls` flags are:

| Flag    | Shorthand | Description                                                                                                                                |
| ------- | --------- | ------------------------------------------------------------------------------------------------------------------------------------------ |
| `--all` | `-a`      | Do not ignore entries starting with `.` (*dotfiles* are files and folders that are intentionally hidden, usually to reduce clutter*)* |
| `-l`    | `-l`      | Display data in a *long* format                                                                                                            |
| `-S`    | `-S`      | Sort by size, largest first                                                                                                                |

{% hint style="info" %}
Remember that you can stack flags! Try looking into some of the options for each command, and see what outputs you can produce.
{% endhint %}

### CD

One of the commands you will use most often in Linux is `cd`. CD stands for **C**hange **D**irectory, which helps the user to move their current directory. Here are some examples of regular `cd` usage:

| Command  | Usage                                                                                                                                    |
| -------- | ---------------------------------------------------------------------------------------------------------------------------------------- |
| `cd`     | Moves to the home directory                                                                                                              |
| `cd ..`  | Moves to the parent directory                                                                                                            |
| `cd -`   | Moves to the last directory. For example, you can use `cd /` to enter the root directory and `cd -` to return to your previous directory |
| `cd DIR` | Moves to the directory DIR                                                                                                               |

### MKDIR

To create a folder in Linux, you can use the command `mkdir`. This command is relatively simple, with only basic application:

| Command        | Usage                                                         |
| -------------- | ------------------------------------------------------------- |
| `mkdir DIR`    | Creates an empty directory called DIR                         |
| `mkdir ../DIR` | Creates an empty directory called DIR in the parent directory |

### TOUCH

Similar to `mkdir`, `touch` is a command that creates an empty file at the specified location. Again, this command only has basic applications:

| Command             | Usage                                                           |
| ------------------- | --------------------------------------------------------------- |
| `touch test.txt`    | Creates an empty file called `test.txt`                         |
| `touch ../test.txt` | Creates an empty file called `test.txt` in the parent directory |

{% hint style="info" %}
Keep in mind that most of these commands take a path as input, and therefore can be more than just one part. For example, you can use `cd ../../..` to travel many directories at once, or `mkdir ~/test` to create an empty directory in your `home`. Try playing around with more complicated directory usage now, as it will assist you later on with more complex folder structures!
{% endhint %}