codex-lv2-may-2025

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Introducing the Shell

The shell is a program that lets you control your computer by typing commands instead of clicking. It may seem unfamiliar at first, but it’s a powerful tool that can save time, reduce errors, and automate repetitive tasks.

In this lesson, you’ll learn what the shell is, how it works, and why it’s useful.

Steps

  1. Understand what a shell is The shell is a program where you type commands. It sends your instructions to the computer and displays the output. Most modern shells use a program called Bash.

  2. Know why you might use it A graphical user interface (GUI) is easy to learn, but not efficient for big or repetitive tasks. For example: If you need to copy the third line of 1,000 text files into a new file, using the mouse would take hours. Using the shell, this can be done in seconds.

  3. Look for the shell prompt When you open the shell, you’ll see a prompt. This is usually a dollar sign ($) that tells you the shell is ready. Example:

    $

    Some prompts include your name or computer name, like:

    nelle@localhost $

    Only type the command, not the $.

  4. Try your first command At the prompt, type:

    ls

    Then press Enter. This lists the files and folders in your current location.

    On a Mac or Linux system, you might see:

    Desktop     Downloads   Movies      Pictures
Documents   Library     Music       Public

    On Windows using Git Bash, you might see:

    'Applications'   'Desktop'   'Documents'   'Downloads'
'Favorites'      'Music'     'Pictures'    'Videos'

  5. Handle mistakes If you type a command that doesn’t exist, the shell will show an error:

    $ ks
ks: command not found

    This usually means you made a typo or the program isn’t installed.

Notes