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What Is the Command Line?

Set Up a Place to Practice Safely

skill transfers between systems at the level of ideas rather than spelling. Find out where you are, look before you change anything, give the command the right path, and check the result afterward. Those four habits hold on every system you will ever work on.

The command names and the path spelling do not transfer, and that is the one thing the next chapter has to handle for you.

The lessons follow your computer

Where a command differs between systems, the next chapter highlights the version that matches your computer: PowerShell on Windows, and a -style on and . Tell the course which system you use in your profile. The site remembers your choice, and you can change it if you move to another machine.

Your highlighted commands will use the Bash route taught in this course.

You may still compare the other branches. The spelling changes; the operation and the evidence you check do not.

Two people follow the same lesson, one on Windows and one on a Mac, and their commands do not look alike. What is actually different?

Two places to practice

The next chapter puts a beside the lesson, with a seeded practice project at /workspace. That is where the graded exercises happen, and nothing there can hurt files on your own computer. The hosted Windows route runs real PowerShell over the hosted /workspace tree; PowerShell on your own Windows machine uses ordinary Windows paths instead.

Prepare a disposable location on your own computer

A few steps ask you to work on your own machine rather than in the browser. Use the computer-fundamentals-practice directory you made in the previous chapter. If it is gone, rebuild it with your file manager:

computer-fundamentals-practice/
├── README.txt
├── archive/
├── data/
└── notes/

Open README.txt and check it says Practice workspace. That one line is how you tell this directory apart from an empty one with the same name somewhere else.

Do not practice in a drive root, a filesystem root, a system directory, a code repository, or anywhere holding work you care about. Do not use administrator or sudo access for any of it. If this is a managed computer and you cannot create the directory, use somewhere your administrator has approved.

Preview, verify, recover

Every exercise in the next chapter follows the same five steps:

  1. Orient. Confirm the working directory before acting.

  2. Preview. List the target and read the command before it changes anything.

  3. Change one thing. Inside the disposable directory.

  4. Verify. List or read the result immediately.

  5. Recover. If it went wrong, stop and use the lesson’s recovery route or rebuild the tree.

Safety in this course comes from working on disposable files with a known starting shape. The lesson that introduces removal will give that operation its own boundaries before you use it.

You copied a command from a forum. It contains an option you do not recognize and appears to remove files. What is the safest next action?

You have a harmless place to work and a routine that governs every change you are about to make. Next, open a terminal and ask it one question that changes nothing.