Introduction to the command-line interface
For readers at home: this chapter is covered in the Your new friend: Command Line video.
It's exciting, right?! You'll write your first line of code in just a few minutes! :)
Let us introduce you to your first new friend: the command line!
The following steps will show you how to use the black window all hackers use. It might look a bit scary at first but really it's just a prompt waiting for commands from you.
Note Please note that throughout this book we use the terms 'directory' and 'folder' interchangeably but they are one and the same thing.
What is the command line?
The window, which is usually called the command line or command-line interface, is a text-based application for viewing, handling, and manipulating files on your computer. It's much like Windows Explorer or Finder on the Mac, but without the graphical interface. Other names for the command line are: cmd, CLI, prompt, console or terminal.
Open the command-line interface
To start some experiments we need to open our command-line interface first.
You now should see a white or black window that is waiting for your commands.
Each command will be prepended by this sign and one space, but you don't have to type it. Your computer will do it for you. :)
Just a small note: in your case there may be something like
Olas-MacBook-Air:~ ola$before the prompt sign, and this is 100% OK.
The part up to and including the
$ or the
> is called the command line prompt, or prompt for short. It prompts you to input something there.
In the tutorial, when we want you to type in a command, we will include the
>, and occasionally more to the left. You can ignore the left part and just type in the command which starts after the prompt.
Your first command (YAY!)
Let's start with something simple. Type this command:
And then hit
enter. This is our result:
$ whoami olasitarska
As you can see, the computer has just printed your username. Neat, huh? :)
Try to type each command; do not copy-paste. You'll remember more this way!
Each operating system has a slightly different set of commands for the command line, so make sure to follow instructions for your operating system. Let's try this, shall we?
It'd be nice to know where are we now, right? Let's see. Type this command and hit
You'll probably see something similar on your machine. Once you open the command line you usually start at your user's home directory.
List files and directories
So what's in it? It'd be cool to find out. Let's see:
Change current directory
Now, let's go to our Desktop directory:
Check if it's really changed:
Here it is!
PRO tip: if you type
cd Dand then hit
tabon your keyboard, the command line will automatically fill in the rest of the name so you can navigate faster. If there is more than one folder starting with "D", hit the
tabbutton twice to get a list of options.
How about creating a practice directory on your desktop? You can do it this way:
This little command will create a folder with the name
practice on your desktop. You can check if it's there just by looking on your Desktop or by running a
dir command! Try it. :)
PRO tip: If you don't want to type the same commands over and over, try pressing the
down arrowon your keyboard to cycle through recently used commands.
A small challenge for you: in your newly created
practice directory, create a directory called
test. (Use the
We don't want to leave a mess, so let's remove everything we did until that point.
First, we need to get back to Desktop:
.. with the
cd command will change your current directory to the parent directory (that is, the directory that contains your current directory).
Check where you are:
Now time to delete the
Attention: Deleting files using
rmis irrecoverable, meaning the deleted files will be gone forever! So be very careful with this command.
Done! To be sure it's actually deleted, let's check it:
That's it for now! You can safely close the command line now. Let's do it the hacker way, alright? :)
Cool, huh? :)
Here is a summary of some useful commands:
|Command (Windows)||Command (Mac OS / Linux)||Description||Example|
|exit||exit||close the window||exit|
|cd||cd||change directory||cd test|
|cd||pwd||show the current directory||cd (Windows) or pwd (Mac OS / Linux)|
|copy||cp||copy file||copy c:\test\test.txt c:\windows\test.txt|
|move||mv||move file||move c:\test\test.txt c:\windows\test.txt|
|mkdir||mkdir||create a new directory||mkdir testdirectory|
|rmdir (or del)||rm||delete a file||del c:\test\test.txt|
|rmdir /S||rm -r||delete a directory||rm -r testdirectory|
These are just a very few of the commands you can run in your command line, but you're not going to use anything more than that today.
If you're curious, ss64.com contains a complete reference of commands for all operating systems.
Let's dive into Python!