Beginning with the Terminal

Overview

Teaching: 15 min
Exercises: 0 min

Questions

• How do I navigate in command line?

Objectives

• Discover the terminal

• Use simple commands to navigate your computer in command line

What is the Terminal?

The shell is a program on your computer whose job is to run other programs. Pseudo-synonyms are “terminal”, “command line”, and “console”. There’s a whole StackExchange thread on the differences (What is the difference between Terminal, Console, Shell, and Command Line?), but I don’t find it to be terribly enlightening. Your mileage may vary.

– Jenny Bryan in Happy Git with R

The terminal is a command-line program that let you run other programs.

Why would people use command-line rather than Graphical User Interface? Well one answer is that are more stable that interface, and they tend to crash less (because they don’t have to deal with the graphical part!). Also some computers, like online servers or high performance clusters, are almost only accessible through command-line. So it may useful to familiarize yourself with the shell.

How can I use it?

If you’re on Mac or Linux you should have a program called “Terminal”, if you’re on Windows launch the “Git Bash” application.

Navigating into folders

Once you’ve launched it you’re going to see a black window with a blinking cursor. Welcome to the terminal!

We’re going to go through some basic commands to navigate on your computer.

Because you’re navigating into the files and folders of your computer, it can be useful to know exactly where your are. For this use the pwd command which is short for present working directory. It indicates precisely where your are.

$ pwd

/c/Users/ke76dimu

Slashes / indicate nested folders. Here (on a Windows computer) it shows that I am on the C:/ drive (shorthened in /c/ here) within the ke76dimu Which is in the Users folder.

Whenever you get lost in the command-line, you can always use pwd to remind yourself of where you are.

The list command ls lists the files and folders available in the specified folder.

$ ls

 Contacts/
 Desktop/
 Documents/
 Downloads/
 Favorites/
 Pictures/
 R/
 Searches/
 Videos/
 Zotero/

All the names that finish with a slash / indicate a folder. Depending on type of terminal you are using, the folders can also be represented in another color like in blue.

You can look at what’s inside a folder by adding its names after the command:

$ ls Documents

144101.pdf                                  'My Music'@
'AMF_Unikurse_April 2022.pdf'               'My Videos'@
desktop.ini                                 projects/
R/                                          feature_extraction/                         
'WiSe 2021_22_AMF_Unikurse_filled.pdf'      Livres/
Zoom/                                       'Matthias Material'/

We can see a file 144101.pdf and many folders (like R/) note that folders with spaces in their names are indicated with single quote ‘’ like 'Matthias Material'/.

You can re-check that your working directory hasn’t changed by reusing the pwd command.

$ pwd

/c/Users/ke76dimu

Some files and folders may be special and are not shown by default. To display them we use the -a option of the ls command:

$ ls -a

./
../
.atom/
.bash_history
.bash_profile
.bashrc
.gitconfig
.ssh/
.vim/
.viminfo
Contacts/
Desktop/
Documents/
Downloads/
Favorites/
Pictures/
R/
Searches/
Videos/
Zotero/

You can now see several files and folders that names begin with a dot . like .bashrc and .vim/. We’re not going to detail their usefulness, the important thing to remember is that ls -a gives you a bigger list of files, including hidden files.

To change directory we use the change directory command cd.

Let’s say we want to into the Documents/ folder. We type the cd command followed by the folder name.

$ cd Documents/

Recheck where we are with pwd

$ pwd

/c/Users/ke76dimu/Documents

File and Folder names autocompletion

It can become cumbersome to type entire folder names. That’s why most terminal software offer autocompletion of folder names based on typing the beginning of the name then typing the Tabulation (Tab) key on the keyboard (The one on the left of the top row of letters on your keyboard).

What about if you want to back in a folder that is the parent of your folder? Let’s say we want to go back where we were instead of the Documents/ folder. Well, you can use the special folder name .. which defines the parent folder of the folder you’re in.

$ cd ..

/c/Users/ke76dimu/Documents

With the terminal we can also create folders with the make dirirectory command mkdir.

$ mkdir gitintro
$ cd gitintro
$ pwd

/c/Users/ke76dimu/Documents/gitintro

We’re also going to use a command to create files easily. touch is a command that let you create empty files to edit them afterwards.

$ touch terminal-101.txt
$ ls

terminal-101.txt

Recent commands

Use up and down arrows to navigate the latest commands you launched. You can see the last 1,000 commands passed to the terminal using history. You can also start a reverse search pressing Ctrl + R; start typing to see the latest relevant commands.

Key Points

• Use pwd to show in which folder you are.

• Use ls to list the files of a folder

• Use ls -a to show all files and folders

• Use cd to change the folder

• Use cd .. to go back one folder

• Use mkdir to create a folder

• Use touch to create an empty file