Finding your way around the terminal

The terminal is a window where you talk to the computer by typing text. The program that reads and runs your commands is called the shell: the most common one on Linux servers is bash, and macOS uses zsh by default (the commands in this course work in both). On Windows, people generally use WSL (an integrated Linux) or Git Bash to get the same commands.

Why use it when graphical interfaces exist? Because servers often have no screen, because many tools (Git, Python, npm, Docker) are driven from the command line, and because a command can be automated in a script.

The prompt and the anatomy of a command

The prompt looks like lea@portable:~/projets$. It shows the user, the machine, the current directory, then $: the shell is waiting for your command.

ls -l --all Documents
# ^   ^   ^      ^
# |   |   |      argument: what to act on
# |   |   long option
# |   short option
# command name

Options change the behavior (often -x in short form, --word in long form). Short options can be combined: ls -la is equivalent to ls -l -a.

The directory tree

Files are organized as a tree. On Linux and macOS, everything starts from the root /. Your home directory is for example /home/lea (Linux) or /Users/lea (macOS), abbreviated ~.

Navigating

pwd                 # print working directory: where am I?
# /home/lea

ls                  # lists the contents of the current directory
ls -l               # long format: permissions, size, date
ls -a               # includes hidden files (starting with a dot)

cd projets          # enters the projets subdirectory
cd ..               # goes up to the parent directory
cd ~                # returns to the home directory (cd alone does the same)
cd -                # goes back to the previous directory

Absolute and relative paths

• An absolute path starts with / and is valid everywhere: /home/lea/projets/site.
• A relative path starts from the current directory: from /home/lea, projets/site refers to the same directory.
• . refers to the current directory and .. to the parent: ../photos means “the photos directory next to me”.

If a name contains spaces, wrap it in quotes: cd "Mes documents".

Three habits that save time

1. Tab automatically completes file and command names. Pressing it twice shows the possibilities.
2. The up and down arrows recall previous commands; history lists them.
3. man ls opens the manual for a command (press q to quit); ls --help gives a summary.

And if a command seems stuck, Ctrl+C interrupts it.