The terminal and the shell

What the terminal is, how a command is built and how to move between folders.

The terminal is a window where you type text commands. The shell (usually bash or zsh) is the program inside it that reads what you type and runs it. Almost everything on a Linux server is done this way, including over SSH.

The prompt

ana@laptop:~$

It shows your user (ana), the machine (laptop) and where you are (~, your home folder). The $ means you are a normal user. A # means you are root, the administrator.

Anatomy of a command

ls -l /var/log
│   │  └── argument: what to act on
│   └── option: changes how it behaves
└── command: what to run

Where am I and what is here?

pwd          # print working directory
ls           # list files
ls -l        # long format: permissions, owner, size, date
ls -la       # also show hidden files (names that start with a dot)
cd /var/log  # go to an absolute path
cd ..        # go up one level
cd ~         # go home
cd -         # go back to the previous folder

Absolute and relative paths

• An absolute path starts at the root /, for example /etc/ssh/sshd_config. It works from anywhere.
• A relative path starts from where you are. . is the current folder and .. is the parent.
• ~ is shorthand for your home folder.

Help is built in

ls --help     # short summary
man ls        # full manual page (press q to quit)

NotePress Tab to complete names, and the up arrow to bring back earlier commands. Both save a lot of typing and mistakes.