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Terminal basics

This chapter covers the terminal basics required for the tutorial. If you're already comfortable with the command line, feel free to skip it.

What is the terminal?

The terminal is a text-based application for sending commands to your operating system. It's also known as a "console" or "shell".

The prompt

The prompt is the text that appears when the terminal is ready for your next command. It often ends with a $ or % sign.

[username@hostname ~]$

Entering commands

To run a command, type it and press Enter. The first word is the program's name, and subsequent words are its arguments.

For example, the echo program prints its arguments:

$ echo Hello, terminal!
Hello, terminal!

The first word is the program to run. The terminal will find a program called echo on your computer and run it with the two arguments Hello, and terminal!. The program is free to interpret these arguments however it wants. The program called echo happens to simply print its arguments back to the terminal:

The current working directory

The current working directory (CWD) is your current location in the filesystem. Many commands behave differently depending on your CWD.

Use cd ("change directory") to move to a different directory and pwd ("print working directory") to see your current location. The CWD is often shown in the prompt.

[username@hostname ~]$ cd Downloads
[username@hostname Downloads]$ pwd
/home/username/Downloads

The ~ character is a shorthand for your home directory.

Key takeaway: Always be aware of your current working directory. If a command behaves unexpectedly, you might be in the wrong directory.

Copy-pasting commands

This tutorial has many commands for you to copy. You can copy-paste multi-line commands without issue.

  • On Linux/Windows, use Ctrl+Shift+C/V.
  • On Mac, Command+C/V works as usual.

If you accidentally use Ctrl+V on Linux/Windows, you'll see strange characters (^[[200~...). Just press Enter to get a fresh prompt and try again.

Lines starting with a pound sign (#) are comments and are ignored by the terminal.

You can practice by copy-pasting the following command into your terminal:

# Here are some example comments:
#
# This is the program being run.
# |
# |  This is the start of the first argument.
# |  |
# |  |      This is the start of the second argument.
# v  v      v
echo Hello, terminal! # Placing a comment next to a command is also allowed.

Redirection

By default, programs print to "standard out" (stdout), which is your terminal. You can redirect stdout to a file using the > operator, which overwrites the file.

echo "bread, onions, tea" > groceries.txt

To append to a file instead, use the >> operator.

Pagers

A pager is a program that displays large amounts of text one screen at a time. Some commands, including jj, will automatically use a pager for long output.

  • Press q to quit.
  • Use arrow keys or page up/down to navigate.
  • Press / to start a search, and use n/N to find the next/previous match.

If you see a colon : at the bottom-left of your terminal, you are likely in a pager.

Variables and the environment

While we often refer to the "terminal" as a whole, it's actually the shell (the program interpreting your commands) that provides scripting features, like variables.

$ my_name=Alice
$ echo Hello, $my_name!
Hello, Alice!

To make a variable accessible to programs you run, you must export it into the environment. These are called environment variables. By convention, their names are uppercase.

export MY_NAME=Alice

The PATH variable

PATH is a special environment variable. It contains a colon-separated list of directories where the terminal searches for programs.

$ echo $PATH
/home/username/.local/bin:/usr/local/bin:/usr/bin

If you try to run a program and get a "No such file or directory" error, the program might not be in a directory listed in PATH. You can add a new directory to PATH like this:

export PATH="/path/to/my-programs:$PATH"

If you mess up your PATH, the easiest fix is to close the terminal and open a new one.

Startup scripts

Changes to environment variables like PATH only last for the current session. To make them permanent, add the export command to a startup script, which runs every time you open a new terminal.

The script's name depends on your shell. Find your shell by running echo $SHELL.

  • For bash, edit ~/.bashrc.
  • For zsh, edit ~/.zshrc.

You can view your script's content with cat ~/.bashrc (or ~/.zshrc).

Now you know the basics of the terminal ! 🎉

That's enough terminal knowledge to get you through this tutorial. Don't hesitate to come back and review this chapter if you need a refresher.