Shell, Terminal, Prompt

The terminal is the window, the shell is the program inside it that runs your commands, and the prompt is the line where the shell waits for the next one.

Novice · Unix · Linux · Updated

After this lesson you can

  • Tell the terminal, the shell and the prompt apart
  • Read a prompt such as sam@laptop:~$ and copy a tutorial's command without its $

Key takeaways

  • The terminal is the window you type in. Its font, colors and tabs are the window's settings.
  • The shell is the program in the window that reads each command and runs it. bash is a shell, and so is zsh, the Mac's.
  • The prompt is the shell saying "ready". sam@laptop:~$ shows the user, the computer, the folder you're in, and $.
  • In a tutorial, a $ at the start of a line stands for the prompt. Type what comes after it, not the $.

Tutorials, classmates and coworkers use three words as if they were one: "open your terminal", "type this into the shell", "at the prompt, run…". They're three different things, and knowing which is which tells you where to look when something goes wrong. Is it a setting of the window, the program inside it, or the command you typed?

Think of a restaurant. The dining room is where you sit. The waiter takes your order to the kitchen and brings back what the cooks made. And when the waiter stands at your table with a notepad, asking "What'll it be?", that's your moment to order. In the terminal, those three are the terminal, the shell and the prompt.

The terminal: the window

The terminal is the dining room: the window you type into. On a Mac it's the Terminal app; on Ubuntu it's called Terminal too; on Windows it's Windows Terminal. It shows text and passes on what you type, but it doesn't understand a single command itself.

Its font size, colors and tabs are the window's own settings. Making the text bigger is a terminal setting, and it changes nothing about how commands work. In your textbook, a terminal may be called a terminal emulator: it imitates the screen-and-keyboard terminals that people once used to reach a big shared computer.

The shell: the program that listens

The shell is the waiter. It's a program running inside the terminal that reads each line you type, works out which program you mean, runs it and shows you what it printed. The shell on Linux and in Ubuntu on Windows is bash; on a Mac it's zsh (read "zee shell"), a close cousin. To ask which shell you have:

echo $SHELL

/bin/bash

echo prints what you give it, and $SHELL is read "the value of SHELL": the name of your shell, kept where any program can look it up. On a Mac it prints /bin/zsh. One terminal can hold different shells: Windows Terminal can have Ubuntu's bash in one tab and PowerShell in the next.

The prompt: the shell is ready

The prompt is the waiter with the notepad: the text the shell prints when it's ready for your next command. On Ubuntu it looks like sam@laptop:~$, where laptop stands for your computer's name. Read it left to right:

  • sam: who you are, your user name.
  • @ (read "at"), then laptop: the computer you're on.
  • :, then ~ (read "tilde", or "home"): the folder you're in, here your home folder.
  • $: "ready, type here".

The prompt changes as you move. After cd ~/terminal-practice, it reads sam@laptop:~/terminal-practice$. A Mac's zsh writes its prompt like sam@Sams-MacBook-Air ~ %, with a % where bash has $. And if a prompt ever ends in #, you're the administrator, called root, and every command can change the whole computer, so slow down.

A terminal window labeled "the terminal: the window", with the shell drawn as a program inside it labeled "the shell: reads and runs your commands", and the prompt sam@laptop:~$ with each part labeled: user, computer, folder and the $ that means ready

When there's no prompt, the shell is busy: a command is still running. The Shape of a Command shows how to stop one.

The $ in tutorials

Tutorials often show a command with a $ in front, and what it prints on the next line:

$ pwd
/home/sam

The $ stands for your prompt, so you can tell what to type from what the computer printed back. Copy only what comes after it. Type the $ too, and bash thinks $ is the name of a command:

$ pwd

bash: $: command not found

Check yourself

2 questions to try on the lesson page.

So what

The terminal is the window, the shell runs your commands and the prompt says it's ready. With those three words straight, every tutorial you read makes more sense, and so does every error message.

Key terms

Cheat sheets

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