Library / Terminal & command line / Shell
No. 099·noun·also called bash, zsh, PowerShell

Shell

The program inside the terminal that reads each command you type and runs it.

SPECIMEN · DIAGRAM · LAYERS
TerminalThe window: shows text, takes keystrokes
Shellzsh, bash, PowerShell: interprets what you typed
Programsgit, npm, node: do the actual work
Operating systemFiles, processes, network
Definition

What it is

The shell is the interpreter behind the terminal window. When you press Enter, the shell figures out what you meant, runs the right program, and hands you back the result. Common shells are zsh (the Mac default), bash (common on Linux servers), and PowerShell (Windows).

Shells differ in small ways, so a command that works on a Mac might need tweaking on Windows. If an agent's instructions fail on your machine, telling it which shell you use often fixes it.

A shell script is a file of commands saved so they can run in one go.

Say it like a builder

How to ask for it

Vague

“Your instructions don't work on my computer.”

Precise

“I'm on Windows using PowerShell, and the export API_KEY=... line from your instructions fails. Give me the PowerShell equivalent.”

Why it works

Naming your shell explains why the command failed and lets the agent translate it, instead of guessing at the problem.

In the wild

You've seen this in

  • T"zsh" in the title bar of the Mac Terminal
  • FFiles ending in .sh
  • SSetup instructions that say "paste this into your shell"
Usage note

Often confused with

TerminalThe terminal is the window you look at; the shell is the program running inside it.