What is a command shell?

Many people use the terms command shell, command-line tool, and terminal interchangeably, which can be confusing. This article explains the difference between these concepts and provides examples of each.

A command shell is an interactive command-line interface for managing a computer, also known as a Read-Eval-Print Loop (REPL).

A shell takes input from the keyboard, evaluates that input, and executes the input as a shell command or forwards the input to the operating system to be executed. Most shells can also read commands from a script file, and can include programming features like variables, flow control, and functions.

Types of command shells

There are two main types of command shells:

• General purpose command shells

  General purpose command shells provide are designed to work with the operating system and allow you to run any command that the operating system supports. They also include shell-specific commands and programming features. The following list contains some examples of general purpose command shells:

  • PowerShell
  • Windows Command Shell
  • bash - popular on Linux
  • zsh - popular on macOS

• Utility command shells

  Utility command shells are designed to work with specific applications or services. These shells can only run commands that are specific to the application or service. Some utility shells support running commands from a batch script, but don't include programming features. Usually, these shells can only be used interactively.

  • AI Shell - An interactive-only shell used to communicate with AI services such as Azure OpenAI.
  • netsh - Network shell (netsh) is a command-line utility that allows you to configure and display the status of various network components on Windows. It's both a command-line tool and a command shell. It also supports running commands from a script file.

Command-line tools

A command-line tool is a standalone program that you run from a command shell. Command-line tools are typically designed to perform a specific task, such as managing files, configuring settings, or querying for information. Command-line tools can be used in any shell that supports running external programs.

• Azure CLI - a collection of command-line tools for managing Azure resources that can be run in any supported shell.
• Azure PowerShell - a collection of PowerShell modules for managing Azure resources that can be run in any supported version of PowerShell.
• OpenSSH for Windows - includes a command-line client and a server that provides secure communication over a network.
• Windows Commands - a collection of command-line tools that are built into Windows.

In general, command-line tools don't provide a command shell (REPL) interface. The netsh command in Windows is an exception, as it's both a command-line tool and an interactive command shell.

Terminals

A terminal is an application that provides a text-based window for hosting command shells. Some terminals are designed to work with a specific shell, while others can host multiple shells. They can also include advanced features such as:

• Ability to create multiple panes within a single window
• Ability to create multiple tabs to host multiple shells
• Ability to change color schemes and fonts
• Support for copy and paste operations

The following list contains some examples of terminal applications:

• Windows Terminal - a modern terminal application for Windows that can host multiple shells.
• Windows Console Host - the default host application on Windows for text-based applications. It can also host the Windows Command Shell or PowerShell.
• Terminal for macOS - the default terminal application on macOS that can host the bash or zsh shell.
• iTerm2 for macOS - a popular 3rd-party terminal application for macOS.
• Azure Cloud Shell - a browser-based terminal application hosted in Microsoft Azure. Azure Cloud shell gives you the choice of using bash or PowerShell. Each shell comes preconfigured with many command-line tools for managing Azure resources.