TerminalEmulator

Introduction

TerminalEmulator turn any backend script into a pure-Javascript terminal interface on-demand, on Linux, MacOS, and Windows. Handle user or agent input by passing a handler, or reading and writing to a Wirteable stream. It simulates the look and feel of a shell including proper formatting of stdout, stderr, and terminal resets, including a typical prompt like "user@user:~$" on new inputs.

Note: This library doesn't actually handle the shell commands, it returns the raw input of the user or agent prompt for your application to handle and return to the terminal's stdout or stderr.

Note: This library is standalone, but is intended to be used with @ai-tools/virtual-shell, which is a fully emulated unix terminal command handler (the thing that handles commens) in Javascript that runs completely in memory with it's own virtual file system, and can be used as the input handler for commands given to this terminal-emulator, allowing you to handle typical unix commands like ls, cd, cat, rm, etc. Used together and they essentially create a fully virtualized container that a user or AI agent can write, build, and test code in that can be interfaced with an emulated terminal - all in Javascript and all in memory. This is similar to Stackblitz but with access to native OS APIs.

Features

• Interactive Interface: Customizable terminal prompts and real-time user interaction.
• Flexible Input Handling: Process user inputs with user-defined handler functions that can return strings, objects, or errors.
• Stream Subscriptions: Capture and display external stdout and stderr streams.
• Error Management: Gracefully handle and display error messages.
• Input History: Maintain a history of user inputs for easy navigation.
• Terminal Control: Manage user and directory settings, clear the terminal, and handle interrupt signals.

Installation

You can install TerminalEmulator via npm:

npm install @ai-tools/terminal-emulator

Or using Yarn:

yarn add @ai-tools/terminal-emulator

Usage

Basic Example

// Import the TerminalEmulator class
import TerminalEmulator from '@ai-tools/terminal-emulator';

// Define an input handler function
const inputHandler = (input: string) => {
  if (input.startsWith('error')) {
    return new Error('This is an error message.'); // Return an error object
  }
  if (input === 'object') {
    return {
      key1: 'value1',
      key2: 'value2',
      key3: 'This is a long value that will exceed the 80 character limit and should be wrapped accordingly.',
    }; // Return a plain object
  }
  return `You typed: ${input}`; // Return a string for stdout
};

// Create an instance of TerminalEmulator
const terminal = new TerminalEmulator('user', '/home/user', inputHandler);

// Start the terminal emulator
terminal.start();

API Reference

Table of Contents

• Constructor
• Public Methods
  • start()
  • clearTerminal()
  • exit()
  • setUser(user: string)
  • setCurrentDirectory(directory: string)
  • subscribeStdout(stream: Writable)
  • subscribeStderr(stream: Writable)

Constructor

new TerminalEmulator(
  user?: string,
  currentDirectory?: string,
  inputHandler?: InputHandler
)

Parameters:

• user (string, optional): The user name for the terminal prompt. Defaults to 'guest'.
  • Example: 'admin'
• currentDirectory (string, optional): The current directory for the terminal prompt. Defaults to '/'.
  • Example: '/home/user'
• inputHandler (InputHandler, optional): A function to handle user input. It receives the input string and returns a response (string, object, Error, or undefined).

  • Example:

    const inputHandler = (input: string) => `You entered: ${input}`;

Public Methods

start()

Starts the terminal emulator, displaying the prompt for user input.

start(): void

clearTerminal()

Clears the terminal screen and resets the input history.

clearTerminal(): void

exit()

Exits the terminal emulator gracefully.

exit(): void

setUser(user: string)

Sets the user name for the terminal prompt.

setUser(user: string): void

Parameters:

• user (string): The new user name to display in the prompt.
  • Example: terminal.setUser('newUser');

setCurrentDirectory(directory: string)

Sets the current directory for the terminal prompt.

setCurrentDirectory(directory: string): void

Parameters:

• directory (string): The new current directory to display in the prompt.
  • Example: terminal.setCurrentDirectory('/var/log');

subscribeStdout(stream: Writable)

Subscribes a writable stream to receive stdout messages in the terminal. This allows the terminal emulator to capture and display output from external sources.

subscribeStdout(stream: Writable): void

Parameters:

• stream (Writable): The writable stream to subscribe to for stdout messages.

  • Example:

    import { Writable } from 'stream';
    const outputStream = new Writable({
      write(chunk, encoding, callback) {
        console.log(chunk.toString());
        callback();
      }
    });
    terminal.subscribeStdout(outputStream);

subscribeStderr(stream: Writable)

Subscribes a writable stream to receive stderr messages in the terminal. This allows the terminal emulator to capture and display error outputs from external sources.

subscribeStderr(stream: Writable): void

Parameters:

• stream (Writable): The writable stream to subscribe to for stderr messages.

  • Example:

    const errorStream = new Writable({
      write(chunk, encoding, callback) {
        console.error(chunk.toString());
        callback();
      }
    });
    terminal.subscribeStderr(errorStream);

License

This project is licensed under the MIT License.