@oclif/core

What is @oclif/core?

The @oclif/core npm package is a framework for building command-line interfaces (CLIs) in Node.js. It provides a powerful set of tools to develop sophisticated CLIs with features such as argument parsing, command structure, and plugin support. This package is part of the Open CLI Framework (OCLIF) developed by Heroku.

What are @oclif/core's main functionalities?

Command Creation

This feature allows developers to create custom commands for their CLI. The code sample demonstrates how to define a simple command that accepts a name as a flag and prints a greeting message.

const {Command, flags} = require('@oclif/core');

class MyCommand extends Command {
  async run() {
    const {flags} = await this.parse(MyCommand);
    console.log(`Hello, ${flags.name}!`);
  }
}

MyCommand.description = 'Describe the command here';

MyCommand.flags = {
  name: flags.string({char: 'n', description: 'name to print'}),
};

module.exports = MyCommand;

Argument Parsing

This feature simplifies the process of parsing arguments passed to commands. The code sample shows how to create a command that echoes a message passed as an argument.

const {Command, flags} = require('@oclif/core');

class EchoCommand extends Command {
  async run() {
    const {args} = await this.parse(EchoCommand);
    console.log(`Echoing: ${args.message}`);
  }
}

EchoCommand.args = [{name: 'message'}];

module.exports = EchoCommand;

Plugin Support

OCLIF supports plugins to extend the functionality of your CLI. This code sample demonstrates how to define a simple plugin that includes a custom command.

const {Command, Plugin} = require('@oclif/core');

class MyPlugin extends Plugin {
  constructor(root, config) {
    super(root, config);
    this.name = 'my-plugin';
  }

  commands = [require('./commands/my-command')];
}

module.exports = MyPlugin;

Other packages similar to @oclif/core

commander

Commander is a lightweight, expressive, and powerful command-line framework for Node.js. It provides a simpler API compared to @oclif/core but lacks some of the advanced features such as plugin support and automatic help generation.

yargs

Yargs helps you build interactive command-line tools, by parsing arguments and generating an elegant user interface. It's more focused on parsing arguments and providing a fluent API, whereas @oclif/core offers a more structured approach to building CLIs with support for plugins and multi-command CLIs.

vorpal

Vorpal is a framework for building immersive CLI applications in Node. It offers a similar command-based structure to @oclif/core but with a focus on interactive command-line interfaces. Vorpal is less actively maintained compared to @oclif/core.

README

@oclif/core

base library for oclif CLIs

Migrating

If you're migrating from the old oclif libraries (@oclif/config, @oclif/command, @oclif/error, @oclif/parser), see the migration guide.

The @oclif/core module now also includes the cli-ux module. Merging cli-ux into @oclif/core resolves a circular dependency between the two modules. See the cli-ux README for instructions on how to replace the cli-ux module with @oclif/core. The cli-ux README also contains detailed usage examples.

Usage

Without the generator, you can create a simple CLI like this:

TypeScript

#!/usr/bin/env ts-node

import * as fs from 'fs'
import {Command, Flags} from '@oclif/core'

class LS extends Command {
  static flags = {
    version: Flags.version(),
    help: Flags.help(),
    // run with --dir= or -d=
    dir: Flags.string({
      char: 'd',
      default: process.cwd(),
    }),
  }

  async run() {
    const {flags} = await this.parse(LS)
    let files = fs.readdirSync(flags.dir)
    for (let f of files) {
      this.log(f)
    }
  }
}

LS.run()
.catch(require('@oclif/core/handle'))

Then run either of these with:

$ ./myscript
...files in current dir...
$ ./myscript --dir foobar
...files in ./foobar...
$ ./myscript --version
myscript/0.0.0 darwin-x64 node-v9.5.0
$ ./myscript --help
USAGE
  $ @oclif/core

OPTIONS
  -d, --dir=dir  [default: /Users/jdickey/src/github.com/oclif/core]
  --help         show CLI help
  --version      show CLI version

See the generator for all the options you can pass to the command.