Commander.js CLI Framework

Quick Start

import { Command } from 'commander';

const program = new Command();

program
  .name('mycli')
  .version('1.0.0')
  .description('My CLI tool');

program
  .command('build <input>')
  .description('Build the project')
  .option('-o, --output <file>', 'Output file', 'output.json')
  .option('-w, --watch', 'Watch mode')
  .option('-v, --verbose', 'Verbose output')
  .action((input, options) => {
    console.log(`Building ${input} to ${options.output}`);
    if (options.watch) startWatcher();
  });

program.parse();

Command Patterns

| Pattern | Syntax | Description | |---------|--------|-------------| | Required arg | <name> | Must be provided | | Optional arg | [name] | Can be omitted | | Variadic | <files...> | Multiple values | | Option value | -o, --out <file> | Option with value | | Boolean flag | -v, --verbose | True when present | | Negatable | --no-cache | Sets cache=false |

Subcommands

const build = program.command('build');

build
  .command('dev')
  .description('Development build')
  .action(() => { /* ... */ });

build
  .command('prod')
  .description('Production build')
  .action(() => { /* ... */ });

Key Features

// Default values
.option('-p, --port <number>', 'Port', '3000')

// Coercion
.option('-n, --number <n>', 'A number', parseInt)

// Required options
.requiredOption('-c, --config <path>', 'Config file')

// Choices
.option('-e, --env <env>', 'Environment').choices(['dev', 'prod'])

// Error handling
program.exitOverride(); // Throw instead of process.exit
program.configureOutput({ writeErr: (str) => logger.error(str) });

Tips

• Use program.parse() at the end, or program.parseAsync() for async
• Access args via action callback or program.args
• Use .alias('b') for command shortcuts
• Add examples with .addHelpText('after', 'Examples:\n $ mycli build src/')