CLI App Builder

# CLI App Builder > Build CLI applications with Commander.js You are a Node.js CLI developer. The user wants to build command-line applications using Commander.js with subcommands, options, arguments, and help text. ## What to check first - Run `npm list commander` to verify Commander.js is installed (or `npm install commander`) - Check your Node.js version with `node --version` (Commander.js 11+ requires Node 16+) - Verify the entry point in `package.json` has a `bin` field pointing to your CLI file ## Steps 1. Create a new file (e.g., `cli.js`) and import Commander with `const { Command } = require('commander')` 2. Create a root program instance with `const program = new Command()` and set `.name()`, `.description()`, and `.version()` 3. Define global options using `.option()` before subcommands — e.g., `.option('-v, --verbose', 'verbose output')` 4. Add subcommands with `.command('name')` chained with `.description()`, `.argument()`, and `.action(callback)` 5. Inside the action callback, access arguments from the first parameter and options from the second parameter (the command object) 6. Use `.argument('<name>')` for required arguments and `.argument('[name]')` for optional ones 7. Add `.option()` to individual commands for command-specific flags like `--output` or `--force` 8. Call `.parse(process.argv)` at the end to trigger argument parsing and execute the matched command ## Code ```javascript const { Command } = require('commander'); const fs = require('fs'); const path = require('path'); const program = new Command(); program .name('mytool') .description('A sample CLI application built with Commander.js') .version('1.0.0'); program .option('-d, --debug', 'enable debug mode') .option('-c, --config <path>', 'path to config file'); program .command('create <project-name>') .description('Create a new project') .option('-t, --template <type>', 'project template', 'basic') .action((projectName, options, command) => { const globalOptions = command.parent.opts(); console.log(`Creating project: ${projectName}`); console.log(`Template: ${options.template}`); if (globalOptions.debug) console.log('Debug mode enabled'); const projectDir = path.join(process.cwd(), projectName); if (!fs.existsSync(projectDir)) { fs.mkdirSync(projectDir, { recursive: true }); console.log(`✓ Project directory created at ${projectDir}`); } }); program .command('build [entry]') .description('Build the project') .option('-o, --output <dir>', 'output directory', 'dist') .option('--minify', ' ``` *Note: this example was truncated in the source. See [the GitHub repo](https://github.com/Samarth0211/claude-skills-hub) for the latest full version.* ## Common Pitfalls - Treating this skill as a one-shot solution — most workflows need iteration and verification - Skipping the verification steps — you don't know it worked until you measure - Applying this skill without understanding the underlying problem — read the related docs first ## When NOT to Use This Skill - When a simpler manual approach would take less than 10 minutes - On critical production systems without testing in staging first - When you don't have permission or authorization to make these changes ## How to Verify It Worked - Run the verification steps documented above - Compare the output against your expected baseline - Check logs for any warnings or errors — silent failures are the worst kind ## Production Considerations - Test in staging before deploying to production - Have a rollback plan — every change should be reversible - Monitor the affected systems for at least 24 hours after the change --- *From [CLSkills.in](https://clskills.in/browse) — 2,300+ free Claude Code skills*