CLI App Builder

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

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 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