CLI Tool Development

CLI Tool Development

Project Structure

src/
  index.ts          # Entry point with shebang
  cli.ts            # Commander setup
  commands/         # Command handlers
  ui/               # Ink components (if interactive)
  utils/            # Helpers
  types.ts          # Type definitions

Commander.js Setup

#!/usr/bin/env node
import { Command } from 'commander';
import packageJson from '../package.json' with { type: 'json' };

const program = new Command();

program
  .name('mytool')
  .description('My awesome CLI tool')
  .version(packageJson.version);

program
  .command('init')
  .description('Initialize a new project')
  .option('-t, --template <name>', 'Template to use', 'default')
  .option('-f, --force', 'Overwrite existing files', false)
  .action(async (options) => {
    await initCommand(options);
  });

program.parseAsync();

User Feedback with Chalk & Ora

import chalk from 'chalk';
import ora from 'ora';

// Status messages
console.log(chalk.green('✓') + ' Operation complete');
console.log(chalk.red('✗') + ' Operation failed');
console.log(chalk.yellow('⚠') + ' Warning message');

// Progress spinner
const spinner = ora('Loading...').start();
try {
  await longOperation();
  spinner.succeed('Done!');
} catch (error) {
  spinner.fail('Failed');
}

Interactive Prompts with Enquirer

import enquirer from 'enquirer';

const { name } = await enquirer.prompt<{ name: string }>({
  type: 'input',
  name: 'name',
  message: 'Project name:',
  validate: (v) => v.length > 0 || 'Name required',
});

const { confirm } = await enquirer.prompt<{ confirm: boolean }>({
  type: 'confirm',
  name: 'confirm',
  message: 'Continue?',
  initial: true,
});

Ink for Rich TUI

import React, { useState } from 'react';
import { render, Box, Text, useInput } from 'ink';

function App() {
  const [selected, setSelected] = useState(0);
  const items = ['Option 1', 'Option 2', 'Option 3'];

  useInput((input, key) => {
    if (key.downArrow) setSelected(s => Math.min(s + 1, items.length - 1));
    if (key.upArrow) setSelected(s => Math.max(s - 1, 0));
    if (key.return) process.exit(0);
  });

  return (
    <Box flexDirection="column">
      {items.map((item, i) => (
        <Text key={i} color={i === selected ? 'cyan' : undefined}>
          {i === selected ? '>' : ' '} {item}
        </Text>
      ))}
    </Box>
  );
}

render(<App />);

Configuration Management

import fs from 'fs-extra';
import path from 'node:path';
import os from 'node:os';

const CONFIG_DIR = path.join(os.homedir(), '.mytool');
const CONFIG_FILE = path.join(CONFIG_DIR, 'config.json');

async function loadConfig(): Promise<Config> {
  await fs.ensureDir(CONFIG_DIR);
  if (await fs.pathExists(CONFIG_FILE)) {
    return fs.readJson(CONFIG_FILE);
  }
  return getDefaultConfig();
}

async function saveConfig(config: Config): Promise<void> {
  await fs.writeJson(CONFIG_FILE, config, { spaces: 2 });
}

Error Handling

// Graceful exit handling
process.on('SIGINT', () => {
  console.log('\nCancelled');
  process.exit(0);
});

// Top-level error handler
try {
  await program.parseAsync();
} catch (error) {
  console.error(chalk.red('Error:'), error.message);
  process.exit(1);
}

Package.json Setup

{
  "bin": {
    "mytool": "./dist/index.js"
  },
  "files": ["dist"],
  "type": "module",
  "scripts": {
    "build": "tsup src/index.ts --format esm --dts",
    "dev": "tsx src/index.ts"
  }
}

Best Practices

1. Add #!/usr/bin/env node shebang to entry file
2. Support both flags (-f) and options (--force)
3. Provide helpful error messages with suggestions
4. Support --help and --version flags
5. Use exit codes: 0 for success, 1 for error
6. Support piping and stdin when appropriate
7. Respect NO_COLOR environment variable