[Tools] Create a Simple CLI Tool in Node.js with CAC

Command-line tools can help you with all sorts of tasks. This lesson covers the very basics of setting up a CLI tool in Node.js by creating your project with npm, setting up your bin script, and using CAC to parse a single argument.

Create a new project, change the "name" porp's value to "hi", then add a "bin" prop, so next time, when we invoke "hi", it will run the command in "bin".

package.json

{
  "name": "hi",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo "Error: no test specified" && exit 1"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "bin": "./index.js",
  "devDependencies": {
    "cac": "6.3.12"
  }
}

Install:

npm i -D cac

Create index.js file:

• Make sure you have '

  #!/usr/bin/env node

  ' on the top of the file, then it knows should run in node env.
• Using cac to build commad, you can define 'option', 'command'
• Last you should always call cli.parse() to run the command

#!/usr/bin/env node

const cli = require('cac')();
cli.option('--type <type>', 'Provide type, [date|foo]')
// name is a required field
cli.command('<name>', 'Provide your name')
    .action((name, options) => {
        const {type} = options;
        if (type === 'date') {
            console.log(`Hi ${name}, Today is ${new Date().toDateString()}`)
        } else if (type === 'foo') {
            console.log(`Hi ${name}, you should take a rest!`)
        } else {
            console.log(`Hi ${name}, Good job!`)
        }
        
    })

cli.help()
// Display version number when `-h` or `--help` appears
cli.version('0.0.0')
cli.parse()

Run: