Making Command-line interface (CLI) for fun and profit

Next time you have an idea 💡 "I know... Why don't I write a script to automate this thing?" Actually, you should not, you should write a CLI instead.

CLI has better structure than scripts. CLI uses flags and help text to avoid mistakes. For example:

$ moa --help
Moa makes it easier to run your local node.js apps.

USAGE
  $ moa

OPTIONS
  -c, --commands=commands  [default: start] commands to run.
  -h, --help               show CLI help
  -r, --root=root          [default: ../] root path to run.

DESCRIPTION
  ...
  Have some fun

Scripts are messy. And can get out of control.

At Taggun, we run a lot of node.js application. We make APIs for receipt OCR scanning, by the way. So, I recommend oclif: The Open CLI Framework by Heroku.

How to create a new CLI

Install node.js first.

Start by scaffolding

$ npx oclif single moa
? npm package name (moa): moa
$ cd moa

Modify your flags in src\index.js

MoaCommand.flags = {
  // add --help flag to show CLI version
  help: flags.help({char: 'h'}),
  commands: flags.string({char: 'c', description: 'commands to run. Comma-separated.', default: 'start'}),
  root: flags.string({char: 'r', description: 'root path to run.', default: '../'}),
}

Modify your description in src\index.js

MoaCommand.description = `Moa makes it easier to run your local node.js apps.

Modify your command in src\index.js

class MoaCommand extends Command {
  async run() {
    const {flags} = this.parse(MoaCommand)
    const commands = flags.commands.split(',')
    const {root} = flags
    find.file(/(?<!node_modules\/.*)\/package\.json$/, root, files => {
      files.forEach(async file => {
        const cwd = require('path').dirname(file)
        commands.forEach(async command => {
          this.log(cwd, `npm run ${command}`)
          const npm = spawn('npm', ['run', command], {cwd})
          for await (const output of npm.stdout) {
            this.log(`${file}: ${output}`)
          }
        })
      })
    })
  }
}

In this example, you will need to run npm i find to install find npm module.

This simple CLI will look for all node.js application in the [root] and run npm run [command]. Great if you need to run multiple node.js application to start coding.

Run it

./bin/run -c start -c ../taggun/

Publish and share your CLI

See https://oclif.io/docs/releasing