bin.js

#!/usr/bin/env node
require('yargs')
  .scriptName('cat')
  .command(
    '$0 [FILE..]',
    'Concatenate FILE(s) to standard output.',
    function (yargs) {
      return yargs
        .positional('FILE', {
          describe: 'input file',
          defaultDescription: 'standard input'
        })
    },
    function (args) {
      if (args.FILE) {
        require('run-series')(
          args.FILE.map(function (file) {
            return function (done) {
              require('fs').createReadStream(file)
                .once('end', function () {
                  done()
                })
                .pipe(process.stdout)
            }
          })
        )
      } else {
        process.stdin.pipe(process.stdout)
      }
    }
  )
  .help()
  .alias('h', 'help')
  .parse()