line_count_wrap.mjs

#!/usr/bin/env node
import yargs from 'yargs';
import fs from 'node:fs';

const argv = yargs(process.argv.slice(2))
  .usage('Count the lines in a file.\nUsage: $0')
  .wrap(80)
  .demand('f')
  .alias('f', ['file', 'filename'])
  .describe(
    'f',
    "Load a file. It's pretty important." +
      " Required even. So you'd better specify it."
  )
  .alias('b', 'base')
  .describe('b', 'Numeric base to display the number of lines in')
  .default('b', 10)
  .describe('x', 'Super-secret optional parameter which is secret')
  .default('x', '')
  .parse();
const s = fs.createReadStream(argv.file);

let lines = 0;
s.on('data', function (buf) {
  lines += buf.toString().match(/\n/g).length;
});

s.on('end', function () {
  console.log(lines.toString(argv.base));
});