Simple script for updating the /etc/hosts file

update-hosts.js

#!/usr/bin/env node

/** @author Adrian Moreno (https://github.com/adriem) */

const https = require('https')
const fs = require('fs')

const urls = process.argv.slice(2).filter(arg => arg !== '-v' && arg !== '--verbose')
const verbose = process.argv.includes('-v') || process.argv.includes('--verbose')

const defaultUrls = [
  // PUT YOUR DEFAULT URLS HERE
]

async function fetchIp(url) {
  const dnsData = await new Promise((resolve, reject) => {
    let rData = ''
    https
      .get(`https://dns.google.com/resolve?name=${url}`, (response) => {
        response.on('data', (chunk) => rData += chunk)
        response.on('end', () => resolve(JSON.parse(rData)['Answer']))
      })
      .on('error', reject)
  })

  return dnsData.find((it) => it.type == 1).data
}

async function updateHostsFile(urls) {
  let hostsFileContent = fs.readFileSync('/etc/hosts', 'utf8')

  await Promise.all(urls.map(async url => {
    const entryRegex = new RegExp(`[\\.\\d]*[ \\t]+${url}`, 'ig')
    const newHostEntry = `${await fetchIp(url)}\t${url}`

    const isExistingEntry = entryRegex.test(hostsFileContent)

    hostsFileContent = isExistingEntry
      ? hostsFileContent.replace(entryRegex, newHostEntry)
      : `${hostsFileContent}${newHostEntry}\n`

    if (verbose) console.log(`ENTRY UPDATED: ${newHostEntry}`)
  }))

  fs.writeFileSync('/etc/hosts', hostsFileContent, 'utf8')
}

updateHostsFile(urls.length > 0 ? urls : defaultUrls)