DNS switcher for macOS

myfi.rb

#!/usr/bin/env ruby

require 'optparse'
require 'pathname'
require 'yaml'

VERSION = '0.0.1'
HOMEDIR = Pathname.new(ENV['HOME'])

options = {
  config: HOMEDIR.join('.myfi.yml'),
  target: 'Wi-Fi', # Check your default service name by `networksetup -listallnetworkservices`
}

optparser = OptionParser.new do |opts|
  opts.banner = 'Usage: myfi [options]'
  opts.version = VERSION

  opts.on('-c CONFIG', '--c CONFIG', 'config file path') do |config|
    options[:config] = Pathname.new(config)
  end

  opts.on('-t TARGET', '--target TARGET', 'Target Network service') do |target|
    options[:target] = target
  end

  opts.on('-a DNS', '--add DNS', 'Add [DNS] set') do |dns|
    options[:cmd] = :add
    options[:dns] = dns
  end

  opts.on('-u DNS', '--use DNS', 'Use [DNS] set') do |dns|
    options[:cmd] = :set
    options[:dns] = dns
  end

  opts.on('-d', '--default', 'Use default DNS') do |dns|
    options[:cmd] = :set
    options[:dns] = 'default'
  end

  opts.on('-l', '--list', 'List DNS group') do |v|
    options[:cmd] = :list
  end

  opts.on('-n', '--now', 'Show current DNS group') do |v|
    options[:cmd] = :now
  end

  opts.on('-v', '--version', 'Show version') do |v|
    puts VERSION
    exit
  end
end

begin
  optparser.parse!
rescue OptionParser::ParseError => e
  $stderr.puts e.message
  exit 1
end

dns_group = {}
dns_group = YAML.load(options[:config].read) if options[:config].exist?

case options[:cmd]
when :add
  dns_group[options[:dns]] = ARGV.sort.uniq
  options[:config].write YAML.dump(dns_group)
when :set
  dns_records = dns_group[options[:dns]] || ['Empty']
  system('networksetup', '-setdnsservers', options[:target], *dns_records)
when :list
  dns_group.each_pair do |name, records|
    puts "* #{name}"
    records.each do |record|
      puts "  - #{record}"
    end
    puts
  end
when :now
  records = `networksetup -getdnsservers "#{options[:target]}"`.strip.split("\n").sort
  dns_group.each_pair do |name, rrecords|
    if rrecords.uniq.sort == records
      puts "* #{name}"
      exit 0
    end
    puts "* default"
  end
else
  $stderr.puts optparser.help
  exit 1
end