Simple hosts file parser

README.md

Simple hosts file parser

HostsParser.new(os: :mac).parse

Result:

{"127.0.0.1"=>
  ["localhost",
   "kubernetes.docker.internal"],
 "255.255.255.255"=>["broadcasthost"],
 "::1"=>["localhost"]}

hosts_parser.rb

class UnknowOSError < StandardError
  def initialize msg
    super(msg)
  end
end

class HostsParser
  OPERATING_SYSTEMS = %i(mac linux win)

  def initialize os:, keep_comment: false
    @os = os.downcase.to_sym
    raise ::UnknowOSError.new "Unknow OS #{@os}. OS list are: #{OPERATING_SYSTEMS}" unless
      OPERATING_SYSTEMS.include?(@os)

    @keep_comment = keep_comment
  end

  def parse
    hosts_content_by_os
  end

  private
  attr_reader :os, :keep_comment

  def hosts_content_by_os raw_content: false
    hosts_file_path = case os
                      when :mac, :linux
                        "/etc/hosts"
                      when :win
                        "C:\\Windows\\System32\\etc\\drivers\\hosts"
                      end
    hosts_content = ::File.read(hosts_file_path)

    return hosts_content if raw_content

    hosts_content.split("\n").each_with_object({}) do |line, obj|
      line = line.strip

      if (line.present? && line !~ /^\#/ && line != "\n")
        line = line.split(/\s+/)
        hosts_ip = line.shift

        (obj[hosts_ip] ||= []).concat(line)
      end
    end
  end
end