ini.rb

class ConfigParseError < StandardError
  def initialize(file_name,line,text)
    @file_name,@line,@text = file_name,line,text
    super("Error in config file #{@file_name} at line #{line}. Line content \"#{@text}\" is incorrect.")
  end
end

class ConfigReader
  LINE_CONTINUE = /\\\s*$/
  def self.read_config(file_name)
    result = {}
    prepend = ""
    section = "default"
    result[section] = {}
    File.open(file_name, "r") do |io|
      line_number = 0
      (io.readlines + [""]).each do |line|
        line_number += 1
        line.chomp!
        unless prepend.empty?
          line = prepend + line.strip
        end
        prepend = ""
        case line
        when LINE_CONTINUE
          prepend = line.sub(LINE_CONTINUE,"")
          next
        when ""
          next
        end
        if it=try_as_section_name(line)
          section = it
          result[section] ||= {}
          next
        end
        match_data = line.match(/([^=]+)=\s*(.*)/)
        if match_data
          key, value = match_data[1].strip, match_data[2].strip
          result[section][key] = value
        else
          throw ConfigParseError.new(file_name,line_number,line)
        end
      end
    end
    result
  end

  private

  def self.try_as_section_name(line)
    match = line.match(/^\s*\[\s*([^\[\]]+)\s*\]\s*$/)
    match && match[1]
  end

end

p ConfigReader.read_config(ARGV[0] || "test.ini")