#!ruby -Ks

class Which
  OPT_ALL = "-A"

  # コンストラクタ
  def initialize(param)
    @option   = nil
    @filename = nil
    @path     = nil

    if param.is_a?(Array)
      @option   = param.include?(OPT_ALL)
      @filename = get_filename(param)
      @path     = ENV['PATH']
    end
  end

  # 探すファイル名を取り出す
  def get_filename(param)
    param.each do |x|
      return x if x != OPT_ALL
    end
    return nil
  end
  private :get_filename

  # ファイルを探して標準出力する
  def search()
    if @filename == nil
      print "Usage: which <command_name> [-a]\n"
    else
      result = search_command()
      if result == ""
        print "command " + @filename + " not found.\n"
      else
        print result
      end
    end
  end

  # ファイルを探す本当の処理
  def search_command()
    count = 0
    result = ""
    @path.split(";").each do |path|
      path = path.gsub(/\A\"|\"\Z/,"")
      if FileTest.directory?(path)
        Dir.foreach(path) do |file|
          if FileTest.file?(path + "\\" + file) &&
            file.match(/\A#{@filename}\./i)
            result += path + "\\" + file + "\n"
            count += 1
            if !@option
              return result
            end
          end
        end
      end
    end
    return result
  end
  private :search_command
end

a = Which.new(ARGV.map{|x| x.upcase})
a.search