--- Dir.chdir([path])
--- Dir.chdir([path]) {|path| ... }  ruby 1.7 feature

    ȥǥ쥯ȥ path ѹޤ
    path ά硢Ķѿ HOME ޤ LOGDIR 
    ꤵƤФΥǥ쥯ȥ˰ưޤ

    ȥǥ쥯ȥѹ 0 ֤ޤԤ
    㳰 Errno::EXXX ȯޤ

    ruby 1.7 feature:
    ֥åꤵ줿硢ǥ쥯ȥѹϥ֥åμ¹˸
    ޤϰʲǤ

        savedir = Dir.pwd
        Dir.chdir(newdir)
        begin
          ...
        ensure
          Dir.chdir(savedir)
        end

    ֥åꤵ줿ȤΤΥ᥽åɤͤϥ֥åμ¹Է
    Ǥ

