require "ftools"
def changeLink(emacs,dir="/usr/bin/")
  Dir.open(dir).each{ |name|
    fullpath = dir+name
    if fullpath =~/\.#{emacs}$/
    then
      srcname = fullpath
      distname = fullpath.dup
      distname.sub!(/\.#{emacs}$/,"")
      File.unlink(distname) if File.symlink?(distname)
      File.symlink(srcname,distname)
    end

  }

end
changeLink("emacs-21.0.104",Dir.pwd+"/")