gistfile1.rb

#define a recursive function that will traverse the directory tree
def printAndDescend(pattern)
  #we keep track of the directories, to be used in the second, recursive part of this function
  directories=[]
  Dir['*'].sort.each do |name|
    if File.file?(name) and name[pattern]
      puts(File.expand_path(name))
    elsif File.directory?(name)
      directories << name
    end
  end
  directories.each do |name|
    #don't descend into . or .. on linux
    Dir.chdir(name){printAndDescend(pattern)} if !Dir.pwd[File.expand_path(name)]
  end
end
#print all ruby files
printAndDescend(/.+\.rb$/)