rename_files

# use => ruby rename.rb .jpg thumb_

def generate
  files = Dir.entries(".")
  
  count = 1
  files.each do |f|
    extension = f[/\.[a-z]+$/]
    if extension == ARGV[0]
      new_name = "#{ARGV[1]}#{count.to_s}#{extension}"
      File.rename(f, new_name)
      puts "rename #{f} to #{new_name}"
      count+=1
    end
  end
end