gistfile1.rb

module Truncate
  # only add ellipsis on a word boundary, do not break a word
  def truncate(char_num)
    # return a new string
    self.gsub(/((?:.|\n){#{char_num}}[\w.]*)((?:.|\n)*)/) {$2.empty? ? $1 : $1 + '...'}
  end
end

class String
  include Truncate
end


"hello world".truncate(3) #=> "hello..."