gistfile1.txt

require 'readline'

# Empty and dup are BAD.
#   1. Read line and append to history
#   2. Quick Break on nil
#   3. Remove from history if empty or dup

def readline_lineread
  line = Readline.readline('> ', true)
  return nil if line.nil?
  if line =~ /^\s*$/ or Readline::HISTORY.to_a[-2] == line
    Readline::HISTORY.pop
  end
  line
end

# Debug
while line = readline_lineread
  p line
  p Readline::HISTORY.to_a
end