a filter to colorize output

highlight.rb

#!/usr/bin/ruby
# encoding: utf-8
#
# filter to colorize output
#
# cat file | highlight aaa bbb cc
#
#   aaa,bbb,ccc all get assigned different colors and are highlighted in the output
#

class String
  def mgsub(key_value_pairs=[].freeze)
    regexp_fragments = key_value_pairs.collect { |k,v| k }
    gsub( Regexp.union(*regexp_fragments)) do |match|
      key_value_pairs.detect{|k,v| k =~ match}[1] + $1 + "\x1b[0m"
    end
  end
end


class Highlight
  COLORS = %w[ 01 02 11 12 13 166 03 10 190 196 207 208 136 217 226 39 46 104 172 23 22 157 181 ]
  RESET_COLOR = "\x1b[0m"

  def initialize(terms)
    @colors = assign_colors(terms)
  end

  def stream(io_stream)
    while line = io_stream.gets
    #io_stream.each_line do |line|
      if line =~ /highlight:\s+(.*)$/
        @colors = assign_colors($1.to_s.split(/\s+/))
      end
      $stdout.puts line.mgsub(@colors)
    end
  end

  private

  def color(fg, bg)
    c = ""
    c += "\x1b[38;5;#{fg}m" if fg
    c += "\x1b[48;5;#{bg}m" if bg
    c
  end

  def assign_colors(terms)
    colors = []
    unless terms.nil? || terms.empty?
      if terms.size > COLORS.size
        $stderr.puts "More terms than colors, some colors will repeat"
      end
      terms.each_with_index do |term,i|
        attr = 1
        fg = COLORS[i % COLORS.size]
        bg = nil
        regex = Regexp.new("(%s)" % [term])
        colors << [regex, color(fg,bg)]
        #p "%s - %d - %s" % [term,i,colors[regex]]
      end
    end
    return colors
  end

end

STDOUT.sync = true
Highlight.new(ARGV).stream($stdin)