hilong -- A simply utility to show character counts for each line of input and highlight lines longer than 80 characters.

gistfile1.rb

#!/usr/bin/env ruby

# A simply utility to show character counts for each line of input and
# highlight lines longer than 80 characters.
#
# Written as an example for {post}
#
# Examples:
#
# $ hilong Gemfile
# $ hilong Gemfile | more
# $ hilong Gemfile > output.txt
# $ hilong Gemfile Gemfile.lock
# $ cat Gemfile* | hilong
# $ cat Gemfile | hilong - Gemfile.lock

# escaped bash color codes
red = "\e[31m"
reset_color = "\e[0m"

maximum_line_length = 80

# Keep reading lines of input as long as they're coming.
ARGF.each_line do |line|
  # Construct a string that begins with the length of this line
  # and ends with the content. The trailing newline is #chop'ped 
  # off of the content so we can control where the newline occurs.
  # The string are joined with a tab character so that indentation
  # is preserved.
  output_line = [line.size, line.chop].join("\t")

  # If the line is long and our $stdout is not being piped then we'll
  # colorize this line.
  if $stdout.tty? && line.size > maximum_line_length
    # Turn the output to red starting at the first character.
    output_line.insert(0, red)
    # Reset the text color back to what it was at the end of the
    # line.
    output_line.insert(-1, reset_color)
  end

  $stdout.puts output_line
end

Great example of using pipes with ruby io :)