Ruby script that checks the PATH environment variable, and displays its directories one per line

check_path.rb

#!/usr/bin/ruby

abort 'PATH is not set' if ENV['PATH'].nil?

seen = Hash.new
output = ''

ENV['PATH'].split(':').each do |p|
  seen[p] = seen[p].nil? ? 1 : seen[p]+1
  output += " #{p}"
  output += '  # does NOT exist' unless File.directory?(p)
  output += '  # duplicate' if seen[p] > 1
  output += '  # current directory (.) in PATH is discouraged' if p == '.'
  output += "\n"
end

puts "\n#{output}\n"