Show the manpage of a random executable in your $PATH

cotd.rb

#!/usr/bin/env ruby
# Command of the day
# Picks a random executable from your path until it finds one with a manpage.
# Use this to learn about some of the really obscure yet really useful scripts that are already on your system.

files = ENV["PATH"].split(":").uniq.compact.map { |path|
  Dir.glob(File.join(path,'*')).select {|file| File.file?(file) && File.executable?(file)}
}.flatten.compact.uniq

cotd = File.basename(files[rand(files.size)])
until system "man #{cotd} > /dev/null 2>&1"
  cotd = File.basename(files[rand(files.size)])
end
puts "Command of the day is: #{cotd}"
exec "man #{cotd}"