Watch File System Changes and Trigger Script http://midgetontoes.com/blog/2014/03/22/ruby-watch-file-system-changes-and-trigger-script/

file_watch_sample.rb

#!/usr/bin/env ruby

require 'optparse'
require 'fssm'
require 'rbconfig'

THIS_FILE = File.expand_path(__FILE__)
 
RUBY = File.join(RbConfig::CONFIG['bindir'], RbConfig::CONFIG['ruby_install_name'])

options = {}
 
optparse = OptionParser.new do|opts|
	opts.banner = "Usage: file_watch_sample.rb [options]"
 
	options[:watch_file] = nil
	opts.on('-f', '--file FILE', 'FILE to watch') do |file|
		options[:watch_file] = file
	end
 
	opts.on('-h', '--help', 'Display this screen') do
		puts opts
	 	exit
	end
end
 
optparse.parse!

raise OptionParser::MissingArgument if options[:watch_file].nil?

watch_file = options[:watch_file]

watch_dir = File.dirname(watch_file)
watch_filename = File.basename(watch_file)
process_script = File.join(File.dirname(THIS_FILE), 'test.rb')

FSSM.monitor(watch_dir, watch_filename) do
	update {|base, relative|
		puts "Watch file #{watch_file} changed"
		output = `#{RUBY} #{process_script}`
		puts output
	}
end