Sample script demonstrating that when starting two listeners, only the second listener responds to file system events

gistfile1.rb

# Using Ruby 2.0.0p195 and listen 2.3.0

require 'listen'
require 'fileutils'

dir1 = '/Users/blue39/tmp/dir1'
FileUtils.remove_dir(dir1, true)
FileUtils.mkdir_p(dir1)

dir2 = '/Users/blue39/tmp/dir2'
FileUtils.remove_dir(dir2, true)
FileUtils.mkdir_p(dir2)

listener1 = Listen.to(dir1) do | modified, added, removed |
  puts "listener1: modified: #{modified.inspect}, added: #{added.inspect}, removed: #{removed.inspect}"
end

listener2 = Listen.to(dir2) do | modified, added, removed |
  puts "listener2: modified: #{modified.inspect}, added: #{added.inspect}, removed: #{removed.inspect}"
end

listener1.start
listener2.start

# Add a file to dir1
file_path = "#{dir1}/test.txt"
file = File.open(file_path, "w")
file.write("Testing")
file.close
sleep 1   # give listener1 time to respond to this file event

# Add a file to dir2
file_path = "#{dir1}/test.txt"
file = File.open(file_path, "w")
file.write("Testing")
file.close
sleep 1   # give listener2 time to respond to this file event

begin
  listener1.stop
rescue SystemExit
  puts "listener1: Eat #{$!.class} exception"
end
begin
  listener2.stop
rescue SystemExit
  puts "listener2: Eat #{$!.class} exception"
end

puts "Done!"

# The following appears in the console.  Warning is triggered by stopping the second listner (line 17).
#
# listener2: modified: [], added: ["/Users/blue39/tmp/dir1/test.txt"], removed: []
# listener2: modified: ["/Users/blue39/tmp/dir1/test.txt"], added: [], removed: []
# listener1: Eat SystemExit exception
# [Listen warning]: Change block raised an exception: actor already terminated
# Backtrace:
#   /Users/blue39/.rvm/gems/ruby-2.0.0-p195@listen_test/gems/celluloid-0.15.2/lib/celluloid/proxies/actor_proxy.rb:66:in `terminate!'
#   /Users/blue39/.rvm/gems/ruby-2.0.0-p195@listen_test/gems/celluloid-0.15.2/lib/celluloid/proxies/actor_proxy.rb:59:in `terminate'
#   /Users/blue39/.rvm/gems/ruby-2.0.0-p195@listen_test/gems/listen-2.2.0/lib/listen/listener.rb:158:in `_terminate_actors'
#   /Users/blue39/.rvm/gems/ruby-2.0.0-p195@listen_test/gems/listen-2.2.0/lib/listen/listener.rb:141:in `_wait_for_changes'
#   /Users/blue39/.rvm/gems/ruby-2.0.0-p195@listen_test/gems/listen-2.2.0/lib/listen/listener.rb:40:in `block in start'
# Done!