Handling Input and Output of a Daemon

Question

I want to create a daemon of a ruby program on Linux.

I also want the daemon to be interactive-I want to be able to send input to the daemon through a file/pipe/the simplest method and receive output to a file.

How do I go about doing this?

I've looked into the module daemons (http://daemons.rubyforge.org/), threads and the method popen3 but I'm having a hard time getting them to do the above.

ANSWER: Mladen's method:

I have the controller that creates the daemon: (you'll need the daemons module gem)

require 'rubygems'
require 'daemons'

Daemons.run('/myDaemon.rb', {:app_name => "o", :dir_mode => :normal, :dir => '', :log_output => true, :multiple => true })

Here's myDaemon.rb:

puts `pwd`

File.open('my_pipe', 'r+') do |f|
    loop do
            line = f.gets
            puts "Got: #{line}"
    end
end

Steps: Both files are in my root directory \. The Daemons.run creates the daemon in \.

1. Create a named pipe, mkfifo ./my_pipe.

2. ruby controller.rb start

3. cat > my_pipe

4. type text

5. ctrl-c to stop input

6. cat o.output to see your output

Answer 1

Probably the simplest way, named pipes, based on http://www.pauldix.net/2009/07/using-named-pipes-in-ruby-for-interprocess-communication.html:

Step 1: Create a named pipe

mkfifo ./my_pipe

Step 2: Create your "daemon":

File.open('my_pipe', 'r+') do |f|
  loop do
    line = f.gets
    puts "Got: #{line}"
  end
end

and run it.

Step 3: Open another terminal and run

cat > my_pipe

and start typing some text, line by line.

Step 4: Watch output of the daemon.

Step 5: ???

Step 6: Profit.