Ruby Daemons Gem

Question

I installed the ruby gem Daemons. To make sure it was working I created a script that would print to a file every 5 seconds. I then created another file to run the script using the trivial example they give you in the readme located at http://daemons.rubyforge.org/ . I require both rubygems and daemons. Then I type 'ruby mycontrol.rb start'. The example they use has some type of message saying '(myserver.rb is now running in the background)', I don't see that, but I don't get any errors. If I do a 'ps -u myusername' I see that the filed to be daemonized is listed in the processes, but doesn't appear to be running as nothing is getting written to the file.

Here is my source:

# this is mycontrol.rb

require 'rubygems'
require 'daemons'

Daemons.run(daemon.rb)

and...

# this is daemon.rb

loop do 
 open('file.out', 'w') do |f|
  f.puts 'hello everybody'
 end
 sleep(3)
end

Does anything I'm doing jump out at you as being wrong?

Thanks, Tony

Answer 1

I've tried your example and it works for me (Ruby 1.8.6 on Linux with Daemons version 1.0.10). However, you may be encountering the following issues:

• I found that the daemonized process (daemon.rb) was being started with a current working directory of /. This was not the current directory when running mycontrol.rb or the directory that contained daemon.rb. Running as a non-root user meant that my process didn't have permission to write the file. I changed the filename to /tmp/file.out and the file was created with the expected content.

• You are opening file.out in write-only ('w') mode. This means that it will be truncated and rewritten every 3 seconds. If you open the file in append ('a') mode you will see an additional hello everybody line written to the file every 3 seconds.

I don't see the 'is now running in the background' messages either. I assume this is included in the documentation to illustrate what should have happened rather than to indicate the output.