Daemons lib not dong much?

Hello - I’m trying to run a background daemon that will monitor changes
in a mysql database. The file to monitor the changes works fine when run
by itself from the prompt as
$ ruby changes.rb

However, when I try to use it in a daemon file, not much happens. Here’s
the file (changes_daemon.rb):

require ‘daemons’

all the other required come here

def main

if FILE == $0

When I run this at the prompt:
$ruby changes_daemon.rb start
$ (next shell line after hitting return - no errors)

Nothing happens (it’s supposed to write to a table and a log file, so I
can see if anything occurs).

Any insights will be great - thanks!