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demon.rb - the ruby daemon library you've been waiting for

a small, flexible, powerful ruby daemon library

demon.rb aims to make it simple to construct extremely well behaved daemon programs in no time.

it supports both a DSL and object oriented interface to sound unix daemon code. unlike some daemon libraries, it makes zero assumptions about how you want to organize your code - although some sane defaults exist to help you along if you don't what to think about this at all.

gem 'demon'

simple usage is simple...

#! /usr/bin/env ruby

# file: a.rb

Demon do
  loop do
    stuff_as_a_daemon
  end
end

  ./a.rb help 

---
start: start in daemon mode
run: run in the foreground, but otherwise like a daemon
stop: stop any currently running daemon
restart: restart any currently running daemon, or start a new one
pid: print the pid of the running daemon, iff any
ping: ensure a daemon is running, start one iff not
signal: hit the daemon, if any, with SIGUSR2
tail: tail -F all auxillary files (lock files, logs, etc)
fuser: report the fuser of any auxillary files (lock files, logs, etc)
log: display the location of the log file
root: display the location of the root daemon dir (lock files, logs, etc)
modes: print all modes, even those without "help"
help: this message

a few things to notice about the above daemon:

• daemons are expected to run for a long time. demon.rb will run the supplied block over and over (aka. it is an implied loop)
• if the supplied block blows up the error will be logged, and the block retried. we assume you mean to keep your daemon up.
• the actual script being run must be know to demon.rb. you can let it know by passing a block, or supplying the location of the script as the first arugment

Demon __FILE__ do
  # stuff
end

of course, you can have much more find grained control over your daemons

  class MyProgram 
    def run
      loop do
        teh_awesome
      end
    end

    def daemonize!
      program = self

      demon.start{ program.run }
    end

    def pid 
      demon.run(:pid)
    end

    def demon
      @demon ||= Demon.new(__FILE__, :root => '~/.my_progarm/')
    end
  end