From: Tim Pease <tim.pease@...>
Date: 2009-04-25T00:11:16+09:00
Subject: proper way to daemonize

module Process
  def self.daemon( nochdir = nil, noclose = nil )
    exit if fork                    # Parent exits, child continues.
    Process.setsid                   # Become session leader.
    exit if fork                    # Zap session leader.

    unless nochdir
      Dir.chdir "/"                  # Release old working directory.
    end

    File.umask 0000                  # Ensure sensible umask. Adjust as needed.

    unless noclose
      STDIN.reopen "/dev/null"       # Free file descriptors and
      STDOUT.reopen "/dev/null", "a" # point them somewhere sensible.
      STDERR.reopen '/dev/null', 'a'
    end

    return 0
  end
end


This is the standard code to daemonize a process. The use of "exit"
bothers me slightly, as it will call all "at_exit" handlers in the
parent. I do not believe this is the desired behavior; the "at_exit"
handlers will free resources that the daemonized process might need.
Instead, "exit!" should be used to prevent "at_exit" handlers from
being called.

Any thoughts about this subtle change? Are there any undesirable side
effects that arise from using exit! instead of exit ?

Blessings,
TwP