Module: Daemonize

Included in:
PatternPark::FCSHD
Defined in:
lib/airake/daemonize.rb

Overview

Daemonize code provided by Travis Whitton

grub.ath.cx/daemonize/

Instance Method Summary collapse

Instance Method Details

#daemonize(oldmode = 0, closefd = false) ⇒ Object

This method causes the current running process to become a daemon

If closefd is true, all existing file descriptors are closed



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# File 'lib/airake/daemonize.rb', line 28

def daemonize(oldmode=0, closefd=false)
  srand # Split rand streams between spawning and daemonized process
  safefork and exit # Fork and exit from the parent

  # Detach from the controlling terminal
  unless sess_id = Process.setsid
    raise 'Cannot detach from controlled terminal'
  end

  # Prevent the possibility of acquiring a controlling terminal
  if oldmode.zero?
    trap 'SIGHUP', 'IGNORE'
    exit if pid = safefork
  end

  Dir.chdir "/"   # Release old working directory
  File.umask 0000 # Insure sensible umask

  if closefd
    # Make sure all file descriptors are closed
    ObjectSpace.each_object(IO) do |io|
      unless [STDIN, STDOUT, STDERR].include?(io)
        io.close rescue nil
      end
    end
  end

  STDIN.reopen "/dev/null"       # Free file descriptors and
  STDOUT.reopen "/dev/null", "a" # point them somewhere sensible
  STDERR.reopen STDOUT           # STDOUT/STDERR should go to a logfile
  return oldmode ? sess_id : 0   # Return value is mostly irrelevant
end

#safefork ⇒ Object

Try to fork if at all possible retrying every 5 sec if the maximum process limit for the system has been reached



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# File 'lib/airake/daemonize.rb', line 9

def safefork
  tryagain = true

  while tryagain
    tryagain = false
    begin
      if pid = fork
        return pid
      end
    rescue Errno::EWOULDBLOCK
      sleep 5
      tryagain = true
    end
  end
end