daemon_control

#!/usr/bin/env ruby
######################################################
###
##  File: daemon_control
##  Desc: daemon control element of the im_gateway.rb server
#
# NOTE: Supports the following command line arguments:
#       start stop restart status
#
# NOTE: The pid file is parent directory of the server as:
#       #{server.basename}.pid

require 'pathname'
require 'daemons'

me = Pathname.new __FILE__

usage = <<~USAGE

  Usage:  #{me.basename} rb_program [start | stop | restart | status]

  Where:
    rb_program is a path to a Ruby program.

  Options:
    start         start an instance of the rb_program
    stop          stop all instances of the rb_program
    restart       stop all instances and restart them afterwards
    reload        send a SIGHUP to all instances of the rb_program
    run           start the rb_program and stay on top
    zap           set the rb_program to a stopped state
    status        show status (PID) of rb_program instances

  NOTE:

    A pid (process ID) file is used in the same directory as
    the rb_program.  It has the same base name with the extension
    of '.pid'

USAGE


if  ARGV.empty?               ||
    ARGV.include?('--help')   ||
    ARGV.include?('-h')       ||
    %w[start stop restart status].include?(ARGV[0].downcase)
  puts usage
  exit
end

rb_program = Pathname.new(ARGV.shift)

unless rb_program.exist?
  puts <<~ERROR

    Error: Program does not exist.  #{rb_program}

  ERROR
  puts usage
  exit(-1)
end

Daemons.run(rb_program.realpath)