Ruby: Minecraft process launcher

mc_server.rb

#!/usr/bin/env ruby

# Minecraft server launcher, by Benjamin Kreeger <ben@kree.gr>.
# Feel free to shamelessly steal this script. I don't care.
# I renamed mine to `mc_server` and did a `chmod +x` on it so I
# wouldn't have to type `ruby mc_server.rb` on it every time I
# wanted to launch my server in the background.
#
# Make sure this is in the same directory as your
# `minecraft_server.jar` file. I haven't tested it otherwise, and
# I'm sure it won't work.
#
# It expects you to have a Java runtime installed, and it expects
# your Minecraft server jar to be named `minecraft_server.jar`. If
# you've renamed it, feed `--jar new-jar-name.jar` to the script.
#
# For more help and options, run it with an `-h` or `--help` flag.
#
# Enjoy.

require 'logger'
require 'optparse'

PIDFILE = 'pidfile'

options = {}

OptionParser.new do |opts|
  opts.banner = 'Minecraft server launcher. Usage: mc_server.rb [options]'

  options[:stop] = false
  opts.on('-s', '--stop', 'Stop any running server.') do
    options[:stop] = true
  end

  options[:verbose] = false
  opts.on('-v', '--[no-]verbose', 'Run verbosely.') do
    options[:verbose] = true
  end

  options[:memory] = 1024
  opts.on('-m', '--memory AMOUNT', 'Allocate AMOUNT to server memory.') do |amount|
    options[:memory] = amount
  end

  options[:jar] = 'minecraft_server.jar'
  opts.on('-j', '--jar /PATH/TO/MINECRAFT/JAR', 'Specify special path to server.') do |jar|
    options[:jar] = jar
  end

  opts.on_tail('-h', '--help', 'Show this message') do
    puts opts
    exit
  end

end.parse!

log = Logger.new STDOUT
log.level = options[:verbose] ? Logger::DEBUG : Logger::INFO

begin
  pid = File.open(PIDFILE, 'r') { |f| f.read }
rescue Errno::ENOENT => e
  log.warn e.message
  log.warn "No pidfile found. Creating one."
  pid = nil
end

file = File.open(PIDFILE, 'w+')

if options[:stop]
  if pid.nil? or pid.empty?
    log.error "No existing process found. Terminating."
  else
    pid = pid.to_i
    begin
      Process.kill 'HUP', pid
      log.info "Found existing process ID # #{pid}. Terminating."
    rescue Errno::ESRCH => e
      log.error "Found process ID # #{pid}, but it is not running. Terminating."
    end
  end

  file.puts ''
  exit
end

segments = [
  "java",
  "-Xmx#{options[:memory]}M",
  "-Xms#{options[:memory]}M",
  "-jar",
  options[:jar],
  ['nogui'].join(' '),
]
command = segments.join ' '

log.info "Starting Minecraft server with #{options[:memory]}M memory."

pid = spawn command, :err => "/dev/null", :out => "/dev/null"
file.puts pid
Process.detach pid

log.info "Minecraft server started with process ID # #{pid}."