Screen sessions + databases on a per-project basis, isolated in separate volumes

db.rb

#!/usr/bin/env ruby

require 'optparse'
begin
  require 'open4'
rescue LoadError => ex
  begin
    require 'rubygems'
    require 'open4'
  rescue LoadError
    raise ex
  end
end

class DbServer
  class Error < RuntimeError; end

  attr_accessor :datadir

  def initialize(datadir)
    self.datadir = datadir
  end

  def start
    @pid = Open4.bg(start_command, :stdout => $stdout, :stderr => $stderr).pid
  end

  def stop
    Open4.maim(@pid)
  end

  def running?
    begin
      Process.kill(0, @pid)
      return true
    rescue Errno::ESRCH
      return false
    end
  end
end

class MySQL < DbServer
  def installdb
    system 'which -s mysql_install_db'
    raise DbServer::Error, "Unable to find mysql_install_db. Please make sure it's in your PATH before trying again." unless $?.success?
    system 'mysql_install_db', "--datadir=#{datadir}"
    raise DbServer::Error, "There was a problem creating the database files at #{datadir}." unless $?.success?
  end

  def start_command
    "mysqld --datadir=#{datadir}"
  end
end

class DbCLI
  attr_reader :args

  def initialize(args)
    @args = args
    parser.parse!(args)
  end

  def run
    begin
      case args.first
      when 'install'
        server.installdb
      when 'run', nil
        trap(:INT) { server.stop; exit }
        server.start
        sleep 1 while server.running?
      else
        $stderr.puts "#{$0}: error: unknown subcommand #{args.first.inspect}"
        exit(-1)
      end
    rescue DbServer::Error => ex
      $stderr.puts ex.message
      exit(-1)
    end
  end

  def server
    @server ||= begin
      if not @datadir
        puts parser
        exit 1
      end
      MySQL.new(@datadir)
    end
  end

  def self.run(args)
    new(args).run
  end

  private

  def parser
    @parser ||= OptionParser.new do |opts|
      opts.banner = "Usage: #{$0} (run|install) [options]"

      opts.on('-p', '--project=NAME', 'which project to start the database with (required)') do |name|
        @datadir = "/Volumes/#{name}/Data/MySQL/5.0"
      end

      opts.on('-D', '--datadir=PATH', 'which directory to use for the data') do |datadir|
        @datadir = datadir
      end

      opts.on('-h', '--help', 'show this message') do
        puts opts
        exit
      end
    end
  end
end


DbCLI.run(ARGV)

s.rb

#!/usr/bin/env ruby -w
require 'pathname'

this = File.basename($0)
name = ARGV.shift
volumes = Pathname.glob('/Volumes/*')
volume_names = volumes.map{|v| v.basename.to_s }.join(', ')

if name.nil? || name.empty?
  abort "#{this}: please provide one of #{volume_names}"
end

if closest_match = volumes.select {|vol| vol.basename.to_s.downcase.index(name.downcase) == 0 }.min
  screenrc = closest_match + '.screenrc'
  if screenrc.exist?
    args = ARGV.map {|a| %{"#{a}"} }.join(' ')
    exec %{screen -U -A -S #{closest_match.basename} -c #{screenrc} -xRR #{args}}
  else
    abort "#{this}: no .screenrc found in #{closest_match}"
  end
else
  abort "#{this}: no volume found matching #{name}, please provide one of #{volume_names}"
end