Keep directories synced

keep-synced.rb

require 'pathname'

src = ARGV[0]
dst = ARGV[1]

src = "#{src}/" unless src.end_with?("/")
dst = "#{dst}/" unless dst.end_with?("/")

src = Pathname.new(src)
dst = Pathname.new(dst)

RSYNC_OPTS = %w[
  -ai
  --del
  --stats
]

def rsync src, dst
  system 'rsync', *RSYNC_OPTS, src.to_s, dst.to_s
end

mutex = Mutex.new
cond = ConditionVariable.new
has_pending_changes = true

io = IO.popen(['fswatch', '-or', src.to_s])

th1 = Thread.new do
  while io.gets
    mutex.synchronize do
      has_pending_changes = true
      cond.signal
    end
  end
end

th2 = Thread.new do
  loop do
    mutex.synchronize do
      until has_pending_changes do
        cond.wait(mutex)
      end

      puts "Detected changes, rsyncing '#{src}' to '#{dst}'"

      has_pending_changes = false
      if File.directory?(src)
        rsync src, dst
      else
        puts "'#{src}' not found; skipping"
      end
    end
  end
end

th1.join
th2.join