Log reader can tail logs and will restart logs that have been rotated. Subclass and replace the `process` method!

log_reader.rb

class LogReader
  def self.open filename
    new File.open filename, 'r'
  end

  def initialize file
    raise ArgumentError, 'File required!' unless File === file
    @file = file
  end
  attr :file

  def tail
    loop do
      wait
      line = file.gets
      process line
    end
  ensure
    file.close
  end

  protected

  def process line
    puts line
  end

  def wait
    until readable? do
      sleep 1
    end
  end

  def readable?
    raise EOFError, 'File deleted or changed.' if altered?
    get && unget && true
  rescue EOFError
    reopen!
  end

  def get
    file.getbyte
  end

  def unget
    file.pos = file.pos - 1
  end

  def reopen!
    return nil unless exists?

    save_restore_pos do
      file.reopen file.path, 'r'
    end
  end

  def save_restore_pos active = same?
    cursor = file.pos if active
    yield
    file.pos = cursor if active
    file
  end

  def altered?
    !(exists? && same?)
  end

  def exists?
    File.exists? file.path
  end

  def same?
    File.stat(file.path).ino == file.stat.ino
  end
end

log = LogReader.open '~test'
log.tail

~output

foo
bar

~test

foo
bar