logfile_example.rb

require 'tmpdir'

def setup
  dir = Dir::tmpdir
  %w(system.log 20130330.log 20130329.log).each do |fn|
    File.open(fn, 'w') { |f| f.print 'fake contents' }
  end
end

def rotate_logs
  log_filenames = Dir[File.join(Dir::tmpdir, '*.log')]
  rename_latest(log_filenames)
  delete_oldest(log_filenames)
end

def rename_latest(log_filenames)
  # code to rename the latest
end

def delete_oldest(log_filenames)
  # code to delete the latest
end

setup
rotate_logs