increment

# File activesupport/lib/active_support/cache/file_store.rb, line 38
      def increment(name, amount = 1, options = nil)
        file_name = key_file_path(namespaced_key(name, options))
        lock_file(file_name) do
          options = merged_options(options)
          if num = read(name, options)
            num = num.to_i + amount
            write(name, num, options)
            num
          else
            nil
          end
        end
      end