def cpu
      cpus = []
      procfs_file("stat") do |file|
        file.read.scan(CPU_DATA) do |i, user, nice, system, idle|
          cpus << Cpu.new(i.to_i, user.to_i, system.to_i, nice.to_i, idle.to_i)
        end
      end
      cpus
    end
def cpu
      cpus = []
      procfs_file("stat") do |file|
        file.read.scan(CPU_DATA) do |i, user, nice, system, idle|
          cpus << Cpu.new(i.to_i, user.to_i, system.to_i, nice.to_i, idle.to_i)
        end
      end
      cpus
    end
Fetches the cpu statistics (usage counter for user, nice, system and idle)
 @return [Array<Vmstat::Cpu>] the array of cpu counter
 @example
   Vmstat.cpu # => [#<struct Vmstat::Cpu ...>, #<struct Vmstat::Cpu ...>]