#!/bin/bash
set -Eeuo pipefail

# see /proc/stat in proc(5)
# user nice system idle iowait irq softirq steal guest guest_nice
declare -a last_cpu_stats=( 0 0 0 0 0 0 0 0 0 0 )
declare -a cpu_usage=( 0 0 0 0 0 0 0 0 0 0 )

function gather_cpu_usage () {
  local cpu_stats=( $(read head numbers < /proc/stat; echo "$numbers") )
  local i
  for i in ${!cpu_usage[@]}; do
    cpu_usage[$i]=$((cpu_stats[$i] - last_cpu_stats[$i]))
  done
  
  last_cpu_stats=( ${cpu_stats[@]} )
}

gather_cpu_usage
sleep 2
echo "${cpu_usage[@]}"
gather_cpu_usage
echo "${last_cpu_stats[@]}"

echo "${cpu_usage[@]}"