Prints CPU(s) usage and updates it in real time by accessing the CPU info in /proc/stat

cpuinfo.go

package main

import (
	"os"
	"log"
	"bufio"
	"strconv"
	"strings"
	"runtime"
	"time"
	tm "github.com/buger/goterm" // `go get github.com/buger/goterm`
)

type cpu_val struct {
	idle int
	total int
}

func main() {
	tm.Clear()
	num_CPU := runtime.NumCPU()
	tm.MoveCursor(1,1)
	tm.Println("Nbr of CPU(s):", num_CPU)
	file, err := os.Open("/proc/stat")
	check(err)
	reader := bufio.NewReader(file)
	reader.ReadString('\n')
	var cpu_infos_prev = make([]cpu_val, num_CPU)
	for i:=0; i<num_CPU; i++ {
		cpu_line, err := reader.ReadString('\n')
		check(err)
		idle, total := getValues(cpu_line)
		var new_cpu_val = cpu_val {idle, total}
		cpu_infos_prev = append(cpu_infos_prev, new_cpu_val)
	}
	for {
		time.Sleep(1 * time.Second)
		file, err = os.Open("/proc/stat")
		check(err)
		reader = bufio.NewReader(file)
		reader.ReadString('\n')
		for i:=0; i<num_CPU; i++ {
			cpu_line, err := reader.ReadString('\n')
			check(err)
			idle, total := getValues(cpu_line)
			diff_total := total - cpu_infos_prev[i].total + 1 // to avoid div by 0
			diff_idle := idle - cpu_infos_prev[i].idle
			percentage := 100*(float64(diff_total - diff_idle)/float64(diff_total))
			cpu_infos_prev[i].total = total
			cpu_infos_prev[i].idle = idle
			tm.MoveCursor(1, i+2)
			tm.Printf("CPU %d: %.1f%%  ", i+1, percentage)
		}
		tm.Printf("\n")
		tm.Flush()
	}
}

func check(err error) {
	if err != nil {
		log.Fatal(err)
	}
}

func getValues(cpu string) (int, int) {
	values := strings.Split(cpu, " ")
	total := 0
	idle := 0
	for i:=1; i<len(values); i++ {
		new_val, err := strconv.Atoi(strings.Replace(values[i], "\n", "", 1))
		check(err)
		total += new_val
		if i==4 {
			idle = new_val
		}
	}
	return idle, total
}