add cpu monitor for linux

os_linux.go

@@ -3,6 +3,8 @@
 package staros
 
 import (
+	"fmt"
+	"io/ioutil"
 	"os/user"
 	"strconv"
 	"strings"
@@ -64,3 +66,41 @@ func Whoami() (uid, gid int, uname, gname, home string, err error) {
 	gname = gup.Name
 	return
 }
+
+func getCPUSample() (idle, total uint64) {
+	contents, err := ioutil.ReadFile("/proc/stat")
+	if err != nil {
+		return
+	}
+	lines := strings.Split(string(contents), "\n")
+	for _, line := range lines {
+		fields := strings.Fields(line)
+		if fields[0] == "cpu" {
+			numFields := len(fields)
+			for i := 1; i < numFields; i++ {
+				val, err := strconv.ParseUint(fields[i], 10, 64)
+				if err != nil {
+					fmt.Println("Error: ", i, fields[i], err)
+				}
+				total += val // tally up all the numbers to get total ticks
+				if i == 4 {  // idle is the 5th field in the cpu line
+					idle = val
+				}
+			}
+			return
+		}
+	}
+	return
+}
+
+// CpuUsage 获取CPU使用量
+func CpuUsage(sleep time.Time) float64 {
+	idle0, total0 := getCPUSample()
+	time.Sleep(sleep)
+	idle1, total1 := getCPUSample()
+	idleTicks := float64(idle1 - idle0)
+	totalTicks := float64(total1 - total0)
+	cpuUsage := 100 * (totalTicks - idleTicks) / totalTicks
+	return cpuUsage
+	//fmt.Printf("CPU usage is %f%% [busy: %f, total: %f]\n", cpuUsage, totalTicks-idleTicks, totalTicks)
+}