练习 8.9： 编写一个du工具，每隔一段时间将root目录下的目录大小计算并显示出来。
代码语言：javascript复制package main
import (
// "filepath"
"flag"
"fmt"
"io/ioutil"
"os"
"path"
"sync"
"time"
)
/*
练习 8.9： 编写一个du工具，每隔一段时间将root目录下的目录大小计算并显示出来。
*/
//接收命令行参数-v
var verbose = flag.Bool("v", false, "show verbose progress messages")
func main() {
//接收命令行参数,多个路径
flag.Parse()
roots := flag.Args()
//如果没传递任何路径,给默认值
if len(roots) == 0 {
roots = []string{"/"}
}
for {
sumFileSize(roots)
time.Sleep(20 * time.Second)
}
}
func sumFileSize(roots []string) {
//发送和接收文件字节大小的channel
fileSizes := make(chan int64)
//goroutine的计数器
var n sync.WaitGroup
//循环命令行传递的路径
for _, root := range roots {
n.Add(1)
//启动goroutine计算
go walkDir(root, &n, fileSizes)
}
//启动goroutine,等待所有计算目录的goroutine结束
go func() {
n.Wait()
close(fileSizes)
}()
//定时显示目录进度发送的channel
var tick <-chan time.Time
if *verbose {
tick = time.Tick(500 * time.Millisecond)
}
var nfiles, nbytes int64
//select和loop循环,多路复用
loop:
for {
select {
case size, ok := <-fileSizes:
if !ok {
break loop // fileSizes was closed
}
//计算目录数,计算字节大小
nfiles
nbytes = size
case <-tick:
//接收到定时channel打印进度
printDiskUsage(nfiles, nbytes)
}
}
//最后打印总计
printDiskUsage(nfiles, nbytes) // final totals
}
func walkDir(dir string, n *sync.WaitGroup, fileSizes chan<- int64) {
defer n.Done()
for _, entry := range dirents(dir) {
if entry.IsDir() {
n.Add(1)
subdir := path.Join(dir, entry.Name())
//开启多个goroutine进行递归
go walkDir(subdir, n, fileSizes)
} else {
fileSizes <- entry.Size()
}
}
}
var sema = make(chan struct{}, 20)
// dirents returns the entries of directory dir.
func dirents(dir string) []os.FileInfo {
//使用计数信号量逻辑限制太多并发
sema <- struct{}{}
entries, err := ioutil.ReadDir(dir)
<-sema
if err != nil {
fmt.Fprintf(os.Stderr, "du1: %vn", err)
return nil
}
return entries
}
func printDiskUsage(nfiles, nbytes int64) {
fmt.Printf("%d files %.1f GBn", nfiles, float64(nbytes)/1e9)
}
