package main
import "fmt"
func f(msg string) {
fmt.Println(msg)
}
func main(){
go f("goroutine")
go func(msg string) {
fmt.Println(msg)
}("going")
}
package main
import "fmt"
import "time"
import "math/rand"
func routine(name string, delay time.Duration) {
t0 := time.Now()
fmt.Println(name, " start at ", t0)
time.Sleep(delay)
t1 := time.Now()
fmt.Println(name, " end at ", t1)
fmt.Println(name, " lasted ", t1.Sub(t0))
}
func main() {
//生成随机种子
rand.Seed(time.Now().Unix())
var name string
for i:=0; i<3; i++{
name = fmt.Sprintf("go_%02d", i) //生成ID
//生成随机等待时间,从0-4秒
go routine(name, time.Duration(rand.Intn(5)) * time.Second)
}
//让主进程停住,不然主进程退了,goroutine也就退了
var input string
fmt.Scanln(&input)
fmt.Println("done")
}
go_00 start at 2012-11-04 19:46:35.8974894 +0800 +0800
go_01 start at 2012-11-04 19:46:35.8974894 +0800 +0800
go_02 start at 2012-11-04 19:46:35.8974894 +0800 +0800
go_01 end at 2012-11-04 19:46:36.8975894 +0800 +0800
go_01 lasted 1.0001s
go_02 end at 2012-11-04 19:46:38.8987895 +0800 +0800
go_02 lasted 3.0013001s
go_00 end at 2012-11-04 19:46:39.8978894 +0800 +0800
go_00 lasted 4.0004s
import "runtime"
...
runtime.GOMAXPROCS(4)
package main
import "fmt"
import "time"
import "math/rand"
import "runtime"
var total_tickets int32 = 10;
func sell_tickets(i int){
for{
if total_tickets > 0 { //如果有票就卖
time.Sleep( time.Duration(rand.Intn(5)) * time.Millisecond)
total_tickets-- //卖一张票
fmt.Println("id:", i, " ticket:", total_tickets)
}else{
break
}
}
}
func main() {
runtime.GOMAXPROCS(4) //我的电脑是4核处理器,所以我设置了4
rand.Seed(time.Now().Unix()) //生成随机种子
for i := 0; i < 5; i++ { //并发5个goroutine来卖票
go sell_tickets(i)
}
//等待线程执行完
var input string
fmt.Scanln(&input)
fmt.Println(total_tickets, "done") //退出时打印还有多少票
}
$ go run sell_tickets.go
id: 0 ticket: 9
id: 0 ticket: 8
id: 4 ticket: 7
id: 1 ticket: 6
id: 3 ticket: 5
id: 0 ticket: 4
id: 3 ticket: 3
id: 2 ticket: 2
id: 0 ticket: 1
id: 3 ticket: 0
id: 1 ticket: -1
id: 4 ticket: -2
id: 2 ticket: -3
id: 0 ticket: -4
-4 done
package main
import (
"fmt"
"runtime"
"math/rand"
"time"
"sync"
)
var total_tickets int32 = 10;
var mutex = &sync.Mutex{}
func sell_tickets(i int){
for total_tickets>0 {
mutex.Lock()
if total_tickets > 0 { //如果有票就卖
time.Sleep( time.Duration(rand.Intn(5)) * time.Millisecond)
total_tickets-- //卖一张票
fmt.Println("id:", i, " ticket:", total_tickets)
} else{
break
}
mutex.Unlock()
}
}
func main() {
runtime.GOMAXPROCS(4) //我的电脑是4核处理器,所以我设置了4
rand.Seed(time.Now().Unix()) //生成随机种子
for i := 0; i < 5; i++ { //并发5个goroutine来卖票
go sell_tickets(i)
}
//等待线程执行完
var input string
fmt.Scanln(&input)
fmt.Println(total_tickets, "done") //退出时打印还有多少票
}
下面使用了atomic操作,所以是安全的
package main
import "fmt"
import "time"
import "sync/atomic"
func main() {
var cnt uint32 = 0
for i := 0; i < 10; i++ {
go func() {
for i:=0; i<20; i++ {
time.Sleep(time.Millisecond)
atomic.AddUint32(&cnt, 1)
}
}()
}
time.Sleep(time.Second)//等一秒钟等goroutine完成
cntFinal := atomic.LoadUint32(&cnt)//取数据
fmt.Println("cnt:", cntFinal)
}
Channal是什么?Channal就是用来通信的,就像Unix下的管道一样,在Go中是这样使用Channel的。
package main
import "fmt"
func main() {
//创建一个string类型的channel
channel := make(chan string)
//创建一个goroutine向channel里发一个字符串
go func() { channel <- "hello" }()
msg := <- channel
fmt.Println(msg)
package main
import "fmt"
func main() {
channel := make(chan string, 2)
go func() {
channel <- "hello"
channel <- "World"
}()
msg1 := <-channel
msg2 := <-channel
fmt.Println(msg1, msg2)
}
channel默认上是阻塞的,也就是说,如果Channel满了,就阻塞写,如果Channel空了,就阻塞读。于是,我们就可以使用这种特性来同步我们的发送和接收端。
package main
import "fmt"
import "time"
func main() {
channel := make(chan string) //注意: buffer为1
go func() {
channel <- "hello"
fmt.Println("write \"hello\" done!")
channel <- "World" //Reader在Sleep,这里在阻塞
fmt.Println("write \"World\" done!")
fmt.Println("Write go sleep...")
time.Sleep(3*time.Second)
channel <- "channel"
fmt.Println("write \"channel\" done!")
}()
time.Sleep(2*time.Second)
fmt.Println("Reader Wake up...")
msg := <-channel
fmt.Println("Reader: ", msg)
msg = <-channel
fmt.Println("Reader: ", msg)
msg = <-channel //Writer在Sleep,这里在阻塞
fmt.Println("Reader: ", msg)
}
Reader Wake up...
Reader: hello
write "hello" done!
write "World" done!
Write go sleep...
Reader: World
write "channel" done!
Reader: channel
Channel阻塞的这个特性还有一个好处是,可以让我们的goroutine在运行的一开始就阻塞在从某个channel领任务,这样就可以作成一个类似于线程池一样的东西。
package main
import "time"
import "fmt"
func main() {
//创建两个channel - c1 c2
c1 := make(chan string)
c2 := make(chan string)
//创建两个goruntine来分别向这两个channel发送数据
go func() {
time.Sleep(time.Second * 1)
c1 <- "Hello"
}()
go func() {
time.Sleep(time.Second * 1)
c2 <- "World"
}()
//使用select来侦听两个channel
for i := 0; i < 2; i++ {
select {
case msg1 := <-c1:
fmt.Println("received", msg1)
case msg2 := <-c2:
fmt.Println("received", msg2)
}
}
}
注意:上面的select是阻塞的,所以,才搞出ugly的for i <2这种东西。
解决上述那个for循环的问题,一般有两种方法:一种是阻塞但有timeout,一种是无阻塞。我们来看看如果给select设置上timeout的。
for {
timeout_cnt := 0
select {
case msg1 := <-c1:
fmt.Println("msg1 received", msg1)
case msg2 := <-c2:
fmt.Println("msg2 received", msg2)
case <-time.After(time.Second * 30):
fmt.Println("Time Out")
timout_cnt++
}
if time_cnt > 3 {
break
}
上面代码中高亮的代码主要是用来让select返回的,注意 case中的time.After事件。
for {
select {
case msg1 := <-c1:
fmt.Println("received", msg1)
case msg2 := <-c2:
fmt.Println("received", msg2)
default: //default会导致无阻塞
fmt.Println("nothing received!")
time.Sleep(time.Second)
}
}
关闭Channel可以通知对方内容发送完了,不用再等了。
package main
import "fmt"
import "time"
import "math/rand"
func main() {
channel := make(chan string)
rand.Seed(time.Now().Unix())
//向channel发送随机个数的message
go func () {
cnt := rand.Intn(10)
fmt.Println("message cnt :", cnt)
for i:=0; i<cnt; i++{
channel <- fmt.Sprintf("message-%2d", i)
}
close(channel) //关闭Channel
}()
var more bool = true
var msg string
for more {
select{
//channel会返回两个值,一个是内容,一个是还有没有内容
case msg, more = <- channel:
if more {
fmt.Println(msg)
}else{
fmt.Println("channel closed!")
}
}
}
}
message cnt : 0
channel closed!
Go语言中可以使用time.NewTimer或time.NewTicker来设置一个定时器,这个定时器会绑定在你的当前channel中,通过channel的阻塞通知机器来通知你的程序。
package main
import "time"
import "fmt"
func main() {
timer := time.NewTimer(2*time.Second)
<- timer.C
fmt.Println("timer expired!")
}
package main
import "time"
import "fmt"
func main() {
ticker := time.NewTicker(time.Second)
for t := range ticker.C {
fmt.Println("Tick at", t)
}
}
上面的这个ticker会让你程序进入死循环,我们应该放其放在一个goroutine中。下面这个程序结合了timer和ticker
package main
import "time"
import "fmt"
func main() {
ticker := time.NewTicker(time.Second)
go func () {
for t := range ticker.C {
fmt.Println(t)
}
}()
//设置一个timer,10钞后停掉ticker
timer := time.NewTimer(10*time.Second)
<- timer.C
ticker.Stop()
fmt.Println("timer expired!")
}
一个Echo Server的Socket代码
package main
import (
"net"
"fmt"
"io"
)
const RECV_BUF_LEN = 1024
func main() {
listener, err := net.Listen("tcp", "0.0.0.0:6666")//侦听在6666端口
if err != nil {
panic("error listening:"+err.Error())
}
fmt.Println("Starting the server")
for {
conn, err := listener.Accept() //接受连接
if err != nil {
panic("Error accept:"+err.Error())
}
fmt.Println("Accepted the Connection :", conn.RemoteAddr())
go EchoServer(conn)
}
}
func EchoServer(conn net.Conn) {
buf := make([]byte, RECV_BUF_LEN)
defer conn.Close()
for {
n, err := conn.Read(buf);
switch err {
case nil:
conn.Write( buf[0:n] )
case io.EOF:
fmt.Printf("Warning: End of data: %s \n", err);
return
default:
fmt.Printf("Error: Reading data : %s \n", err);
return
}
}
}
package main
import (
"fmt"
"time"
"net"
)
const RECV_BUF_LEN = 1024
func main() {
conn,err := net.Dial("tcp", "127.0.0.1:6666")
if err != nil {
panic(err.Error())
}
defer conn.Close()
buf := make([]byte, RECV_BUF_LEN)
for i := 0; i < 5; i++ {
//准备要发送的字符串
msg := fmt.Sprintf("Hello World, %03d", i)
n, err := conn.Write([]byte(msg))
if err != nil {
println("Write Buffer Error:", err.Error())
break
}
fmt.Println(msg)
//从服务器端收字符串
n, err = conn.Read(buf)
if err !=nil {
println("Read Buffer Error:", err.Error())
break
}
fmt.Println(string(buf[0:n]))
//等一秒钟
time.Sleep(time.Second)
}
}
Go语言那么C,所以,一定会有一些系统调用。Go语言主要是通过两个包完成的。一个是os包,一个是syscall包。(注意,链接被墙) 这两个包里提供都是Unix-Like的系统调用
syscall包的东西我不举例了,大家可以看看《Unix高级环境编程》一书。
环境变量
package main
import "os"
import "strings"
func main() {
os.Setenv("WEB", "https://coolshell.cn") //设置环境变量
println(os.Getenv("WEB")) //读出来
for _, env := range os.Environ() { //穷举环境变量
e := strings.Split(env, "=")
println(e[0], "=", e[1])
}
}
package main
import "os/exec"
import "fmt"
func main() {
cmd := exec.Command("ping", "127.0.0.1")
out, err := cmd.Output()
if err!=nil {
println("Command Error!", err.Error())
return
}
fmt.Println(string(out))
}
package main
import (
"strings"
"bytes"
"fmt"
"log"
"os/exec"
)
func main() {
cmd := exec.Command("tr", "a-z", "A-Z")
cmd.Stdin = strings.NewReader("some input")
var out bytes.Buffer
cmd.Stdout = &out
err := cmd.Run()
if err != nil {
log.Fatal(err)
}
fmt.Printf("in all caps: %q\n", out.String())
}
Go语言中处理命令行参数很简单:(使用os的Args就可以了)
func main() {
args := os.Args
fmt.Println(args) //带执行文件的
fmt.Println(args[1:]) //不带执行文件的
}
C:\Projects\Go> go run args.go aaa bbb ccc ddd
[C:\Users\haoel\AppData\Local\Temp\go-build742679827\command-line-arguments\_
obj\a.out.exe aaa bbb ccc ddd]
[aaa bbb ccc ddd]
那么,如果我们要搞出一些像 mysql -uRoot -hLocalhost -pPwd 或是像 cc -O3 -Wall -o a a.c 这样的命令行参数我们怎么办?Go提供了一个package叫flag可以容易地做到这一点
package main
import "flag"
import "fmt"
func main() {
//第一个参数是“参数名”,第二个是“默认值”,第三个是“说明”。返回的是指针
host := flag.String("host", "coolshell.cn", "a host name ")
port := flag.Int("port", 80, "a port number")
debug := flag.Bool("d", false, "enable/disable debug mode")
//正式开始Parse命令行参数
flag.Parse()
fmt.Println("host:", *host)
fmt.Println("port:", *port)
fmt.Println("debug:", *debug)
}
执行起来会是这个样子:
#如果没有指定参数名,则使用默认值
$ go run flagtest.go
host: coolshell.cn
port: 80
debug: false
#指定了参数名后的情况
$ go run flagtest.go -host=localhost -port=22 -d
host: localhost
port: 22
debug: true
#用法出错了(如:使用了不支持的参数,参数没有=)
$ go build flagtest.go
$ ./flagtest -debug -host localhost -port=22
flag provided but not defined: -debug
Usage of flagtest:
-d=false: enable/disable debug mode
-host="coolshell.cn": a host name
-port=80: a port number
exit status 2
package main
import (
"fmt"
"net/http"
"io/ioutil"
"path/filepath"
)
const http_root = "/home/haoel/coolshell.cn/"
func main() {
http.HandleFunc("/", rootHandler)
http.HandleFunc("/view/", viewHandler)
http.HandleFunc("/html/", htmlHandler)
http.ListenAndServe(":8080", nil)
}
//读取一些HTTP的头
func rootHandler(w http.ResponseWriter, r *http.Request) {
fmt.Fprintf(w, "rootHandler: %s\n", r.URL.Path)
fmt.Fprintf(w, "URL: %s\n", r.URL)
fmt.Fprintf(w, "Method: %s\n", r.Method)
fmt.Fprintf(w, "RequestURI: %s\n", r.RequestURI )
fmt.Fprintf(w, "Proto: %s\n", r.Proto)
fmt.Fprintf(w, "HOST: %s\n", r.Host)
}
//特别的URL处理
func viewHandler(w http.ResponseWriter, r *http.Request) {
fmt.Fprintf(w, "viewHandler: %s", r.URL.Path)
}
//一个静态网页的服务示例。(在http_root的html目录下)
func htmlHandler(w http.ResponseWriter, r *http.Request) {
fmt.Printf("htmlHandler: %s\n", r.URL.Path)
filename := http_root + r.URL.Path
fileext := filepath.Ext(filename)
content, err := ioutil.ReadFile(filename)
if err != nil {
fmt.Printf(" 404 Not Found!\n")
w.WriteHeader(http.StatusNotFound)
return
}
var contype string
switch fileext {
case ".html", "htm":
contype = "text/html"
case ".css":
contype = "text/css"
case ".js":
contype = "application/javascript"
case ".png":
contype = "image/png"
case ".jpg", ".jpeg":
contype = "image/jpeg"
case ".gif":
contype = "image/gif"
default:
contype = "text/plain"
}
fmt.Printf("ext %s, ct = %s\n", fileext, contype)
w.Header().Set("Content-Type", contype)
fmt.Fprintf(w, "%s", content)
}
Go的功能库有很多,大家自己慢慢看吧。
查阅转发的这篇文章,看了这么多,有些我都是懵的... ...
本文作者为陈皓,转载请注明。