add yuheng

Author: xiaolong.ran

defer.go

@@ -0,0 +1,18 @@
+package main
+
+
+import (
+	"fmt"
+)
+
+func main() {
+	defer_call()
+}
+
+func defer_call() {
+	defer func() { fmt.Println("打印前") }()
+	defer func() { fmt.Println("打印中") }()
+	defer func() { fmt.Println("打印后") }()
+
+	panic("触发异常")
+}

file_read.go

@@ -0,0 +1,19 @@
+package main
+
+import (
+	"os"
+	"github.com/davecgh/go-spew/spew"
+)
+
+func main() {
+	tmp := make([]byte, 1)
+	file, err := os.OpenFile("/Users/wolf4j/go/src/golang/read.txt", 1, os.ModePerm)
+	if err != nil {
+		panic("wandan")
+	}
+	n, err := file.Read(tmp)
+	if err != nil {
+		panic("wandan")
+	}
+	spew.Dump(n)
+}

io/opendiskfile.go

@@ -0,0 +1,83 @@
+package main
+
+import (
+	"fmt"
+	"os"
+)
+
+func checkERR(e error) {
+	if e != nil {
+		panic(e)
+	}
+}
+func main() {
+	//dat, err := ioutil.ReadFile("/tmp/dat")
+	//checkERR(err)
+	//fmt.Print(string(dat))
+	////open只是以只读的方式打开
+	//f, err := os.Open("/tmp/dat")
+	//checkERR(err)
+
+	//=============================
+	//openfile
+	// os.O_RDONLY // 只读
+	// os.O_WRONLY // 只写
+	// os.O_RDWR // 读写
+	// os.O_APPEND // 往文件中添建（Append）
+	// os.O_CREATE // 如果文件不存在则先创建
+	// os.O_TRUNC // 文件打开时裁剪文件
+	// os.O_EXCL // 和O_CREATE一起使用，文件不能存在
+	// os.O_SYNC // 以同步I/O的方式打开
+	//f1, err := os.OpenFile("/tmp/eat", os.O_RDONLY, os.ModePerm)
+	//defer f1.Close()
+	//checkERR(err)
+	//ret, err := f1.Seek(3, 0)
+	//bb := make([]byte, 8)
+	//checkERR(err)
+	//n, err := f1.Read(bb)
+	//checkERR(err)
+	//fmt.Printf("ret:%d , read:%d, value: %s", ret, n, string(bb))
+
+	f2, err := os.OpenFile("/tmp/eat", os.O_WRONLY, os.ModePerm)
+	defer f2.Close()
+	checkERR(err)
+	ret2, err := f2.Seek(3, 0)
+	checkERR(err)
+	fmt.Printf("ret2:%d\n", ret2)
+	bb2 := []byte("Bytes\n")
+	nn2, err := f2.Write(bb2)
+	checkERR(err)
+	fmt.Printf("value nn2:%v\n", nn2)
+	ret22, err := f2.Seek(8, 0)
+	checkERR(err)
+	fmt.Printf("ret22:%d\n", ret22)
+	//=============================
+
+	//b1 := make([]byte, 5)
+	//n1, err := f.Read(b1)
+	//checkERR(err)
+	//fmt.Printf("%d bytes: %s\n", n1, string(b1))
+	//
+	//o2, err := f.Seek(6, 0)
+	//checkERR(err)
+	//b2 := make([]byte, 2)
+	//n2, err := f.Read(b2)
+	//checkERR(err)
+	//fmt.Printf("%d bytes @ %d: %s\n", n2, o2, string(b2))
+	//
+	//o3, err := f.Seek(6, 0)
+	//checkERR(err)
+	//b3 := make([]byte, 2)
+	//n3, err := io.ReadAtLeast(f, b3, 2)
+	//checkERR(err)
+	//fmt.Printf("%d bytes @ %d: %s\n", n3, o3, string(b3))
+	//
+	//_, err = f.Seek(0, 0)
+	//checkERR(err)
+	//r4 := bufio.NewReader(f)
+	//b4, err := r4.Peek(5)
+	//checkERR(err)
+	//fmt.Printf("5 bytes: %s\n", string(b4))
+	//
+	//f.Close()
+}

mapstruct.go

@@ -0,0 +1,32 @@
+package main
+
+type student struct {
+	Name string
+	Age  int
+}
+
+func pase_student() {
+	m := make(map[string]*student)
+	stus := []student{
+		{Name: "zhou", Age: 24},
+		{Name: "li", Age: 23},
+		{Name: "wang", Age: 22},
+	}
+
+	//错误写法
+	//for _, stu := range stus {
+	//	m[stu.Name] = &stu
+	//}
+
+	for i := 0; i < len(stus); i++ {
+		m[stus[i].Name] = &stus[i]
+	}
+	for k, v := range m {
+		println(k, "=>", v.Name)
+	}
+
+}
+
+func main() {
+	pase_student()
+}

os/gomaxprocs.go

@@ -0,0 +1,26 @@
+package main
+
+import (
+	"runtime"
+	"sync"
+	"fmt"
+)
+
+func main() {
+	runtime.GOMAXPROCS(1)
+	wg := sync.WaitGroup{}
+	wg.Add(20)
+	for i := 0; i < 10; i++ {
+		go func() {
+			fmt.Println("A: ", i)
+			wg.Done()
+		}()
+	}
+	for i := 0; i < 10; i++ {
+		go func(i int) {
+			fmt.Println("B: ", i)
+			wg.Done()
+		}(i)
+	}
+	wg.Wait()
+}

os/pmg

@@ -0,0 +1,33 @@
+package main
+
+import (
+	"sync/atomic"
+	"time"
+	"runtime"
+)
+
+//GODEBUG=schedtrace=1000,scheddetail=1 ./pmg
+//GOMAXPROCS=1 GODEBUG=schedtrace=1000 ./pmg
+
+var count int64
+
+func test() {
+	atomic.AddInt64(&count, 1)
+	defer atomic.AddInt64(&count, -1)
+
+
+	runtime.LockOSThread()
+	defer runtime.LockOSThread()
+
+	time.Sleep(time.Second)//1s
+}
+
+func main() {
+	for i := 0; i <= 2000; i++ {
+		go test()
+	}
+
+	for {
+		time.Sleep(time.Second)
+	}
+}

os/pmg.go

@@ -0,0 +1 @@
+laiba,kuaihuoa

race_conditions.o

@@ -0,0 +1,27 @@
+package main
+
+import "fmt"
+
+type People struct{}
+
+func (p *People) ShowA() {
+	fmt.Println("showA")
+	p.ShowB()
+}
+func (p *People) ShowB() {
+	fmt.Println("showB")
+}
+
+type Teacher struct {
+	People
+}
+
+func (t *Teacher) ShowB() {
+	fmt.Println("teacher showB")
+}
+
+func main() {
+	t := Teacher{}
+	t.ShowA()
+
+}

read.txt

@@ -0,0 +1,13 @@
+package main
+
+import "fmt"
+
+// go build -o hello hello.go
+// file hello
+// ./hello
+func main() {
+	fmt.Println("hello world")
+}
+
+
+//推荐自己去下载源码进行编译，go支持自举，可以使用低版本编译高版本