fix

blog/golang/golang-concurrency.md

-# 第二十章 golang 并发编程
+# 第二十章 Golang 并发编程
 
 ## 协程
 
@@ -793,3 +793,308 @@ func main() {
 
 ```
 
+## Ticker
+
+Timer只执行一次，Ticker可以周期的执行
+
+示例
+
+```go
+package main
+
+import (
+    "fmt"
+    "time"
+)
+
+func main() {
+    // 执行五次打印
+    ticker := time.NewTicker(time.Second)
+
+    count := 0
+    for _ = range ticker.C {
+        fmt.Println("ticker")
+        count++
+
+        if count >= 5 {
+            ticker.Stop()
+            break
+        }
+    }
+
+}
+
+```
+
+示例
+
+```go
+package main
+
+import (
+    "fmt"
+    "time"
+)
+
+func main() {
+    ticker := time.NewTicker(time.Second)
+    chanInt := make(chan int)
+
+    // 定时向管道随机发送一个数
+    go func() {
+        for _ = range ticker.C {
+            select {
+            case chanInt <- 1:
+            case chanInt <- 2:
+            case chanInt <- 3:
+            }
+        }
+    }()
+
+    // 接收管道数据
+    sum := 0
+    for v := range chanInt {
+        fmt.Printf("v: %v\n", v)
+        sum += v
+        if sum >= 10 {
+            break
+        }
+    }
+
+}
+
+```
+
+## 原子变量
+
+不加锁示例
+
+```go
+package main
+
+import (
+    "fmt"
+    "time"
+)
+
+var value = 100
+
+func add() {
+    value++
+}
+
+func sub() {
+    value--
+}
+
+func main() {
+
+    for i := 0; i < 100; i++ {
+        go add()
+        go sub()
+    }
+
+    time.Sleep(time.Second * 2)
+    fmt.Printf("value: %v\n", value)
+    // value: 101
+
+}
+
+ ```
+
+ 加锁示例
+
+ ```go
+ package main
+
+import (
+    "fmt"
+    "sync"
+    "time"
+)
+
+var value = 100
+
+var lock sync.Mutex
+
+func add() {
+    lock.Lock()
+    value++
+    lock.Unlock()
+}
+
+func sub() {
+    lock.Lock()
+    value--
+    lock.Unlock()
+}
+
+func main() {
+
+    for i := 0; i < 100; i++ {
+        go add()
+        go sub()
+    }
+
+    time.Sleep(time.Second * 2)
+    fmt.Printf("value: %v\n", value)
+    // value: 100
+
+}
+
+```
+
+atomic示例
+
+cas: compare and swap (old new)
+
+```go
+package main
+
+import (
+    "fmt"
+    "sync/atomic"
+    "time"
+)
+
+var value int32 = 100
+
+func add() {
+    atomic.AddInt32(&value, 1)
+}
+
+func sub() {
+    atomic.AddInt32(&value, -1)
+}
+
+func main() {
+
+    for i := 0; i < 100; i++ {
+        go add()
+        go sub()
+    }
+
+    time.Sleep(time.Second * 2)
+    fmt.Printf("value: %v\n", value)
+    // value: 100
+
+}
+```
+
+## 原子操作详解
+
+atomic 提供的原子操作能够确保任一时刻，只有一个goroutine对变量进行操作
+
+善用atomic能够避免程序中出现大量的锁操作
+
+atomic常见的操作有：
+
+- 增减
+- 载入 read
+- 比较并交换cas
+- 交换
+- 存储 write
+
+### 增减
+
+```go
+package main
+
+import (
+    "fmt"
+    "sync/atomic"
+)
+
+func main() {
+
+    var value int32 = 100
+    atomic.AddInt32(&value, 1)
+    fmt.Printf("value: %v\n", value)
+    // value: 101
+
+    atomic.AddInt32(&value, -1)
+    fmt.Printf("value: %v\n", value)
+    // value: 100
+
+}
+
+```
+
+### 读写
+
+```go
+package main
+
+import (
+    "fmt"
+    "sync/atomic"
+)
+
+func main() {
+
+    var value int32 = 100
+
+    // read
+    atomic.LoadInt32(&value)
+    fmt.Printf("value: %v\n", value)
+    // value: 100
+
+    // write
+    atomic.StoreInt32(&value, 200)
+    fmt.Printf("value: %v\n", value)
+    // value: 200
+
+}
+
+```
+
+### 比较并交换cas
+
+```go
+package main
+
+import (
+    "fmt"
+    "sync/atomic"
+)
+
+func main() {
+
+    var value int32 = 100
+
+    // cas
+    ret := atomic.CompareAndSwapInt32(&value, 100, 200)
+
+    fmt.Printf("ret: %v\n", ret)
+    // ret: true
+
+    fmt.Printf("value: %v\n", value)
+    // value: 200
+
+}
+
+```
+
+### 交换
+
+```go
+package main
+
+import (
+    "fmt"
+    "sync/atomic"
+)
+
+func main() {
+
+    var value int32 = 100
+
+    // 直接交换
+    atomic.SwapInt32(&value, 200)
+
+    fmt.Printf("value: %v\n", value)
+    // value: 200
+
+}
+
+```

blog/golang/golang-standard.md

+# 第二十一章 Golang标准库
+
+标准库文档：https://pkg.go.dev/std
+
+## os模块
+
+os模块实现了平台无关的编程接口
+
+
+创建文件
+
+```go
+package main
+
+import (
+    "fmt"
+    "os"
+)
+
+func main() {
+    // 会覆盖原有文件
+    file, err := os.Create("demo.txt")
+
+    if err != nil {
+        fmt.Printf("err: %v\n", err)
+    } else {
+        fmt.Printf("file.Name(): %v\n", file.Name())
+        // file.Name(): demo.txt
+    }
+}
+
+```
+
+创建目录
+
+```go
+package main
+
+import (
+    "fmt"
+    "os"
+)
+
+func main() {
+
+    // 权限777
+    err := os.Mkdir("demo", os.ModePerm)
+
+    if err != nil {
+        fmt.Printf("err: %v\n", err)
+    }
+}
+
+```
+
+创建多级目录
+
+```go
+package main
+
+import (
+    "fmt"
+    "os"
+)
+
+func main() {
+
+    // 权限777
+    err := os.MkdirAll("a/b/demo", os.ModePerm)
+
+    if err != nil {
+        fmt.Printf("err: %v\n", err)
+    }
+}
+
+```
+
+移除文件或空目录
+
+```go
+package main
+
+import (
+    "fmt"
+    "os"
+)
+
+func main() {
+
+    err := os.Remove("demo.txt")
+
+    if err != nil {
+        fmt.Printf("err: %v\n", err)
+    }
+}
+
+```
+
+移除目录下所有文件
+
+```go
+package main
+
+import (
+    "fmt"
+    "os"
+)
+
+func main() {
+
+    err := os.RemoveAll("a")
+
+    if err != nil {
+        fmt.Printf("err: %v\n", err)
+    }
+}
+```
+
+工作目录
+
+```go
+package main
+
+import (
+    "fmt"
+    "os"
+)
+
+func main() {
+
+    // 获取当前工作目录
+    dir, _ := os.Getwd()
+
+    fmt.Printf("dir: %v\n", dir)
+    // dir: /Users/mo/Desktop/go_code
+
+    // 修改当前工作目录
+    os.Chdir("../")
+
+    // 再次获取当前工作目录
+    dir, _ = os.Getwd()
+
+    fmt.Printf("dir: %v\n", dir)
+    // dir: /Users/mo/Desktop
+}
+
+```
+
+获取临时目录
+
+```go
+package main
+
+import (
+    "fmt"
+    "os"
+)
+
+func main() {
+    temp := os.TempDir()
+    fmt.Printf("temp: %v\n", temp)
+    // temp: /var/folders/43/llymqbps19d74q2h_bgb00mr0000gn/T/
+}
+
+```
+
+重命名文件
+
+```go
+package main
+
+import (
+    "fmt"
+    "os"
+)
+
+func main() {
+    err := os.Rename("demo.txt", "demo.2.txt")
+    if err != nil {
+        fmt.Printf("err: %v\n", err)
+    }
+}
+
+```
+
+读取文件
+
+```go
+package main
+
+import (
+    "fmt"
+    "os"
+)
+
+func main() {
+    content, err := os.ReadFile("demo.txt")
+    if err != nil {
+        fmt.Printf("err: %v\n", err)
+    } else {
+        fmt.Printf("content: %v\n", string(content[:]))
+        // content: Hello World
+    }
+}
+
+```
+
+写文件
+
+```go
+package main
+
+import (
+    "fmt"
+    "os"
+)
+
+func main() {
+    err := os.WriteFile("demo.txt", []byte("hello"), os.ModePerm)
+    if err != nil {
+        fmt.Printf("err: %v\n", err)
+    }
+}
+
+```
\ No newline at end of file

blog/golang/index.md

@@ -36,9 +36,9 @@
 
 [第十四章 Golang map](/blog/golang/golang-map.md)
 
-[第十五章 Golang 函数](/blog/golang/golang-function.md)
+[第十五章 Golang 函数 func](/blog/golang/golang-function.md)
 
-[第十六章 Golang 指针](/blog/golang/golang-pointer.md)
+[第十六章 Golang 指针 pointer ](/blog/golang/golang-pointer.md)
 
 [第十七章 Golang 结构体 struct](/blog/golang/golang-struct.md)
 
@@ -46,11 +46,12 @@
 
 [第十九章 Golang包 package](/blog/golang/golang-package.md)
 
-[第二十章 golang 并发编程](/blog/golang/golang-concurrency.md)
+[第二十章 Golang 并发编程](/blog/golang/golang-concurrency.md)
 
+[第二十一章 Golang标准库](/blog/golang/golang-standard.md)
 
-https://www.bilibili.com/video/BV1ME411Y71o?p=27&spm_id_from=pageDriver&vd_source=efbb4dc944fa761b6e016ce2ca5933da
 
+https://www.bilibili.com/video/BV1ME411Y71o?p=27&spm_id_from=pageDriver&vd_source=efbb4dc944fa761b6e016ce2ca5933da
 
 
-https://www.bilibili.com/video/BV1zR4y1t7Wj/?p=75&spm_id_from=pageDriver&vd_source=efbb4dc944fa761b6e016ce2ca5933da
+https://www.bilibili.com/video/BV1zR4y1t7Wj/?p=78&spm_id_from=pageDriver&vd_source=efbb4dc944fa761b6e016ce2ca5933da
\ No newline at end of file