下面由golang教程栏目给大家介绍一个golang常见库cobra，希望对需要的朋友有所帮助！
cobra 是 go 语言的一个库，可以用于编写命令行工具。通常我们可以看到git pull 、docker container start 、apt install 等等这样命令，都可以很容易用corba来实现，另外，go 语言是很容易编译成一个二进制文件，本文将实现一个简单的命令行工具。
具体写一个例子, 设计一个命令叫blog， 有四个子命令
blog new [post-name] ：创建一篇新的blog blog list ：列出当前有哪些文章 blog delete [post-name]: 删除某一篇文章 blog edit [post-name]：编辑某一篇文章
计划有以下几个步骤
$ go mod init github.com/shalk/blog go: creating new go.mod: module github.com/shalk/blog
说到命令行，可能会想到bash的getopt 或者 java 的jcommand，可以解析各种风格的命令行，但是通常这些命令行都有固定的写法，这个写法一般还记不住要找一个模板参考以下。cobra除了可以解析命令行之外，还提供了命令行，可以生成模板。先安装这个命令行, 并且把库的依赖加到go.mod里
$ go get -u github.com/spf13/cobra/cobra
cobra会安装到$GOPATHbin 目录下，注意环境变量中把它加入PATH中
$ cobra init --pkg-name github.com/shalk/blog -a shalk -l mit Your Cobra applicaton is ready at D:\code\github.com\shalk\blog
目录结构如下:
./cmd ./cmd/root.go ./go.mod ./go.sum ./LICENSE ./main.go
编译一下
go build -o blog .
执行一下
$blog -h A longer description that spans multiple lines and likely contains examples and usage of using your application. For example: Cobra is a CLI library for Go that empowers applications. This application is a tool to generate the needed files to quickly create a Cobra application.
命令行就创建好了，看上去一行代码也不用写，由于随着了解的深入，后面需要调整生成的代码，还是要了解一下cobra代码的套路。
有三个概念，command、flag和args ，例如：
go get -u test.com/a/b
这里 get 就是commond（这里比较特殊）， -u 就是flag， test.com/a/b 就是args
那么命令行就是有三部分构成，所以需要定义好这个
还有一个概念是子命令，比如get就是go的子命令，这是一个树状结构的关系。
我可以使用go命令，也可以使用 go get命令
例如: root.go，定义了root命令，另外在init里面 定义了flag，如果它本身有具体执行，就填充Run字段。
// rootCmd represents the base command when called without any subcommands
var rootCmd = &cobra.Command{
Use: "blog",
Short: "A brief description of your application",
Long: `A longer description that spans multiple lines and likely contains
examples and usage of using your application. For example:
Cobra is a CLI library for Go that empowers applications.
This application is a tool to generate the needed files
to quickly create a Cobra application.`,
// Uncomment the following line if your bare application
// has an action associated with it:
// Run: func(cmd *cobra.Command, args []string) { },
}
// Execute adds all child commands to the root command and sets flags appropriately.
// This is called by main.main(). It only needs to happen once to the rootCmd.
func Execute() {
if err := rootCmd.Execute(); err != nil {
fmt.Println(err)
os.Exit(1)
}
}
func init() {
cobra.OnInitialize(initConfig)
// Here you will define your flags and configuration settings.
// Cobra supports persistent flags, which, if defined here,
// will be global for your application.
rootCmd.PersistentFlags().StringVar(&cfgFile, "config", "", "config file (default is $HOME/.blog.yaml)")
// Cobra also supports local flags, which will only run
// when this action is called directly.
rootCmd.Flags().BoolP("toggle", "t", false, "Help message for toggle")
}如果需要子命令，就需要在init 里，给 rootCmd.AddCommand() 其他的command，其他的子命令通常也会单独用一个文件编写，并且有一个全局变量，让rootCmd可以add它
D:\code\github.com\shalk\blog>cobra add new new created at D:\code\github.com\shalk\blog D:\code\github.com\shalk\blog>cobra add delete delete created at D:\code\github.com\shalk\blog D:\code\github.com\shalk\blog>cobra add list list created at D:\code\github.com\shalk\blog D:\code\github.com\shalk\blog>cobra add edit edit created at D:\code\github.com\shalk\blog
cmd 目录下增加了 new.go, delete.go,list.go,edit.go
new.go
var newCmd = &cobra.Command{
Use: "new",
Short: "create new post",
Long: `create new post `,
Args: func(cmd *cobra.Command, args []string) error {
if len(args) != 1 {
return errors.New("requires a color argument")
}
return nil
},
Run: func(cmd *cobra.Command, args []string) {
fileName := "posts/" + args[0]
err := os.Mkdir("posts", 644)
if err != nil {
log.Fatal(err)
}
_, err = os.Stat( fileName)
if os.IsNotExist(err) {
file, err := os.Create(fileName)
if err != nil {
log.Fatal(err)
}
log.Printf("create file %s", fileName)
defer file.Close()
} else {
}
},
}list.go
var listCmd = &cobra.Command{
Use: "list",
Short: "list all blog in posts",
Long: `list all blog in posts `,
Run: func(cmd *cobra.Command, args []string) {
_, err := os.Stat("posts")
if os.IsNotExist(err) {
log.Fatal("posts dir is not exits")
}
dirs, err := ioutil.ReadDir("posts")
if err != nil {
log.Fatal("read posts dir fail")
}
fmt.Println("------------------")
for _, dir := range dirs {
fmt.Printf(" %s\n", dir.Name() )
}
fmt.Println("------------------")
fmt.Printf("total: %d blog\n", len(dirs))
},
}delete.go
var deleteCmd = &cobra.Command{
Use: "delete",
Short: "delete a post",
Long: `delete a post`,
Args: func(cmd *cobra.Command, args []string) error {
if len(args) != 1 {
return errors.New("requires a color argument")
}
if strings.Contains(args[0],"/") || strings.Contains(args[0],"..") {
return errors.New("posts name should not contain / or .. ")
}
return nil
},
Run: func(cmd *cobra.Command, args []string) {
fileName := "./posts/" + args[0]
stat, err := os.Stat(fileName)
if os.IsNotExist(err) {
log.Fatalf("post %s is not exist", fileName)
}
if stat.IsDir() {
log.Fatalf("%s is dir ,can not be deleted", fileName)
}
err = os.Remove(fileName)
if err != nil {
log.Fatalf("delete %s fail, err %v", fileName, err)
} else {
log.Printf("delete post %s success", fileName)
}
},
}edit.go 这个有一点麻烦，因为如果调用一个程序比如vim 打开文件，并且golang程序本身要退出，需要detach。暂时放一下（TODO）
我是window测试，linux 更简单一点
PS D:\code\github.com\shalk\blog> go build -o blog.exe . PS D:\code\github.com\shalk\blog> .\blog.exe list ------------------ ------------------ total: 0 blog PS D:\code\github.com\shalk\blog> .\blog.exe new blog1.md 2020/07/26 22:37:15 create file posts/blog1.md PS D:\code\github.com\shalk\blog> .\blog.exe new blog2.md 2020/07/26 22:37:18 create file posts/blog2.md PS D:\code\github.com\shalk\blog> .\blog.exe new blog3.md 2020/07/26 22:37:20 create file posts/blog3.md PS D:\code\github.com\shalk\blog> .\blog list ------------------ blog1.md blog2.md blog3.md ------------------ total: 3 blog PS D:\code\github.com\shalk\blog> .\blog delete blog1.md 2020/07/26 22:37:37 delete post ./posts/blog1.md success PS D:\code\github.com\shalk\blog> .\blog list ------------------ blog2.md blog3.md ------------------ total: 2 blog PS D:\code\github.com\shalk\blog> ls .\posts\ 目录: D:\code\github.com\shalk\blog\posts Mode LastWriteTime Length Name ---- ------------- ------ ---- -a---- 2020/7/26 22:37 0 blog2.md -a---- 2020/7/26 22:37 0 blog3.md PS D:\code\github.com\shalk\blog>
cobra 是一个高效的命令行解析库，利用cobra的脚手架，可以快速的实现一个命令行工具。如果需要更细致的控制，可以参考cobra的官方文档。
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