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cobra 是 go 语言的一个库,能够用于编写命令行工具。通常咱们能够看到 git pull
、docker container start
、apt install
等等这样命令,都能够很容易用 corba 来实现,另外,go 语言是很容易编译成一个二进制文件,本文将实现一个简略的命令行工具。
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]:创立一篇新的 blog
blog list:列出以后有哪些文章
blog delete [post-name]: 删除某一篇文章
blog edit [post-name]:编辑某一篇文章
打算有以下几个步骤
- 创立模块
- 用 cobra 的命令行,创立命令行入口
- 用 cobra 的命令行,创立子命令
- 编写性能逻辑
创立模块
$ go mod init github.com/shalk/blog
go: creating new go.mod: module github.com/shalk/blog
创立命令行入口
说到命令行,可能会想到 bash 的 getopt 或者 java 的 jcommand,能够解析各种格调的命令行,然而通常这些命令行都有固定的写法,这个写法个别还记不住要找一个模板参考以下。cobra 除了能够解析命令行之外,还提供了命令行,能够生成模板。先装置这个命令行, 并且把库的依赖加到 go.mod 里
$ go get -u github.com/spf13/cobra/cobra
cobra 会装置到 $GOPATH\bin
目录下,留神环境变量中把它退出 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
目录构造如下:
./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.
命令行就创立好了,看上去一行代码也不必写,因为随着理解的深刻,前面须要调整生成的代码,还是要理解一下 cobra 代码的套路。
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(这里比拟非凡),-u 就是 flag,test.com/a/b 就是 args
那么命令行就是有三局部形成,所以须要定义好这个
- 命令本身的一些根本信息,用 command 示意,具体对象是 cobra.Command
- 命令的一些标致或者选项,用 flag 示意,具体对象是 flag.FlagSet
- 最初的参数,用 args 示意,通常是 []string
还有一个概念是子命令,比方 get 就是 go 的子命令,这是一个树状构造的关系。
我能够应用 go 命令,也能够应用 go get 命令
例如: root.go,定义了 root 命令,另外在 init 外面 定义了 flag,如果它自身有具体执行,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")
}
如果须要子命令,就须要在 init 里,给 rootCmd.AddCommand() 其余的 command,其余的子命令通常也会独自用一个文件编写,并且有一个全局变量,让 rootCmd 能够 add 它
创立子命令
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 目录下减少了 new.go, delete.go,list.go,edit.go
减少性能代码
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方 vim 关上文件,并且 golang 程序自身要退出,须要 detach。临时放一下(TODO)
编译测试
我是 window 测试,linux 更简略一点
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>
小结
cobra 是一个高效的命令行解析库,利用 cobra 的脚手架,能够疾速的实现一个命令行工具。如果须要更粗疏的管制,能够参考 cobra 的官网文档。