generated from bing/readnotes
83 lines
2.2 KiB
Markdown
83 lines
2.2 KiB
Markdown
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# cobra
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[cobra](http://github.com/spf13/cobra) 是一个强大开源的go命令行包，很多开源项目都使用cobra实现启动入口，如kubernetes。
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# 安装
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```bash
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go get github.com/spf13/cobra
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```
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# 使用
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使用cobra需要先创建一个`Command`对象，然后执行这个对象的`Execute`方法
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```go
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cmd := cobra.Command{Use: "cobra"}
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cmd.Execute()
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```
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上面的代码没有任何功能,任何参数都不进行处理。
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现在来扩展一下
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```go
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cmd := cobra.Command{
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Use: "cobra",
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Short: "this is a cobra demo",
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Run: func(cmd *cobra.Command, args []string){
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fmt.Println("good! you run a cobra command!")
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},
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}
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cmd.Execute()
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```
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这里为cmd赋值了两个属性`Short` 和`Run`。 `Short` 就是帮助信息的简短说明，`Run` 就是命令行命中时执行的方法。 由于现在只有一个根命令，所以执行的话会打印`good! you run a cobra command!` 添加任何命参数(`-`开头)将会显示错误及usage信息。
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下面为cmd添加一个子命令，并处理参数`-n`
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```go
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cmd := cobra.Command{
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Use: "cobra",
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Short: "this is a cobra demo",
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Run: func(cmd *cobra.Command, args []string){
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fmt.Println("good! you run a cobra command!")
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},
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}
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var newLine *bool
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subCmd := cobra.Command{
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Use: "echo",
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Short: "echo your input",
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Run: func(cmd *cobra.Command, args []string){
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for _, arg := range args {
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if newLine != nil && *newLine{
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fmt.Println(arg)
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}else{
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fmt.Printf("%s ", arg)
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}
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}
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if newLine == nil || ! *newLine{
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fmt.Println()
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}
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},
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}
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newLine = subCmd.Flags().BoolP("newline", "n", false, "display one word per line")
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cmd.AddCommand(&subCmd)
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cmd.Execute()
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```
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这是一个简单的`echo`程序， cmd 拥有一个子命令 `subCmd`, `subCmd`通过`echo`(`Use: "echo"`)调用。`newLine = subCmd.Flags().BoolP("newline", "n", false, "display one word per line")` 为`subCmd` 添加了一个可选布尔型参数`-n`或`--newline`，这个参数的默认值是`false`。`newLine` 记录这个参数的值并在`Run`回调方法中使用。
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运行结果
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```bash
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$ go run cobra.go echo aaa bbb
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aaa bbb
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```
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```bash
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$ go run cobra.go echo -n aaa bbb
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aaa
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bbb
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```
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