golang中命令行库cobra的使用方法示例
简介
Cobra既是一个用来创建强大的现代CLI命令行的golang库,也是一个生成程序应用和命令行文件的程序。下面是Cobra使用的一个演示:
Cobra提供的功能
- 简易的子命令行模式,如 app server, app fetch等等
- 完全兼容posix命令行模式
- 嵌套子命令subcommand
- 支持全局,局部,串联flags
- 使用Cobra很容易的生成应用程序和命令,使用cobra create appname和cobra add cmdname
- 如果命令输入错误,将提供智能建议,如 app srver,将提示srver没有,是否是app server
- 自动生成commands和flags的帮助信息
- 自动生成详细的help信息,如app help
- 自动识别-h,--help帮助flag
- 自动生成应用程序在bash下命令自动完成功能
- 自动生成应用程序的man手册
- 命令行别名
- 自定义help和usage信息
- 可选的紧密集成的viper apps
如何使用
上面所有列出的功能我没有一一去使用,下面我来简单介绍一下如何使用Cobra,基本能够满足一般命令行程序的需求,如果需要更多功能,可以研究一下源码github。
安装cobra
Cobra是非常容易使用的,使用go get来安装最新版本的库。当然这个库还是相对比较大的,可能需要安装它可能需要相当长的时间,这取决于你的速网。安装完成后,打开GOPATH目录,bin目录下应该有已经编译好的cobra.exe程序,当然你也可以使用源代码自己生成一个最新的cobra程序。
> go get -v github.com/spf13/cobra/cobra
使用cobra生成应用程序
假设现在我们要开发一个基于CLIs的命令程序,名字为demo。首先打开CMD,切换到GOPATH的src目录下[^1],执行如下指令:
[^1]:cobra.exe只能在GOPATH目录下执行
src> ..\bin\cobra.exe init demo Your Cobra application is ready at C:\Users\liubo5\Desktop\transcoding_tool\src\demo Give it a try by going there and running `go run main.go` Add commands to it by running `cobra add [cmdname]`
在src目录下会生成一个demo的文件夹,如下:
▾ demo
▾ cmd/
root.go
main.go
如果你的demo程序没有subcommands,那么cobra生成应用程序的操作就结束了。
如何实现没有子命令的CLIs程序
接下来就是可以继续demo的功能设计了。例如我在demo下面新建一个包,名称为imp。如下:
▾ demo
▾ cmd/
root.go
▾ imp/
imp.go
imp_test.go
main.go
imp.go文件的代码如下:
package imp import( "fmt" ) func Show(name string, age int) { fmt.Printf("My Name is %s, My age is %d\n", name, age) }
demo程序成命令行接收两个参数name和age,然后打印出来。打开cobra自动生成的main.go文件查看:
// Copyright © 2016 NAME HERE <EMAIL ADDRESS> // // Licensed under the Apache License, Version 2.0 (the "License"); // you may not use this file except in compliance with the License. // You may obtain a copy of the License at // // http://www.apache.org/licenses/LICENSE-2.0 // // Unless required by applicable law or agreed to in writing, software // distributed under the License is distributed on an "AS IS" BASIS, // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. // See the License for the specific language governing permissions and // limitations under the License. package main import "demo/cmd" func main() { cmd.Execute() }
可以看出main函数执行cmd包,所以我们只需要在cmd包内调用imp包就能实现demo程序的需求。接着打开root.go文件查看:
// Copyright © 2016 NAME HERE <EMAIL ADDRESS> // // Licensed under the Apache License, Version 2.0 (the "License"); // you may not use this file except in compliance with the License. // You may obtain a copy of the License at // // http://www.apache.org/licenses/LICENSE-2.0 // // Unless required by applicable law or agreed to in writing, software // distributed under the License is distributed on an "AS IS" BASIS, // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. // See the License for the specific language governing permissions and // limitations under the License. package cmd import ( "fmt" "os" "github.com/spf13/cobra" "github.com/spf13/viper" ) var cfgFile string // RootCmd represents the base command when called without any subcommands var RootCmd = &cobra.Command{ Use: "demo", 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 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 $HOME/.demo.yaml)") // Cobra also supports local flags, which will only run // when this action is called directly. RootCmd.Flags().BoolP("toggle", "t", false, "Help message for toggle") } // initConfig reads in config file and ENV variables if set. func initConfig() { if cfgFile != "" { // enable ability to specify config file via flag viper.SetConfigFile(cfgFile) } viper.SetConfigName(".demo") // name of config file (without extension) viper.AddConfigPath("$HOME") // adding home directory as first search path viper.AutomaticEnv() // read in environment variables that match // If a config file is found, read it in. if err := viper.ReadInConfig(); err == nil { fmt.Println("Using config file:", viper.ConfigFileUsed()) } }
从源代码来看cmd包进行了一些初始化操作并提供了Execute接口。十分简单,其中viper是cobra集成的配置文件读取的库,这里不需要使用,我们可以注释掉(不注释可能生成的应用程序很大约10M,这里没哟用到最好是注释掉)。cobra的所有命令都是通过cobra.Command这个结构体实现的。为了实现demo功能,显然我们需要修改RootCmd。修改后的代码如下:
// Copyright © 2016 NAME HERE <EMAIL ADDRESS> // // Licensed under the Apache License, Version 2.0 (the "License"); // you may not use this file except in compliance with the License. // You may obtain a copy of the License at // // http://www.apache.org/licenses/LICENSE-2.0 // // Unless required by applicable law or agreed to in writing, software // distributed under the License is distributed on an "AS IS" BASIS, // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. // See the License for the specific language governing permissions and // limitations under the License. package cmd import ( "fmt" "os" "github.com/spf13/cobra" // "github.com/spf13/viper" "demo/imp" ) //var cfgFile string var name string var age int // RootCmd represents the base command when called without any subcommands var RootCmd = &cobra.Command{ Use: "demo", Short: "A test demo", Long: `Demo is a test appcation for print things`, // Uncomment the following line if your bare application // has an action associated with it: Run: func(cmd *cobra.Command, args []string) { if len(name) == 0 { cmd.Help() return } imp.Show(name, age) }, } // Execute adds all child commands to the root command 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 $HOME/.demo.yaml)") // Cobra also supports local flags, which will only run // when this action is called directly. // RootCmd.Flags().BoolP("toggle", "t", false, "Help message for toggle") RootCmd.Flags().StringVarP(&name, "name", "n", "", "person's name") RootCmd.Flags().IntVarP(&age, "age", "a", 0, "person's age") } // initConfig reads in config file and ENV variables if set. //func initConfig() { // if cfgFile != "" { // enable ability to specify config file via flag // viper.SetConfigFile(cfgFile) // } // viper.SetConfigName(".demo") // name of config file (without extension) // viper.AddConfigPath("$HOME") // adding home directory as first search path // viper.AutomaticEnv() // read in environment variables that match // // If a config file is found, read it in. // if err := viper.ReadInConfig(); err == nil { // fmt.Println("Using config file:", viper.ConfigFileUsed()) // } //}
到此demo的功能已经实现了,我们编译运行一下看看实际效果:
>demo.exe
Demo is a test appcation for print things
Usage:
demo [flags]
Flags:
-a, --age int person's age
-h, --help help for demo
-n, --name string person's name
>demo -n borey --age 26
My Name is borey, My age is 26
如何实现带有子命令的CLIs程序
在执行cobra.exe init demo之后,继续使用cobra为demo添加子命令test:
src\demo>..\..\bin\cobra add test test created at C:\Users\liubo5\Desktop\transcoding_tool\src\demo\cmd\test.go
在src目录下demo的文件夹下生成了一个cmd\test.go文件,如下:
▾ demo
▾ cmd/
root.go
test.go
main.go
接下来的操作就和上面修改root.go文件一样去配置test子命令。效果如下:
src\demo>demo Demo is a test appcation for print things Usage: demo [flags] demo [command] Available Commands: test A brief description of your command Flags: -a, --age int person's age -h, --help help for demo -n, --name string person's name Use "demo [command] --help" for more information about a command.
可以看出demo既支持直接使用标记flag,又能使用子命令
src\demo>demo test -h A longer description that spans multiple lines and likely contains examples and usage of using your command. 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. Usage: demo test [flags]
调用test命令输出信息,这里没有对默认信息进行修改。
src\demo>demo tst Error: unknown command "tst" for "demo" Did you mean this? test Run 'demo --help' for usage. unknown command "tst" for "demo" Did you mean this? test
这是错误命令提示功能
OVER
Cobra的使用就介绍到这里,更新细节可去github详细研究一下。这里只是一个简单的使用入门介绍,如果有错误之处,敬请指出,谢谢~
总结