簡介
Cobra既是一個用來創建強大的現代CLI命令行的golang庫,也是一個生成程序應用和命令行文件的程序。下面是Cobra使用的一個演示:
Cobra提供的功能
如何使用
上面所有列出的功能我沒有一一去使用,下面我來簡單介紹一下如何使用Cobra,基本能夠滿足一般命令行程序的需求,如果需要更多功能,可以研究一下源碼github。
安裝cobra
Cobra是非常容易使用的,使用go get來安裝最新版本的庫。當然這個庫還是相對比較大的,可能需要安裝它可能需要相當長的時間,這取決于你的速網。安裝完成后,打開GOPATH目錄,bin目錄下應該有已經編譯好的cobra.exe程序,當然你也可以使用源代碼自己生成一個最新的cobra程序。
> go get -v github.com/spf13/cobra/cobra
使用cobra生成應用程序
假設現在我們要開發一個基于CLIs的命令程序,名字為demo。首先打開CMD,切換到GOPATH的src目錄下[^1],執行如下指令:
[^1]:cobra.exe只能在GOPATH目錄下執行
src> ../bin/cobra.exe init demo Your Cobra application is ready atC:/Users/liubo5/Desktop/transcoding_tool/src/demoGive it a try by going there and running `go run main.go`Add commands to it by running `cobra add [cmdname]`
在src目錄下會生成一個demo的文件夾,如下:
? demo
? cmd/
root.go
main.go
如果你的demo程序沒有subcommands,那么cobra生成應用程序的操作就結束了。
如何實現沒有子命令的CLIs程序
接下來就是可以繼續demo的功能設計了。例如我在demo下面新建一個包,名稱為imp。如下:
? demo
? cmd/
root.go
? imp/
imp.go
imp_test.go
main.go
imp.go文件的代碼如下:
package impimport( "fmt")func Show(name string, age int) { fmt.Printf("My Name is %s, My age is %d/n", name, age)}
demo程序成命令行接收兩個參數name和age,然后打印出來。打開cobra自動生成的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 mainimport "demo/cmd"func main() { cmd.Execute()}
可以看出main函數執行cmd包,所以我們只需要在cmd包內調用imp包就能實現demo程序的需求。接著打開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 cmdimport ( "fmt" "os" "github.com/spf13/cobra" "github.com/spf13/viper")var cfgFile string// RootCmd represents the base command when called without any subcommandsvar RootCmd = &cobra.Command{ Use: "demo", Short: "A brief description of your application", Long: `A longer description that spans multiple lines and likely containsexamples 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 filesto 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()) }}
從源代碼來看cmd包進行了一些初始化操作并提供了Execute接口。十分簡單,其中viper是cobra集成的配置文件讀取的庫,這里不需要使用,我們可以注釋掉(不注釋可能生成的應用程序很大約10M,這里沒喲用到最好是注釋掉)。cobra的所有命令都是通過cobra.Command這個結構體實現的。為了實現demo功能,顯然我們需要修改RootCmd。修改后的代碼如下:
// 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 cmdimport ( "fmt" "os" "github.com/spf13/cobra" // "github.com/spf13/viper" "demo/imp")//var cfgFile stringvar name stringvar age int// RootCmd represents the base command when called without any subcommandsvar 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的功能已經實現了,我們編譯運行一下看看實際效果:
>demo.exe
Demo is a test appcation for print thingsUsage:
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
如何實現帶有子命令的CLIs程序
在執行cobra.exe init demo之后,繼續使用cobra為demo添加子命令test:
src/demo>../../bin/cobra add testtest created at C:/Users/liubo5/Desktop/transcoding_tool/src/demo/cmd/test.go
在src目錄下demo的文件夾下生成了一個cmd/test.go文件,如下:
? demo
? cmd/
root.go
test.go
main.go
接下來的操作就和上面修改root.go文件一樣去配置test子命令。效果如下:
src/demo>demoDemo is a test appcation for print thingsUsage: demo [flags] demo [command]Available Commands: test A brief description of your commandFlags: -a, --age int person's age -h, --help help for demo -n, --name string person's nameUse "demo [command] --help" for more information about a command.
可以看出demo既支持直接使用標記flag,又能使用子命令
src/demo>demo test -hA longer description that spans multiple lines and likely contains examplesand 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 filesto quickly create a Cobra application.Usage: demo test [flags]
調用test命令輸出信息,這里沒有對默認信息進行修改。
src/demo>demo tstError: unknown command "tst" for "demo"Did you mean this? testRun 'demo --help' for usage.unknown command "tst" for "demo"Did you mean this? test
這是錯誤命令提示功能
OVER
Cobra的使用就介紹到這里,更新細節可去github詳細研究一下。這里只是一個簡單的使用入門介紹,如果有錯誤之處,敬請指出,謝謝~
總結
以上就是這篇文章的全部內容了,希望本文的內容對大家的學習或者工作具有一定的參考學習價值,如果有疑問大家可以留言交流,謝謝大家對VEVB武林網的支持。
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