將cobra下載到 $GOPATH，用命令：
go get -v github.com/spf13/cobra/cobra
然后使用 go install github.com/spf13/cobra/cobra, 安裝后在 $GOBIN 下出現了cobra 可執行程序。如果你沒有配置 $GOBIN，那么可以在$GOPATH/bin 下找到 cobra的可執行軟件。
cobra程序只能在GOPATH之下使用，所以首先你需要進入到GOPATH的src目錄之下，在該目錄下，輸入:
cobra init demo
在你的當前目錄下，應該已經生成了一個demo文件夾:
demo
├── cmd
│ └── root.go
├── LICENSE
└── main.go
上述便是該文件夾的結構，我們可以進去該文件夾，運行:
go run main.go
應該會打印如下結果:
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.至此，我們的cobra項目便已經生成完畢。
如果你並不想運行cobra的可執行命令生成示例代碼，只想在項目使用其庫代碼，則上面的內容可以忽略。
附 demo 文件夾的內容：
cmd/root.go:
// Copyright © 2018 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" homedir "github.com/mitchellh/go-homedir" "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 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/.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 != "" { // Use config file from the flag. viper.SetConfigFile(cfgFile) } else { // Find home directory. home, err := homedir.Dir() if err != nil { fmt.Println(err) os.Exit(1) } // Search config in home directory with name ".demo" (without extension). viper.AddConfigPath(home) viper.SetConfigName(".demo") } 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()) } }
main.go:
// Copyright © 2018 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() }
添加子命令
實際操作其實cobra都能幫你完成，假設我們現在需要添加一個test參數，在項目文件夾下命令行輸入:
cobra add test
執行完成后，現在我們的demo結構應該是:
.
├── cmd
│ ├── root.go
│ └── test.go
├── LICENSE
└── main.go
可以看到，在cmd目錄下，已經生成了一個與我們命令同名的go文件，你也許已經猜測到，與該命令有關的操作也正是在此處實現。現在執行這個子命令:
go run main.go test
命令行將會打印輸出test called
那么現在又有一個問題，如果我們想添加子命令下的子命令呢？
現在讓我們打開test.go,你應該看到如下的文件內容:
// Copyright © 2017 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" "github.com/spf13/cobra" ) // testCmd represents the test command var testCmd = &cobra.Command{ Use: "test", Short: "A brief description of your command", Long: `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.`, Run: func(cmd *cobra.Command, args []string) { fmt.Println("test called") }, } func init() { rootCmd.AddCommand(testCmd) // Here you will define your flags and configuration settings. // Cobra supports Persistent Flags which will work for this command // and all subcommands, e.g.: // testCmd.PersistentFlags().String("foo", "", "A help for foo") // Cobra supports local flags which will only run when this command // is called directly, e.g.: // testCmd.Flags().BoolP("toggle", "t", false, "Help message for toggle") }
你會發現，在init中有一句 rootCmd.AddCommand(testCmd) 這個rootCmd是什么？打開root.go，你會發現rootCmd其實就是我們的根命令。我相信機智的同學已經猜出來我們添加子命令的子命令的方法了。現在讓我們在cmd目錄下新建testson.go文件，項目文件結構為：
.
├── cmd
│ ├── root.go
│ └── test.go
│ └── testson.go
├── LICENSE
└── main.go
把test.go的內容復制進去，並testson.go文件修改為如下內容:
cmd/testson.go:
// Copyright © 2017 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" "github.com/spf13/cobra" ) // testCmd represents the test command var testsonCmd = &cobra.Command{ Use: "testson", Short: "A brief description of your command", Long: `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.`, Run: func(cmd *cobra.Command, args []string) { fmt.Println("testson called") }, } func init() { testCmd.AddCommand(testsonCmd) // Here you will define your flags and configuration settings. // Cobra supports Persistent Flags which will work for this command // and all subcommands, e.g.: // testCmd.PersistentFlags().String("foo", "", "A help for foo") // Cobra supports local flags which will only run when this command // is called directly, e.g.: // testCmd.Flags().BoolP("toggle", "t", false, "Help message for toggle") }
現在在命令行運行:
go run main.go test testson
當你看到testson called,恭喜你，子命令添加成功！否則你應當檢查你的代碼是否有誤。
添加參數
我相信從init函數中的注釋中，你已經得到了足夠多的信息來自己操作添加flag，但我還是想要啰嗦兩句。首先是persistent參數，當你的參數作為persistent flag存在時，如注釋所言，在其所有的子命令之下該參數都是可見的。而local flag則只能在該命令調用時執行。可以做一個簡單的測試，在test.go的init函數中，添加如下內容:
testCmd.PersistentFlags().String("foo", "", "A help for foo") testCmd.Flags().String("foolocal", "", "A help for foo")
現在在命令行 go run main.go test -h 得到如下結果:
$ go run main.go 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] demo test [command] Available Commands: testson A brief description of your command Flags: --foo string A help for foo --foolocal string A help for foo -h, --help help for test Global Flags: --config string config file (default is $HOME/.demo.yaml) Use "demo test [command] --help" for more information about a command.
接着讓我們再運行 go run main.go test testson -h
$ go run main.go test testson -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 testson [flags] Flags: -h, --help help for testson Global Flags: --config string config file (default is $HOME/.demo.yaml) --foo string A help for foo
可以發現在Gloabal Flags的變化。test作為root的子命令，仍然可以使用root的persistent flag-> config（可以查看root.go），而testson作為test的子命令，不僅可以使用test的persistent flag-> fool, 也可以使用test父命令的persistent flag。從而我們可以直觀的看出persistent的作用范圍是該命令之后的所有子命令。接下來你可能會問，那flag支持什么類型參數？答案是，請查看官方文檔
請注意，cmd.Flags().String()與 cmd.Flags().StringP()是不一樣的。假如我們在test.go的init下增加如下兩行:
testCmd.Flags().String("f", "", "test") testCmd.Flags().StringP("aaa", "a", "", "test")
前者調用需要如下形式:
go run main.go test --f
后者有如下兩種形式調用:
go run main.go test --aaa
go run main.go test -a
另外可以額外告知你如何使用slice作為參數，如[]string:
testCmd.Flags().StringSliceP("arr","r", nil, "test arr")
調用該參數的方法為:
go run main.go test -r "a,b,c"
請不要鍵入多余空格（除非確實需要鍵入），也不要使用空格替代逗號作為分割符。
獲取參數值
在知道了如何設置參數后，我們的下一步當然便是需要在運行時獲取該參數的值。現在讓我們把注意力放到test.go的此部分：
var testCmd = &cobra.Command{ Use: "test", Short: "A brief description of your command", Long: `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.`, Run: func(cmd *cobra.Command, args []string) { fmt.Println("test called") }, }
讓我們把注意力重新放到上面的代碼上。我們也很容易可以猜測到Use,Short,Long三個參數的作用，這里便不做闡述（你可以參照添加子命令的子命令的部分的輸出）。顯而易見，我們應該在Run這里來獲取參數並執行我們的命令功能。獲取參數其實也並不復雜。以testCmd.Flags().StringP("aaa", "a", "", "test")此為例，我們可以在Run函數里添加：
str := testCmd.Flags().GetString("aaa")
這樣便可以獲取到該參數的值了，其余類型參數獲取也是同理。如 testCmd.Flags().GetStringSlice("arr")，規律並不難見。