Golang: Cobra命令行參數(shù)庫(kù)的使用

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(xiàn)了cobra 可執(zhí)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(zhí)行軟件。

cobra程序只能在GOPATH之下使用，所以首先你需要進(jìn)入到GOPATH的src目錄之下，在該目錄下，輸入:

cobra init demo

在你的當(dāng)前目錄下，應(yīng)該已經(jīng)生成了一個(gè)demo文件夾:

demo
├── cmd
│   └── root.go
├── LICENSE
└── main.go

上述便是該文件夾的結(jié)構(gòu)，我們可以進(jìn)去該文件夾，運(yùn)行:

go run main.go

應(yīng)該會(huì)打印如下結(jié)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(xiàng)目便已經(jīng)生成完畢。

如果你并不想運(yùn)行cobra的可執(zhí)行命令生成示例代碼，只想在項(xiàng)目使用其庫(kù)代碼，則上面的內(nèi)容可以忽略。

附 demo 文件夾的內(nèi)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(shí)際操作其實(shí)cobra都能幫你完成，假設(shè)我們現(xiàn)在需要添加一個(gè)test參數(shù)，在項(xiàng)目文件夾下命令行輸入:

cobra add test

執(zhí)行完成后，現(xiàn)在我們的demo結(jié)構(gòu)應(yīng)該是:

.
├── cmd
│   ├── root.go
│   └── test.go
├── LICENSE
└── main.go

可以看到，在cmd目錄下，已經(jīng)生成了一個(gè)與我們命令同名的go文件，你也許已經(jīng)猜測(cè)到，與該命令有關(guān)的操作也正是在此處實(shí)現(xiàn)。現(xiàn)在執(zhí)行這個(gè)子命令:

go run main.go test

命令行將會(huì)打印輸出test called
那么現(xiàn)在又有一個(gè)問題，如果我們想添加子命令下的子命令呢？
現(xiàn)在讓我們打開test.go,你應(yīng)該看到如下的文件內(nèi)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(huì)發(fā)現(xiàn)，在init中有一句 rootCmd.AddCommand(testCmd) 這個(gè)rootCmd是什么？打開root.go，你會(huì)發(fā)現(xiàn)rootCmd其實(shí)就是我們的根命令。我相信機(jī)智的同學(xué)已經(jīng)猜出來(lái)我們添加子命令的子命令的方法了。現(xiàn)在讓我們?cè)赾md目錄下新建testson.go文件，項(xiàng)目文件結(jié)構(gòu)為：

.
├── cmd
│   ├── root.go
│   └── test.go
│   └── testson.go
├── LICENSE
└── main.go

把test.go的內(nèi)容復(fù)制進(jìn)去，并testson.go文件修改為如下內(nèi)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(xiàn)在在命令行運(yùn)行:

go run main.go test testson

當(dāng)你看到testson called,恭喜你，子命令添加成功！否則你應(yīng)當(dāng)檢查你的代碼是否有誤。

添加參數(shù)

我相信從init函數(shù)中的注釋中，你已經(jīng)得到了足夠多的信息來(lái)自己操作添加flag，但我還是想要啰嗦兩句。首先是persistent參數(shù)，當(dāng)你的參數(shù)作為persistent flag存在時(shí)，如注釋所言，在其所有的子命令之下該參數(shù)都是可見的。而local flag則只能在該命令調(diào)用時(shí)執(zhí)行。可以做一個(gè)簡(jiǎn)單的測(cè)試，在test.go的init函數(shù)中，添加如下內(nèi)容:

testCmd.PersistentFlags().String("foo", "", "A help for foo")
testCmd.Flags().String("foolocal", "", "A help for foo")

現(xiàn)在在命令行 go run main.go test -h 得到如下結(jié)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.

接著讓我們?cè)龠\(yùn)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(fā)現(xiàn)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(lái)你可能會(huì)問，那flag支持什么類型參數(shù)？答案是，請(qǐng)查看官方文檔
請(qǐng)注意，cmd.Flags().String()與 cmd.Flags().StringP()是不一樣的。假如我們?cè)趖est.go的init下增加如下兩行:

testCmd.Flags().String("f", "", "test")
testCmd.Flags().StringP("aaa", "a", "", "test")

前者調(diào)用需要如下形式:

go run main.go test --f

后者有如下兩種形式調(diào)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(shù)，如[]string:

testCmd.Flags().StringSliceP("arr","r", nil, "test arr")

調(diào)用該參數(shù)的方法為:

go run main.go test -r "a,b,c"

請(qǐng)不要鍵入多余空格（除非確實(shí)需要鍵入），也不要使用空格替代逗號(hào)作為分割符。

獲取參數(shù)值

在知道了如何設(shè)置參數(shù)后，我們的下一步當(dāng)然便是需要在運(yùn)行時(shí)獲取該參數(shù)的值。現(xiàn)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(cè)到Use,Short,Long三個(gè)參數(shù)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(yīng)該在Run這里來(lái)獲取參數(shù)并執(zhí)行我們的命令功能。獲取參數(shù)其實(shí)也并不復(fù)雜。以testCmd.Flags().StringP("aaa", "a", "", "test")此為例，我們可以在Run函數(shù)里添加：

str := testCmd.Flags().GetString("aaa")

這樣便可以獲取到該參數(shù)的值了，其余類型參數(shù)獲取也是同理。如 testCmd.Flags().GetStringSlice("arr")，規(guī)律并不難見。

posted @ 2018-04-27 15:03 微信公眾號(hào)--共鳴圈閱讀(10667) 評(píng)論(0) 收藏舉報(bào)

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