了解 Cobra包，使用 cobra 命令行生成一个简单的带子命令的命令行程序。模仿 cobra.Command 编写一个 myCobra 库。

了解 Cobra包，使用 cobra 命令行生成一个简单的带子命令的命令行程序。

首先了解一下cobra的作用

Cobra is a library providing a simple interface to create powerful modern CLI interfaces similar to git & go tools.

Cobra is also an application that will generate your application scaffolding to rapidly develop a Cobra-based application.

参考官方文档https://github.com/spf13/cob ra/blob/master/cobra/README.md

准备工作

安装cobra执行文件（值得一提，不能直接在apt上面下载。并不能使用，没有--pkg-name 参数）

由于墙的原因，官网上的cobra 文件不能下载，产生报错

解决：先执行下列代码

参考了https://blog.csdn.net/u013256816/article/details/99619335，表示感谢

再安装cobra

这样还是不能用，所以我执行了

sudo apt install cobra

就可以使用了

但是，注意不可以直接install cobra。不然执行go run main.go时会发生报错。找不到xxx/cmd文件。

步骤1：

先在创建文件夹cobraPractice

命令 makedir cobraPractice

步骤二

初始化

步骤三

创建命令行执行文件

步骤四

简单运行程序

接下来实现自己的简单的cobra

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package myCobra
 
import (
    "fmt"
    "os"
    flag "github.com/spf13/pflag"
    "strings"
)
 
var (
 
)
 
//command struct have all information about a comand
type Command struct {
    Use string
 
    Short string
    Long string 
    Run func(cmd *Command, args []string)
 
    commands []*Command
    choose *Command // sub command at run time
 
    parent *Command
 
    args []string
 
    pflags *flag.FlagSet
 
 
}
 
//add new subCommand to rootCommand 
func (c *Command) AddCommand(sub *Command) {
    for _, v := range c.commands {
        if v == sub {
            return
        }
    }
    c.commands = append(c.commands, sub)
    sub.parent = c
}
 
 
//before execute a command 
func (c *Command) Execute() error {
    if  c == nil {
        return fmt.Errorf("Called Execute() on a nil Command")
    }
    if  c .parent == nil { // root Command
        ParseArgs(c, os.Args[1:])
    }
    c.execute()
    return nil
     
}
 
//execute a command or execute its subCommand
func (c *Command) execute() {
    if c.choose == nil {
         
        c.Run(c, c.args)
        return
    }
    c.choose.execute()
}
 
//retrieve and store all the args for every command
func ParseArgs(c *Command, args []string) {
    //fmt.Printf("%v", args)
    if len(args) < 1 {
        return
    }
    for _, v := range c.commands {
        if v.Use == args[0] { //there is any sub command fit
            c.args = args[:1]
            c.choose = v
            ParseArgs(v, args[1:])
            return
        }
    }
    c.args = args // there is no sub command, then all args belong to current command
    c.PersistentFlags().Parse(c.args)
}
 
 
func (c *Command) PersistentFlags() *flag.FlagSet {
    if c.pflags == nil {
        c.pflags = flag.NewFlagSet(c.Name(), flag.ContinueOnError)
    }
    return c.pflags
}
 
// Name returns the command's name: the first word in the use line.
func (c *Command) Name() string {
    name := c.Use
    i := strings.Index(name, " ")
    if i >= 0 {
        name = name[:i]
    }
    return name
}

代码解析：

此实现比较简单，例如go run main.go printTxt hello中

root是printTxt的父命令、printTxt是hello的父命令，而且此命令只会执行hello.go

如果有参数的话，也是只能由hello(即没有子命令的命令，拥有参数)

func (c *Command) PersistentFlags() *flag.FlagSet {
    if c.pflags == nil {
        c.pflags = flag.NewFlagSet(c.Name(), flag.ContinueOnError)
    }
    return c.pflags
}
 
// Name returns the command's name: the first word in the use line.
func (c *Command) Name() string {
    name := c.Use
    i := strings.Index(name, " ")
    if i >= 0 {
        name = name[:i]
    }
    return name
}

上面的函数，就是给命令加上pflag解析参数的功能

功能使用：

例如

package cmd
 
import (
    "fmt"
 
    //"github.com/spf13/cobra"
    cobra "github.com/wood666/myCobra"
)
var help bool
// printTxtCmd represents the printTxt command
var printTxtCmd = &cobra.Command{
    Use:   "printTxt",
    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) {
        if (help) {
            fmt.Printf("sorry, We can't give you any help, this is a fake CLI\n")
        }
    },
}
 
func init() {
    help = true;
    rootCmd.AddCommand(printTxtCmd)
    printTxtCmd.PersistentFlags().BoolVarP(&help, "h", "h", false, "maybe it can give you some help!!!")
}