命令行支持"/>
golang程序包开发，复杂命令行支持
支持子命令命令行程序支持包开发
任务
- 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
- 将带子命令的命令行处理程序的 import (“github/spf13/cobra”) 改为 import (corbra “gitee/yourId/yourRepo”)
- 使得命令行处理程序修改代价最小，即可正常运行
一、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
查看Cobra包的readme。
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.
可以看到，Cobra包提供了一个简单的接口，使得用户可以创建具有复杂功能的命令行程序。
Getting Started
为了使用Cobra包，先将其下载到本地。
go get -u github/spf13/cobra
然后在需要用到Cobra包的文件中import即可
import "github/spf13/cobra"
参考官方的readme教程，建立一个简易的组织结构如下：
Create rootCmd
在root.go中编写代码如下：
定义了一个根命令，cobra.Command是一个结构体，通过命令来执行Run函数。在此根命令中，通过执行Run函数可以打印一串字符串HAHAHA
package cmdimport ("os""fmt""github/spf13/cobra"
)var rootCmd = &cobra.Command{Use: "hugo",Short: "Hugo is a very fast static site generator",Long: `A Fast and Flexible Static Site Generator built withlove by spf13 and friends in Go.Complete documentation is available at `,Run: func(cmd *cobra.Command, args []string) {// Do Stuff Herefmt.Printf("HAHAHA\n")},
}func Execute() {if err := rootCmd.Execute(); err != nil {fmt.Fprintln(os.Stderr, err)os.Exit(1)}
}Create my main.go
main.go中代码如下，作用是执行根命令
package mainimport ("github/github-user/niceapp/cmd"
)func main() {cmd.Execute()
}
编译并执行niceapp
Create additional commands
为了给根命令加上子命令，创建一个新的文件cmd/version.go
package cmdimport ("fmt""github/spf13/cobra"
)func init() {rootCmd.AddCommand(versionCmd)
}var versionCmd = &cobra.Command{Use: "version",Short: "Print the version number of Hugo",Long: `All software has versions. This is Hugo's`,Run: func(cmd *cobra.Command, args []string) {fmt.Println("Hugo Static Site Generator v0.9 -- HEAD")},
}
重新编译并执行niceapp，在niceapp后加上子命令version
Assign flags to a command
修改root.go，给命令增加标志
rootCmd.PersistentFlags().StringVarP(&author, "author", "a", "YOUR NAME", "Author name for copyright attribution")
此时再次编译执行，即可在niceapp后添加标志a，并且可以传入a后跟着的参数
二、模仿 cobra.Command 编写一个 myCobra 库
任务要求
模仿 cobra 库的 command.go 重写一个 Command.go
- 仅允许使用的第三方库 flag “github/spf13/pflag”
- 可以参考、甚至复制原来的代码
- 必须实现简化版的 type Command struct 定义和方法
- 不一定完全兼容 github/spf13/cobra
- 可支持简单带子命令的命令行程序开发
Create myCobra
新建一个myCobra的包，包内新建一个command.go的文件，查看cobra/command.go的源代码，
发现其首先定义了一个结构体Command，模仿cobra/command.go，定义自己的Command如下：
type Command struct {Use string // Use is the one-line usage message.Short string // Short is the short description shown in the 'help' output.Long string // Long is the long message shown in the 'help <this-command>' outputmands []*Command // commands is the list of commands supported by this program.parent *Command // parent is a parent command for this command.Run func(cmd *Command, args []string) // Run: Typically the actual work function. Most commands will only implement this.args []string // args is actual args parsed from flags.pflags *flag.FlagSet // pflags contains persistent flags.
}
通过步骤一的简单练习，确定编写的Command.go主要包含的功能有：
- 打印帮助信息
- 支持子命令的创建和执行
- 支持命令带选项
有了这个目标，接下来要做的就是去实现它。
一、关键函数
AddCommand
为了支持子命令的创建，无疑要实现AddCommand()函数，AddCommand()可以接收任意个Command类型的参数，当发现接收的子命令与自身相同时，应该返回一条错误信息，即不能将自身作为自身的子命令。否则，将子命令的父命令标志为自身，并将子命令添加。
func (c *Command) AddCommand(cmds ...*Command){for i, x := range cmds {if cmds[i] == c {panic("Command can't be a child of itself")}cmds[i].parent = ccmands = append(cmands, x)}
}
PersistentFlags
获取命令后跟着的选项
func (c *Command) PersistentFlags() *flag.FlagSet {if c.pflags == nil {c.pflags = flag.NewFlagSet(c.Name(), flag.ContinueOnError)}return c.pflags
}
execute
执行命令，若当前命令后跟着子命令，则不执行此命令，转而进入子命令，若当前命令后已经没有子命令，则执行当前命令。值得一提的是，若当前命令后既跟着参数，又带着子命令。则会执行当前命令，
例如：执行
niceapp -a hello version
和
niceapp version
前者会执行根命令，后者会执行version命令。
具体实现思路是，当前命令发现参数中包含自身的子命令时，会执行该子命令的execute()函数，直到当前命令发现自身的参数中不包含有子命令时，才会执行当前命令。通过PersistentFlags().Parse(c.args)来解析命令中的参数。
func (c *Command) execute() (err error) {var e errorif c == nil {return fmt.Errorf("Called Execute() on a nil Command")}if c.args == nil && len(os.Args)>1 && c.parent == nil{c.args = os.Args[1:]}c.PersistentFlags().Parse(c.args)for i, x := range cmands{if len(c.args) == 0 {break}if c.args[0] == "-h" || c.args[0] == "-help"{c.printhelp()return e;}if x.Use == c.args[0]{if len(c.args) > 1{x.args = c.args[1:]}x.execute()break}if i == len(cmands)-1{c.Run(c,c.args)}}if len(c.args) == 0 || len(cmands) == 0{if len(c.args) > 0{if c.args[0] == "-h" || c.args[0] == "-help"{c.printhelp()return e;} }c.Run(c,c.args)}return e
}
printhelp
打印帮助信息，主要是模仿Cobra包中command的帮助信息格式。
func (c *Command) printhelp(){fmt.Println(c.Long)fmt.Println()fmt.Printf("Usage:\n ")var use []stringfor p := c; p != nil; p = p.Parent() {use = append(use, p.Use)}for i:=len(use)-1; i >= 0; i--{fmt.Printf("%s ",use[i])}fmt.Printf("[flags]\n ")if len(cmands) > 0{for i:=len(use)-1; i >= 0; i--{fmt.Printf("%s ",use[i])}fmt.Printf("[command]\n\nAvailable Commands:\n")}if c == c.Root(){fmt.Printf(" help Help about any command\n")}for _,x := range cmands{fmt.Printf(" %-12s%s\n",x.Use,x.Short)}fmt.Printf("\nFlags:\n")c.PersistentFlags().VisitAll(func (flag *flag.Flag) {fmt.Printf(" -%1s, --%-6s %-12s%s (default \"%s\")\n", flag.Shorthand, flag.Name, flag.Value.Type(), flag.Usage, flag.DefValue)})fmt.Printf(" -%1s, --%-19s%s%s\n", "h", "help", "help for ", c.Use)if len(cmands) > 0 {fmt.Printf("\nUse \"%s [command] --help\" for more information about a command.\n",c.Use)}
}
二、功能测试
首先安装包
go install github/github-user/myCobra
然后修改步骤一中root.go和version.go的import文件，改成自己的。
还是先执行相同的命令
修改root.go,使得命令后接参数-a，再次执行
可以看到，和练习一时得到相同的输出，试着在子命令后再加一个子命令
package cmdimport ("fmt"//"github/spf13/cobra"cobra "github/github-user/myCobra"
)func init() {versionCmd.AddCommand(verCmd)
}var versionCmd = &cobra.Command{Use: "version",Short: "Print the version number of Hugo",Long: `All software has versions. This is Hugo's`,Run: func(cmd *cobra.Command, args []string) {fmt.Println("Hugo Static Site Generator v0.9 -- HEAD")},
}var verCmd = &cobra.Command{Use: "ver",Short: "Print the ver",Long: `All software has v`,Run: func(cmd *cobra.Command, args []string) {fmt.Println("helloworld")},
}
得到子命令的输出helloworld。
试着在不同级别的命令下打印帮助信息：
kangze@ubuntu:~/gopath/src/github/github-user/niceapp$ niceapp -h
Usage of hugo:-a, --author string Author name for copyright attribution (default "YOUR NAME")
A Fast and Flexible Static Site Generator built withlove by spf13 and friends in Go.Complete documentation is available at :hugo [flags]hugo [command]Available Commands:help Help about any commandversion Print the version number of Hugover Print the verFlags:-a, --author string Author name for copyright attribution (default "YOUR NAME")-h, --help help for hugoUse "hugo [command] --help" for more information about a command.kangze@ubuntu:~/gopath/src/github/github-user/niceapp$ niceapp version -h
Usage of hugo:-a, --author string Author name for copyright attribution (default "YOUR NAME")
Usage of version:
All software has versions. This is Hugo'sUsage:hugo version [flags]hugo version [command]Available Commands:ver Print the verFlags:-h, --help help for versionUse "version [command] --help" for more information about a command.kangze@ubuntu:~/gopath/src/github/github-user/niceapp$ niceapp version ver -h
Usage of hugo:-a, --author string Author name for copyright attribution (default "YOUR NAME")
Usage of version:
Usage of ver:
All software has vUsage:hugo version ver [flags]Flags:-h, --help help for ver可以看到在不同级别的命令下输出的帮助信息是不同的。
三、单元测试
主要对execute函数和Addcommand函数进行测试
package myCobraimport ("testing""fmt""os/exec"
)var rootCmd = &Command{Use: "hugo",Short: "Hugo is a very fast static site generator",Long: `A Fast and Flexible Static Site Generator built withlove by spf13 and friends in Go.Complete documentation is available at `,Run: func(cmd *Command, args []string) {fmt.Printf("HAHAHA\n")},
}
var versionCmd = &Command{Use: "version",Short: "Print the version number of Hugo",Long: `All software has versions. This is Hugo's`,Run: func(cmd *Command, args []string) {fmt.Println("Hugo Static Site Generator v0.9 -- HEAD")},
}
var author stringfunc TestAddCommand(t *testing.T) {for _, x := range rootCmdmands {if x == versionCmd {t.Errorf("expected: nil got: %v\n",rootCmdmands)}}rootCmd.AddCommand(versionCmd)for _, x := range rootCmdmands {if x == versionCmd {return}}t.Errorf("expected: %v got: %v\n", versionCmd,rootCmdmands)
}func TestExecute(t *testing.T){stdout, err := exec.Command("bash", "-c", "niceapp -a xkz").Output()str := string(stdout)str2 := "xkzHAHAHA"for i:=0;i<len(str2);i++{if str[i] != str2[i]{t.Errorf("expected: %s but got %s\n",str2,str)}}if err != nil {t.Error(err)}stdout, err = exec.Command("bash", "-c", "niceapp version ver").Output()str = string(stdout)str2 = "helloworld"for i:=0;i<len(str2);i++{if str[i] != str2[i]{t.Errorf("expected: %s but got %s\n",str2,str)break}}if err != nil {t.Error(err)}
}
当执行命令得到的输出与期望输出不一致时将会输出错误信息，并且若当增加子命令增加错误时也会输出相应信息。
gitee地址
myCobra
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