我可以添加带有Go标志的命令吗？

Question

I know I can define flags like this:

initPtr := flag.String("init", "config.json", "Initialize with config filename")

Which I will call like this:

myapp --init=myconfig.json

I wonder though if I can define something like commands so that to call the app like this?

myapp init --filename=myconfig.json
myapp check --filename=myconfig.json
myapp run

Answer 1

Yes, you can.

Take a look at https://golang.org/pkg/flag/ for FlagSet documentation.

And for a working example: https://github.com/constabulary/gb/blob/master/cmd/gb/main.go

And an example as requested by miltonb:

% go run flagset.go init --filename=foo.json foo bar
init foo.json [foo bar]
% go run flagset.go check --filename=bar.json 1 2 3
check bar.json [1 2 3]
% go run flagset.go run
run
% cat flagset.go
package main

import (
    "flag"
    "fmt"
    "os"
)

func main() {
    init := flag.NewFlagSet("init", flag.ExitOnError)
    initFile := init.String("filename", "myconfig.json", "configuration file")

    check := flag.NewFlagSet("check", flag.ExitOnError)
    checkFile := check.String("filename", "myconfig.json", "configuration file")

    if len(os.Args) <= 1 {
        flag.Usage()
        os.Exit(1)
    }

    switch os.Args[1] {
    case "init":
        if err := init.Parse(os.Args[2:]); err == nil {
            fmt.Println("init", *initFile, init.Args())
        }
    case "check":
        if err := check.Parse(os.Args[2:]); err == nil {
            fmt.Println("check", *checkFile, check.Args())
        }
    case "run":
        fmt.Println("run")
    }
}