golang标志在第一个非选项后停止解析

Question

i am building a little cli tool that boots my app in development or production.

the way i want it to work is like this:

app run --dev or app run --prod

Atm it doest parses the flags after my command but only before my command. So this works

app --dev run or app --prod run

Any idee how to fix it this so i can use it after my command? here is my code

func main() {
    //flag.Usage := usage
    flag.Parse()
    args := flag.Args()
    if len(args) == 0 {
        Usage()
        os.Exit(0)
    }

    if *dev {
        os.Setenv("ENV", "development")
    }

    if *prod {
        os.Setenv("ENV", "production")
    }

    switch {
    // Run
    case args[0] == "run" && len(args) == 1:
        os.Setenv("port", *port)
        log.Printf("Booting in %s", os.Getenv("ENV"))
        Run()

    // Help
    case args[0] == "help" && len(args) == 1:
        Usage()
    }
}

Answer 1

Traditionally, the UNIX option parser getopt() stops parsing after the first non-option. The glibc altered this behavior to support options in arbitrary positions, a controversial decision. The flag package implements the traditional behavior.

One thing you could do is permuting the arguments array before parsing the flags. That's what the glibc does:

func permutateArgs(args []string) int {
    args = args[1:]
    optind := 0

    for i := range args {
        if args[i][0] == '-' {
            tmp := args[i]
            args[i] = args[optind]
            args[optind] = tmp
            optind++
        }
    }

    return optind + 1
}

This code permutates args such that options are in front, leaving the program name untouched. permutateArgs returns the index of the first non-option after permutation. Use this code like this:

optind := permutateArgs(os.Args)
flags.Parse()

// process non-options
for i := range os.Args[optind:] {
    // ...
}