如何在Go CLI程序中输入不带参数的可选标志

Question

I have read the docs for the following two libraries used to create flags. :

1. https://golang.org/pkg/flag/
2. https://github.com/codegangsta/cli

And have not come across a way to do optional flags. How can this be done?

According to the code from https://gobyexample.com/command-line-flags :

package main
import "flag"
import "fmt"

func main() {
  boolPtr := flag.Bool("fork", false, "a bool")
  fmt.Println("fork:", *boolPtr)
}

and executed by : $ ./command-line-flags -fork

Should result in true, this is the behavior I desire but I am getting false on my machine.

Any guidance would be appreciated, Thanks

Answer 1

You must parse the flags after all flags are defined and before flags are accessed:

func main() {
  boolPtr := flag.Bool("fork", false, "a bool")
  flag.Parse()  // add this line
  fmt.Println("fork:", *boolPtr)
}

With this change, the fork flag will work as desire.