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. 我已经阅读了用于创建标志的以下两个库的文档。 : ：

And have not come across a way to do optional flags. 并没有遇到过做可选标志的方法。 How can this be done? 如何才能做到这一点？

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 并执行：$ ./command-line-flags -fork

Should result in true, this is the behavior I desire but I am getting false on my machine. 应该是真的，这是我想要的行为，但我在我的机器上变得虚假。

Any guidance would be appreciated, Thanks 任何指导将不胜感激，谢谢

Answer 1

You must parse the flags after all flags are defined and before flags are accessed: 在定义所有标志之后和访问标志之前，您必须解析标志：

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. 通过此更改， fork标志将按fork工作。