go - Go中的Flags解释

Question

谁能解释一下 Go 中的标志？

flag.Parse()
var omitNewline = flag.Bool("n", false, "don't print final newline")

Answer 1

flags是为命令行程序指定选项的常用方法。

package main

import (
  "flag"
  "fmt"
)

var (
  env *string
  port *int
)

// Basic flag declarations are available for string, integer, and boolean options.
func init() {
  env = flag.String("env", "development", "a string")
  port = flag.Int("port", 3000, "an int")
}

func main() {

  // Once all flags are declared, call flag.Parse() to execute the command-line parsing.
  flag.Parse()

  // Here we’ll just dump out the parsed options and any trailing positional 
  // arguments. Note that we need to dereference the points with e.g. *evn to 
  // get the actual option values.
  fmt.Println("env:", *env)
  fmt.Println("port:", *port)

}

运行程序:

go run main.go

先给它一个不带标志的程序来尝试运行程序。请注意，如果您省略标志，它们会自动采用默认值。

go run command-line-flags.go --env production --port 2000

如果您提供具有指定值的标志，则默认值将被传递的值覆盖。