How to Add Flags and Arguments to a Go CLI

Use the flag package to define flags and os.Args to access positional arguments. Define flags with flag.String, flag.Int, or flag.Bool, then call flag.Parse() before accessing them.

package main

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

func main() {
	name := flag.String("name", "World", "A name to greet")
	count := flag.Int("count", 1, "Number of greetings")
	flag.Parse()

	args := flag.Args()
	for i := 0; i < *count; i++ {
		fmt.Printf("Hello, %s!\n", *name)
		if len(args) > 0 {
			fmt.Println("Extra arg:", args[0])
		}
	}
}

Run with: go run main.go -name=Go -count=2 extra-text

Flags are named switches like -name=Go that let users change program behavior, while arguments are extra words typed after the command. Think of flags as settings on a remote control and arguments as the specific channel you want to watch. You use flags to configure options and arguments to pass data directly to the program.