go解析命令行参数方法

golang

1、通过os.Args来获取

var help = func () {
    fmt.Println("Usage for calc tool.")
    fmt.Println("====================================================")
    fmt.Println("add 1 2, return 3")
    fmt.Println("sub 1 2, return -1")
    fmt.Println("mul 1 2, return 2")
    fmt.Println("sqrt 2, return 1.4142135623730951")
}
func CalcByOs() error {
    args := os.Args
    if len(args) < 3 || args == nil {
        help()
        return nil
    }
    operate := args[1]
    switch operate {
    case "add":{
            rt := 0
            number_one, err1 := strconv.Atoi(args[2])
            number_two, err2 := strconv.Atoi(args[3])
            if err1 == nil && err2 == nil {
                rt = number_one + number_two
                fmt.Println("Result ", rt)
            }
        }
    case "sub":
        {
            rt := 0
            number_one, err1 := strconv.Atoi(args[2])
            number_two, err2 := strconv.Atoi(args[3])
            if err1 == nil && err2 == nil {
                rt += number_one - number_two
                fmt.Println("Result ", rt)
            }
        }
    case "mul":
        {
            rt := 1
            number_one, err1 := strconv.Atoi(args[2])
            number_two, err2 := strconv.Atoi(args[3])
            if err1 == nil && err2 == nil {
                rt = number_one * number_two
                fmt.Println("Result ", rt)
            }
        }
    case "sqrt":
        {
            rt := float64(0)
            if len(args) != 3 {
                fmt.Println("Usage: sqrt 2, return 1.4142135623730951")
                return nil
            }
            number_one, err := strconv.ParseFloat(args[2], 64)
            if err == nil {
                rt = math.Sqrt(number_one)
                fmt.Println("Result ", rt)
            }
        }
    default:
        help()
    }
    return nil
}

编译后执行

./calc add 1 2
Result 3
====================
./calc sub 1 2
Result -1
====================
./calc mul 10 20
Result 200
===================
./calc sqrt 2
Result 1.4142135623730951

2、使用flag

flag 包比 os 读取参数更方便。可以自定义传入的参数的类型：比如字符串，整型，浮点型，默认参数设置等
基本用法

var operate string
flag.StringVar(&operate,"o", "add", "operation for calc")
# 解释
绑定 operate 变量， name="o", value="add" , usage="operation for calc"
也可以这样定义为指针变量
var operate := flag.String("o", "add", "operation for calc")
同时还可以自定义 flag 类型
所有变量注册之后，调用 flag.Parse() 来解析命令行参数， 如果是绑定变量的方式，直接使用变量进行操作，
如果使用指针变量型，需要 *operate 这样使用。
flag.Args() 表示接收的所有命令行参数集， 也是一个切片
for index, value := range flag.Args {
  fmt.Println(index, value)
}

示例程序

func CalcByFlag() error {
    var operation string
    var numberone float64
    var numbertwo float64
    flag.StringVar(&operation, "o", "add", "operation for this tool")
    flag.Float64Var(&numberone, "n1", 0, "The first number")
    flag.Float64Var(&numbertwo, "n2", 0, "The second number")
    flag.Parse()
    fmt.Println(numberone, numbertwo)
    if operation == "add" {
        rt := numberone + numbertwo
        fmt.Println("Result ", rt)
    } else if operation == "sub" {
        rt := numberone - numbertwo
        fmt.Println("Result ", rt)
    } else if operation == "mul" {
        rt := numberone * numbertwo
        fmt.Println("Result ", rt)
    } else if operation == "sqrt" {
        rt := math.Sqrt(numberone)
        fmt.Println("Result ", rt)
    } else {
        help()
    }
    return nil
}
最后的结果效果如下：
./calc -o add -n1 1 -n2 2
Result 3
=============================
./calc -o sub -n1 2 -n2 3
Result -1
============================
./calc -o mul -n1 10 -n2 20
Result 200
===========================
./calc -o sqrt -n1 2
Result 1.4142135623730951

3、还是使用flag

const (
    usage = `
    add --one ONE  --two TWO "加法"
`
    add        = "add"
)
func main() {
    addCmd := flag.NewFlagSet(add, flag.ExitOnError)
    one := addCmd.Float64("one", 0, "one")
    two := addCmd.Float64("two", 0, "two")
    switch os.Args[1] {
    case add:
        err := addCmd.Parse(os.Args[2:])
        if err == nil{
            fmt.Println(err)
        }
        if addCmd.Parsed() {
            rt := *one + *two
            fmt.Println("Result ", rt)
        }
    }
}
运行
go run main2.go add --one 123 --two 321