golang命令行参数解析
1. os基础处理os包中有一个string类型的切片变量os.Args，其用来处理一些基本的命令行参数，它在程序启动后读取命令行输入的参数。参数会放置在切片os.Args[]中（以空格分隔），从索引1开始（os.Args[0]放的是程序本身的名字）。 fmt.Println("Parameters:",os.Args[1:])
? 2. flag参数解析flag包可以用来解析命令行选项，但通常被用来替换基本常量。例如，在某些情况下希望在命令行给常量一些不一样的值。 type Flag struct {
Name string // name as it appears on command line
Usage string // help message
Value Value // value as set
DefValue string // default value (as text); for usage message
}
flag的使用规则是：首先定义flag（定义的flag会被解析），然后使用Parse()解析flag，解析后已定义的flag可以直接使用，未定义的剩余的flag可通过Arg(i)单独获取或通过Args()切片整个获取。 定义flag func String(name string,value string,usage string) *string func StringVar(p *string,name string,usage string) func Int(name string,value int,usage string) *int func IntVar(p *int,usage string) 解析flag func Parse() Parse() parses the command-line flags from os.Args[1:]. Must be called after all flags are defined and before flags are accessed by the program. func Arg(i int) string func Args() []string Arg returns the i‘th command-line argument. Arg(0) is the first remaining argument after flags have been processed. Args returns the non-flag command-line arguments. After parsing,the arguments following the flags are available as the slice flag.Args() or individually as flag.Arg(i). The arguments are indexed from 0 through flag.NArg()-1. func NArg() int NArg is the number of arguments remaining after flags have been processed. Flags may then be used directly. If you‘re using the flags themselves,they are all pointers; if you bind to variables,they‘re values. package main
import (
"fmt"
"flag"
)
func main(){
var new_line = flag.Bool("n",false,"new line")
var max_num int
flag.IntVar(&max_num,"MAX_NUM",100,"the num max")
flag.PrintDefaults()
flag.Parse()
fmt.Println("There are",flag.NFlag(),"remaining args,they are:",flag.Args())
fmt.Println("n has value: ",*new_line)
fmt.Println("MAX_NJUM has value: ",max_num)
}
$ go build -o flag flag.go
$ ./flag
-MAX_NUM int
the num max (default 100)
-n new line
There are 0 remaining args,they are: []
n has value: false
MAX_NJUM has value: 100
$ ./flag -n -MAX_NUM=1000 wang qin
-MAX_NUM int
the num max (default 100)
-n new line
There are 2 remaining args,they are: [wang qin]
n has value: true
MAX_NJUM has value: 1000
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