flag
最后更新于：2022-04-02 02:43:44
[TOC]
## 实例
### 默认带 --help 查询
```
var (
s string
)
func main() {
flag.StringVar(&s,"name", "cc", "input you name")
flag.Parse()
fmt.Printf("%+v\n", s)
}
```
运行
```
> go run main.go --help
-name string
input you name (default "cc")
> go run main.go --name cpj //只能用 --name, -name无效
cpj
```
### 主动打印 help 信息
```
var (
help bool
file string
number int
)
func init() {
flag.BoolVar(&help, "h", false, "this is help")
// `file` 写在最后的注释中,可使 -f string 改为 -f file
flag.StringVar(&file, "f", "", "this is a `file`")
flag.IntVar(&number, "n", 0, "tshi is a `number`")
flag.Usage = usage
}
func main() {
flag.Parse()
if file != "" {
log.Println("file is ", file)
lookup := flag.Lookup("f")
// 打印参数的数据
fmt.Printf("%+v\n", lookup) //&{Name:f Usage:this is a `file` Value:test.file DefValue:}
}
if number != 0 {
log.Println("number is", number)
}
fmt.Println(flag.Args())
if help {
//主动打印信息
flag.Usage()
}
}
func usage() {
fmt.Fprintf(os.Stdout, `test version: test/1.10.0
Usage: test [-hvVtTq] [-s signal] [-c filename] [-p prefix] [-g directives]
Options:
`)
flag.PrintDefaults()
}
```
output
```
Usage: test [-hvVtTq] [-s signal] [-c filename] [-p prefix] [-g directives]
Options:
-f file
this is a file
-h this is help
-n number
tshi is a number
```
';