log
最后更新于：2022-04-02 02:44:26
[TOC]
## log
语法
```
type Logger
func New(out io.Writer, prefix string, flag int) *Logger
func (l *Logger) Flags() int
func (l *Logger) SetFlags(flag int)
func (l *Logger) Prefix() string
func (l *Logger) SetPrefix(prefix string)
func (l *Logger) Output(calldepth int, s string) error
func (l *Logger) Printf(format string, v ...interface{})
func (l *Logger) Print(v ...interface{})
func (l *Logger) Println(v ...interface{})
func (l *Logger) Fatalf(format string, v ...interface{})
func (l *Logger) Fatal(v ...interface{})
func (l *Logger) Fatalln(v ...interface{})
func (l *Logger) Panic(v ...interface{})
func (l *Logger) Panicf(format string, v ...interface{})
func (l *Logger) Panicln(v ...interface{})
```
### 可以设置日志文件所在位置
当你调用第三方日志库时,可以通过设置 callpath来确定正确的位置
```
var (
buf bytes.Buffer
logger = log.New(&buf, "INFO: ", log.Lshortfile)
// infof callpath 为堆栈层级
// callpath 代表的层级关系
// main ->demo1 ->demo2->demo3->info
// 5 ->4 ->3 ->2 ->1
infof = func(info string) {
logger.Output(2, info)
}
)
func demo1() {
demo2()
}
func demo2() {
demo3()
}
func demo3() {
infof("Hello world")
}
func main() {
demo1()
fmt.Print(buf.String())
}
```
### log.SetFlags
```
Ldate = 1 << iota
Ltime
Lmicroseconds
Llongfile //显示觉得路径
Lshortfile // 显示文件名
LUTC
LstdFlags = Ldate | Ltime // 显示日期加时间
```
```
log.SetFlags(log.Lshortfile | log.Ltime)
log.Print("hello wrod") //13:45:38 test.go:16: hello wrod
```
### log.SetPrefix
```
log.Print("hello world") // 2020/12/27 13:57:08 hello world
log.SetPrefix("[debug]")
log.Print("hello world") // [debug]2020/12/27 13:57:08 hello world
```
### log.SetOutput 设置 Writer
重定向到文件
```
f, err := os.Create("1.log")
if err != nil {
log.Fatal(err)
}
defer f.Close()
log.Print("err1")
log.SetOutput(f)
log.Print("err2")
log.Panic("err3")
```
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