不喜饶过

源码部分

type Logger struct {mu        sync.Mutex  // ensures atomic writes; protects the following fieldsprefix    string      // prefix on each line to identify the logger (but see Lmsgprefix)flag      int         // propertiesout       io.Writer   // destination for outputbuf       []byte      // for accumulating text to writeisDiscard atomic.Bool // whether out == io.Discard
}func New(out io.Writer, prefix string, flag int) *Logger {l := &Logger{out: out, prefix: prefix, flag: flag}if out == io.Discard {l.isDiscard.Store(true)}return l
}var std = New(os.Stderr, "", LstdFlags)// Default returns the standard logger used by the package-level output functions.
func Default() *Logger { return std }//对应结构体中的flag
const (Ldate         = 1 << iota     // the date in the local time zone: 2009/01/23Ltime                         // the time in the local time zone: 01:23:23Lmicroseconds                 // microsecond resolution: 01:23:23.123123.  assumes Ltime.Llongfile                     // full file name and line number: /a/b/c/d.go:23Lshortfile                    // final file name element and line number: d.go:23. overrides LlongfileLUTC                          // if Ldate or Ltime is set, use UTC rather than the local time zoneLmsgprefix                    // move the "prefix" from the beginning of the line to before the message//默认前缀放行首，log.Lmsgprefix 这个标记把前缀prefix放到消息message之前LstdFlags     = Ldate | Ltime // initial values for the standard logger
)

默认输出

输出	格式输出	换行输出	备注
log.Print()	log.Printf()	log.Println()	类似fmt.Print*
log.Fatal()	log.Fatalf()	log.Fatalln()	相当于log.Print* + os.Exit(1)
log.Panic()	log.Panicf()	log.Panicln	相当于log.Print* + panic()

自定义logger

	l1 := log.New(os.Stdout, "\t", log.LstdFlags|log.Lmsgprefix) //自定义loggerl1.Print("test")注： // 默认前缀放行首，log.Lmsgprefix 这个标记把前缀prefix放到消息message之前//os.Stdin  标准输入//os.Stdout 标准输出//os.Stderr 标准错误输出

文件输出

	f, err := os.OpenFile("d:/test.txt",os.O_CREATE|os.O_RDONLY|os.O_APPEND, // 只写 | 文件不存在创建 | 追加os.ModePerm,// os.FileMode()     chmod值，如0511 )if err != nil {log.Panicln(err)}defer f.Close()l2 := log.New(f, "\t", log.LstdFlags|log.Lmsgprefix)l2.Println("test")