log
import "log"
Package log implements a simple logging package. It defines a type, [Logger], with methods for formatting output. It also has a predefined 'standard' Logger accessible through helper functions Print[f|ln], Fatal[f|ln], and Panic[f|ln], which are easier to use than creating a Logger manually. That logger writes to standard error and prints the date and time of each logged message. Every log message is output on a separate line: if the message being printed does not end in a newline, the logger...
Go 1.26.1
Constants
const ( Ldate = 1 << iota // the date in the local time zone: 2009/01/23 Ltime // the time in the local time zone: 01:23:23 Lmicroseconds // m...
These flags define which text to prefix to each log entry generated by the [Logger]. Bits are or'ed together to control what's printed. With the exception of the Lmsgprefix flag, there is no control over the order they appear (the order listed here) or the format they present (as described in the comments). The prefix is followed by a colon only when Llongfile or Lshortfile is specified. For example, flags Ldate | Ltime (or LstdFlags) produce, 2009/01/23 01:23:23 message while flags Ldate ...
log/log.go:43
const ( Ldate = 1 << iota // the date in the local time zone: 2009/01/23 Ltime // the time in the local time zone: 01:23:23 Lmicroseconds // m...
These flags define which text to prefix to each log entry generated by the [Logger]. Bits are or'ed together to control what's printed. With the exception of the Lmsgprefix flag, there is no control over the order they appear (the order listed here) or the format they present (as described in the comments). The prefix is followed by a colon only when Llongfile or Lshortfile is specified. For example, flags Ldate | Ltime (or LstdFlags) produce, 2009/01/23 01:23:23 message while flags Ldate ...
log/log.go:46
const ( Ldate = 1 << iota // the date in the local time zone: 2009/01/23 Ltime // the time in the local time zone: 01:23:23 Lmicroseconds // m...
These flags define which text to prefix to each log entry generated by the [Logger]. Bits are or'ed together to control what's printed. With the exception of the Lmsgprefix flag, there is no control over the order they appear (the order listed here) or the format they present (as described in the comments). The prefix is followed by a colon only when Llongfile or Lshortfile is specified. For example, flags Ldate | Ltime (or LstdFlags) produce, 2009/01/23 01:23:23 message while flags Ldate ...
log/log.go:45
const ( Ldate = 1 << iota // the date in the local time zone: 2009/01/23 Ltime // the time in the local time zone: 01:23:23 Lmicroseconds // m...
These flags define which text to prefix to each log entry generated by the [Logger]. Bits are or'ed together to control what's printed. With the exception of the Lmsgprefix flag, there is no control over the order they appear (the order listed here) or the format they present (as described in the comments). The prefix is followed by a colon only when Llongfile or Lshortfile is specified. For example, flags Ldate | Ltime (or LstdFlags) produce, 2009/01/23 01:23:23 message while flags Ldate ...
log/log.go:49
const ( Ldate = 1 << iota // the date in the local time zone: 2009/01/23 Ltime // the time in the local time zone: 01:23:23 Lmicroseconds // m...
These flags define which text to prefix to each log entry generated by the [Logger]. Bits are or'ed together to control what's printed. With the exception of the Lmsgprefix flag, there is no control over the order they appear (the order listed here) or the format they present (as described in the comments). The prefix is followed by a colon only when Llongfile or Lshortfile is specified. For example, flags Ldate | Ltime (or LstdFlags) produce, 2009/01/23 01:23:23 message while flags Ldate ...
log/log.go:47
const ( Ldate = 1 << iota // the date in the local time zone: 2009/01/23 Ltime // the time in the local time zone: 01:23:23 Lmicroseconds // m...
These flags define which text to prefix to each log entry generated by the [Logger]. Bits are or'ed together to control what's printed. With the exception of the Lmsgprefix flag, there is no control over the order they appear (the order listed here) or the format they present (as described in the comments). The prefix is followed by a colon only when Llongfile or Lshortfile is specified. For example, flags Ldate | Ltime (or LstdFlags) produce, 2009/01/23 01:23:23 message while flags Ldate ...
log/log.go:50
const ( Ldate = 1 << iota // the date in the local time zone: 2009/01/23 Ltime // the time in the local time zone: 01:23:23 Lmicroseconds // m...
These flags define which text to prefix to each log entry generated by the [Logger]. Bits are or'ed together to control what's printed. With the exception of the Lmsgprefix flag, there is no control over the order they appear (the order listed here) or the format they present (as described in the comments). The prefix is followed by a colon only when Llongfile or Lshortfile is specified. For example, flags Ldate | Ltime (or LstdFlags) produce, 2009/01/23 01:23:23 message while flags Ldate ...
log/log.go:44
const ( Ldate = 1 << iota // the date in the local time zone: 2009/01/23 Ltime // the time in the local time zone: 01:23:23 Lmicroseconds // m...
These flags define which text to prefix to each log entry generated by the [Logger]. Bits are or'ed together to control what's printed. With the exception of the Lmsgprefix flag, there is no control over the order they appear (the order listed here) or the format they present (as described in the comments). The prefix is followed by a colon only when Llongfile or Lshortfile is specified. For example, flags Ldate | Ltime (or LstdFlags) produce, 2009/01/23 01:23:23 message while flags Ldate ...
log/log.go:48
Functions
func Default() *Logger
Default returns the standard logger used by the package-level output functions.
log/log.go:90
func Fatal(v ...any)
Fatal is equivalent to [Print] followed by a call to [os.Exit](1).
log/log.go:422
func Fatalf(format string, v ...any)
Fatalf is equivalent to [Printf] followed by a call to [os.Exit](1).
log/log.go:430
func Fatalln(v ...any)
Fatalln is equivalent to [Println] followed by a call to [os.Exit](1).
log/log.go:438
func Flags() int
Flags returns the output flags for the standard logger. The flag bits are [Ldate], [Ltime], and so on.
log/log.go:370
func New(out io.Writer, prefix string, flag int) *Logger
New creates a new [Logger]. The out variable sets the destination to which log data will be written. The prefix appears at the beginning of each generated log line, or after the log header if the [Lmsgprefix] flag is provided. The flag argument defines the logging properties.
log/log.go:71
func Output(calldepth int, s string) error
Output writes the output for a logging event. The string s contains the text to print after the prefix specified by the flags of the Logger. A newline is appended if the last character of s is not already a newline. Calldepth is the count of the number of frames to skip when computing the file name and line number if [Llongfile] or [Lshortfile] is set; a value of 1 will print the details for the caller of Output.
log/log.go:479
func Panic(v ...any)
Panic is equivalent to [Print] followed by a call to panic().
log/log.go:446
func Panicf(format string, v ...any)
Panicf is equivalent to [Printf] followed by a call to panic().
log/log.go:455
func Panicln(v ...any)
Panicln is equivalent to [Println] followed by a call to panic().
log/log.go:464
func Prefix() string
Prefix returns the output prefix for the standard logger.
log/log.go:381
func Print(v ...any)
Print calls Output to print to the standard logger. Arguments are handled in the manner of [fmt.Print].
log/log.go:399
func Printf(format string, v ...any)
Printf calls Output to print to the standard logger. Arguments are handled in the manner of [fmt.Printf].
log/log.go:407
func Println(v ...any)
Println calls Output to print to the standard logger. Arguments are handled in the manner of [fmt.Println].
log/log.go:415
func SetFlags(flag int)
SetFlags sets the output flags for the standard logger. The flag bits are [Ldate], [Ltime], and so on.
log/log.go:376
func SetOutput(w io.Writer)
SetOutput sets the output destination for the standard logger.
log/log.go:364
func SetPrefix(prefix string)
SetPrefix sets the output prefix for the standard logger.
log/log.go:386
func Writer() io.Writer
Writer returns the output destination for the standard logger.
log/log.go:391
Types
type Logger struct {
// contains filtered or unexported fields
}A Logger represents an active logging object that generates lines of output to an [io.Writer]. Each logging operation makes a single call to the Writer's Write method. A Logger can be used simultaneously from multiple goroutines; it guarantees to serialize access to the Writer.
log/log.go:57
func (l *Logger) Fatal(v ...any)
Fatal is equivalent to l.Print() followed by a call to [os.Exit](1).
log/log.go:281
func (l *Logger) Fatalf(format string, v ...any)
Fatalf is equivalent to l.Printf() followed by a call to [os.Exit](1).
log/log.go:289
func (l *Logger) Fatalln(v ...any)
Fatalln is equivalent to l.Println() followed by a call to [os.Exit](1).
log/log.go:297
func (l *Logger) Flags() int
Flags returns the output flags for the logger. The flag bits are [Ldate], [Ltime], and so on.
log/log.go:333
func (l *Logger) Output(calldepth int, s string) error
Output writes the output for a logging event. The string s contains the text to print after the prefix specified by the flags of the Logger. A newline is appended if the last character of s is not already a newline. Calldepth is used to recover the PC and is provided for generality, although at the moment on all pre-defined paths it will be 2.
log/log.go:193
func (l *Logger) Panic(v ...any)
Panic is equivalent to l.Print() followed by a call to panic().
log/log.go:305
func (l *Logger) Panicf(format string, v ...any)
Panicf is equivalent to l.Printf() followed by a call to panic().
log/log.go:314
func (l *Logger) Panicln(v ...any)
Panicln is equivalent to l.Println() followed by a call to panic().
log/log.go:323
func (l *Logger) Prefix() string
Prefix returns the output prefix for the logger.
log/log.go:344
func (l *Logger) Print(v ...any)
Print calls l.Output to print to the logger. Arguments are handled in the manner of [fmt.Print].
log/log.go:258
func (l *Logger) Printf(format string, v ...any)
Printf calls l.Output to print to the logger. Arguments are handled in the manner of [fmt.Printf].
log/log.go:266
func (l *Logger) Println(v ...any)
Println calls l.Output to print to the logger. Arguments are handled in the manner of [fmt.Println].
log/log.go:274
func (l *Logger) SetFlags(flag int)
SetFlags sets the output flags for the logger. The flag bits are [Ldate], [Ltime], and so on.
log/log.go:339
func (l *Logger) SetOutput(w io.Writer)
SetOutput sets the output destination for the logger.
log/log.go:80
func (l *Logger) SetPrefix(prefix string)
SetPrefix sets the output prefix for the logger.
log/log.go:352
func (l *Logger) Writer() io.Writer
Writer returns the output destination for the logger.
log/log.go:357