Overview

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 will add one. The Fatal functions call os.Exit(1) after
writing the log message. The Panic functions call panic after writing the log
message.

Index

• Constants
• func Fatalf(format string, v …interface{})
• func Flags() int
• func Panic(v …interface{})
• func Panicln(v …interface{})
• func Print(v …interface{})
• func Println(v …interface{})
• func SetOutput(w io.Writer)
• type Logger
  • func (l *Logger) Fatal(v …interface{})
  • func (l *Logger) Fatalln(v …interface{})
  • func (l *Logger) Output(calldepth int, s string) error
  • func (l *Logger) Panicf(format string, v …interface{})
  • func (l *Logger) Prefix() string
  • func (l *Logger) Println(v …interface{})
  • func (l *Logger) SetOutput(w io.Writer)

• Logger

Package files

Constants

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. 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 | Ltime | Lmicroseconds | Llongfile produce,

2009/01/23 01:23:23.123123 /a/b/c/d.go:23: message

func Fatal

func Fatal(v ...interface{})

Fatal is equivalent to Print() followed by a call to os.Exit(1).

func Fatalf

func Fatalf(format string, v ...interface{})

Fatalf is equivalent to Printf() followed by a call to os.Exit(1).

func
¶

func Fatalln(v ...interface{})

Fatalln is equivalent to Println() followed by a call to os.Exit(1).

func Flags() 

Flags returns the output flags for the standard logger.

func Output

func Output(calldepth int, s ) 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.

func
¶

func Panic(v ...interface{})

Panic is equivalent to Print() followed by a call to panic().

func
¶

func Panicf(format , v ...interface{})

Panicf is equivalent to Printf() followed by a call to panic().

func Panicln

func Panicln(v ...interface{})

Panicln is equivalent to Println() followed by a call to panic().

func Prefix

func Prefix() string

Prefix returns the output prefix for the standard logger.

func
¶

Print calls Output to print to the standard logger. Arguments are handled in the
manner of fmt.Print.

func Printf(format , v ...interface{})

Printf calls Output to print to the standard logger. Arguments are handled in
the manner of fmt.Printf.

func Println

func Println(v ...interface{})

Println calls Output to print to the standard logger. Arguments are handled in
the manner of fmt.Println.

func SetFlags

func SetFlags(flag int)

SetFlags sets the output flags for the standard logger.

func
¶

func SetOutput(w .Writer)

SetOutput sets the output destination for the standard logger.

func
¶

func SetPrefix(prefix )

SetPrefix sets the output prefix for the standard logger.

type Logger

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.

Example:

var (
    buf    bytes.Buffer
    logger = log.New(&buf, "logger: ", log.Lshortfile)
)
logger.Print("Hello, log file!")
fmt.Print(&buf)
// Output:
// logger: example_test.go:19: Hello, log file!

func
¶

func New(out .Writer, prefix , flag int) *

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. The flag argument defines the logging properties.

func (*Logger) Fatal

func (l *Logger) Fatal(v ...interface{})

Fatal is equivalent to l.Print() followed by a call to os.Exit(1).

func (*Logger)
¶

func (l *) Fatalf(format string, v ...interface{})

Fatalf is equivalent to l.Printf() followed by a call to os.Exit(1).

func (*Logger)
¶

func (l *) Fatalln(v ...interface{})

Fatalln is equivalent to l.Println() followed by a call to os.Exit(1).

Flags returns the output flags for the logger.

func (*Logger) Output

func (l *Logger) Output(calldepth , s string) 

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.

Example:

var (
    buf    bytes.Buffer
    logger = log.New(&buf, "INFO: ", log.Lshortfile)
    infof = func(info string) {
    }
)
infof("Hello world")
fmt.Print(&buf)
// Output:
// INFO: example_test.go:36: Hello world

func (*Logger)
¶

func (l *) Panic(v ...interface{})

Panic is equivalent to l.Print() followed by a call to panic().

func (*Logger) Panicf

func (l *Logger) Panicf(format , v ...interface{})

Panicf is equivalent to l.Printf() followed by a call to panic().

func (*Logger) Panicln

func (l *Logger) Panicln(v ...interface{})

Panicln is equivalent to l.Println() followed by a call to panic().

func (*Logger)
¶

func (l *) Prefix() string

Prefix returns the output prefix for the logger.

func (l *) Print(v ...interface{})

Print calls l.Output to print to the logger. Arguments are handled in the manner
of fmt.Print.

func (*Logger) Printf

func (l *Logger) Printf(format , v ...interface{})

Printf calls l.Output to print to the logger. Arguments are handled in the
manner of fmt.Printf.

func (*Logger) Println

func (l *Logger) Println(v ...interface{})

Println calls l.Output to print to the logger. Arguments are handled in the
manner of fmt.Println.

func (*Logger)
¶

func (l *) SetFlags(flag int)

SetFlags sets the output flags for the logger.

func (*Logger)
¶

func (l *) SetOutput(w io.)

SetOutput sets the output destination for the logger.

func (*Logger) SetPrefix

SetPrefix sets the output prefix for the logger.

Subdirectories