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Package log

import "github.com/rs/zerolog/log"
Overview
Index
Examples

Overview ▾

Package log provides a global logger for zerolog.

▾ Example

This example uses command-line flags to demonstrate various outputs depending on the chosen log level.

Code:

setup()
debug := flag.Bool("debug", false, "sets log level to debug")

flag.Parse()

// Default level for this example is info, unless debug flag is present
zerolog.SetGlobalLevel(zerolog.InfoLevel)
if *debug {
    zerolog.SetGlobalLevel(zerolog.DebugLevel)
}

log.Debug().Msg("This message appears only when log level set to Debug")
log.Info().Msg("This message appears when log level set to Debug or Info")

if e := log.Debug(); e.Enabled() {
    // Compute log output only if enabled.
    value := "bar"
    e.Str("foo", value).Msg("some debug message")
}

Output:

{"level":"info","time":1199811905,"message":"This message appears when log level set to Debug or Info"}

Variables

Logger is the global logger. 

var Logger = zerolog.New(os.Stderr).With().Timestamp().Logger()

func Ctx 

func Ctx(ctx context.Context) *zerolog.Logger

Ctx returns the Logger associated with the ctx. If no logger is associated, a disabled logger is returned.

func Debug 

func Debug() *zerolog.Event

Debug starts a new message with debug level.

You must call Msg on the returned event in order to send the event.

▾ Example

Example of a log at a particular "level" (in this case, "debug")

Code:

setup()
log.Debug().Msg("hello world")

Output:

{"level":"debug","time":1199811905,"message":"hello world"}

func Err 

func Err(err error) *zerolog.Event

Err starts a new message with error level with err as a field if not nil or with info level if err is nil.

You must call Msg on the returned event in order to send the event.

▾ Example

Example of a conditional level based on the presence of an error.

Code:

setup()
err := errors.New("some error")
log.Err(err).Msg("hello world")
log.Err(nil).Msg("hello world")

Output:

{"level":"error","error":"some error","time":1199811905,"message":"hello world"}
{"level":"info","time":1199811905,"message":"hello world"}

func Error 

func Error() *zerolog.Event

Error starts a new message with error level.

You must call Msg on the returned event in order to send the event.

▾ Example

Example of a log at a particular "level" (in this case, "error")

Code:

setup()
log.Error().Msg("hello world")

Output:

{"level":"error","time":1199811905,"message":"hello world"}

func Fatal 

func Fatal() *zerolog.Event

Fatal starts a new message with fatal level. The os.Exit(1) function is called by the Msg method.

You must call Msg on the returned event in order to send the event.

▾ Example

Example of a log at a particular "level" (in this case, "fatal")

Code:

setup()
err := errors.New("A repo man spends his life getting into tense situations")
service := "myservice"

log.Fatal().
    Err(err).
    Str("service", service).
    Msgf("Cannot start %s", service)

// Outputs: {"level":"fatal","time":1199811905,"error":"A repo man spends his life getting into tense situations","service":"myservice","message":"Cannot start myservice"}

func Hook 

func Hook(h zerolog.Hook) zerolog.Logger

Hook returns a logger with the h Hook.

func Info 

func Info() *zerolog.Event

Info starts a new message with info level.

You must call Msg on the returned event in order to send the event.

▾ Example

Example of a log at a particular "level" (in this case, "info")

Code:

setup()
log.Info().Msg("hello world")

Output:

{"level":"info","time":1199811905,"message":"hello world"}

func Level 

func Level(level zerolog.Level) zerolog.Logger

Level creates a child logger with the minimum accepted level set to level.

func Log 

func Log() *zerolog.Event

Log starts a new message with no level. Setting zerolog.GlobalLevel to zerolog.Disabled will still disable events produced by this method.

You must call Msg on the returned event in order to send the event.

▾ Example

Example of a log with no particular "level"

Code:

setup()
log.Log().Msg("hello world")

Output:

{"time":1199811905,"message":"hello world"}

func Output 

func Output(w io.Writer) zerolog.Logger

Output duplicates the global logger and sets w as its output.

func Panic 

func Panic() *zerolog.Event

Panic starts a new message with panic level. The message is also sent to the panic function.

You must call Msg on the returned event in order to send the event.

func Print 

func Print(v ...interface{})

Print sends a log event using debug level and no extra field. Arguments are handled in the manner of fmt.Print.

▾ Example

Simple logging example using the Print function in the log package Note that both Print and Printf are at the debug log level by default

Code:

setup()

log.Print("hello world")

Output:

{"level":"debug","time":1199811905,"message":"hello world"}

func Printf 

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

Printf sends a log event using debug level and no extra field. Arguments are handled in the manner of fmt.Printf.

▾ Example

Simple logging example using the Printf function in the log package

Code:

setup()

log.Printf("hello %s", "world")

Output:

{"level":"debug","time":1199811905,"message":"hello world"}

func Sample 

func Sample(s zerolog.Sampler) zerolog.Logger

Sample returns a logger with the s sampler.

func Trace 

func Trace() *zerolog.Event

Trace starts a new message with trace level.

You must call Msg on the returned event in order to send the event.

▾ Example

Example of a log at a particular "level" (in this case, "trace")

Code:

setup()
log.Trace().Msg("hello world")

Output:

{"level":"trace","time":1199811905,"message":"hello world"}

func Warn 

func Warn() *zerolog.Event

Warn starts a new message with warn level.

You must call Msg on the returned event in order to send the event.

▾ Example

Example of a log at a particular "level" (in this case, "warn")

Code:

setup()
log.Warn().Msg("hello world")

Output:

{"level":"warn","time":1199811905,"message":"hello world"}

func With 

func With() zerolog.Context

With creates a child logger with the field added to its context.

func WithLevel 

func WithLevel(level zerolog.Level) *zerolog.Event

WithLevel starts a new message with level.

You must call Msg on the returned event in order to send the event.