Golang logging library

Package logging implements a logging infrastructure for Go. It supports different logging backends like syslog, file and memory. Multiple backends can be utilized with different log levels per backend and logger.

Installing

Using go get

$ go get github.com/op/go-logging

After this command go-logging is ready to use. Its source will be in:

$GOROOT/src/pkg/github.com/op/go-logging

You can use go get -u -a to update all installed packages.

Example

You can find a more detailed example at the end.

package main

import "github.com/op/go-logging"

var log = logging.MustGetLogger("package.example")

func main() {
	var format = logging.MustStringFormatter("%{level} %{message}")
	logging.SetFormatter(format)
	logging.SetLevel(logging.INFO, "package.example")

	log.Debug("hello %s", "golang")
	log.Info("hello %s", "golang")
}

Documentation

For docs, see http://godoc.org/github.com/op/go-logging or run:

$ go doc github.com/op/go-logging

Full example

package main

import (
	stdlog "log"
	"os"

	"github.com/op/go-logging"
)

var log = logging.MustGetLogger("test")

type Password string

func (p Password) Redacted() interface{} {
	return logging.Redact(string(p))
}

func main() {
	// Customize the output format
	logging.SetFormatter(logging.MustStringFormatter("▶ %{level:.1s} 0x%{id:x} %{message}"))

	// Setup one stdout and one syslog backend.
	logBackend := logging.NewLogBackend(os.Stderr, "", stdlog.LstdFlags|stdlog.Lshortfile)
	logBackend.Color = true

	syslogBackend, err := logging.NewSyslogBackend("")
	if err != nil {
		log.Fatal(err)
	}

	// Combine them both into one logging backend.
	logging.SetBackend(logBackend, syslogBackend)

	// Run one with debug setup for "test" and one with error.
	for _, level := range []logging.Level{logging.DEBUG, logging.ERROR} {
		logging.SetLevel(level, "test")

		log.Critical("crit")
		log.Error("err")
		log.Warning("warning")
		log.Notice("notice")
		log.Info("info")
		log.Debug("debug %s", Password("secret"))
	}
}