logger

Logger

This is a simple layer on top of the standard log package. Its main purpose is to give the developer separate log streams and logging severity levels.

The goal of this library is to be as simple as possible to use. It only adds the feature mentioned in the previous paragraph and nothing else.

You can see this package's documentation at godoc.org. It is much more than what you will find in this README.

Usage

Logging is as simple as

import (
    "github.com/ironsmile/logger"
)

func main() {
    logger.Errorf("I have an %d errors", 5)
    logger.SetLevel(logger.LevelDebug)
    logger.Debugln("A debug with a new line")
}

The above example uses the default logger. You can create as many loggers as you want:

func main() {
    lgStdOut := logger.New()
    lgStdOut.Log("Log object which logs to the stdout")

    outFile, _ := os.Create("/tmp/file.log")
    lgFile := logger.New()
    lgFile.SetLogOutput(outFile)
    lgFile.Log("This will be written in the log file")

    lgFile.SetErrorOutput(os.Stdout)
    lgFile.Errorln("This will be in the standard output")
}

You can take a look at the example file which showcases different usage scenarios.

Interface

Loggers support the Debug(f|ln)?, Log(f|ln)?, Error(f|ln)? and Fatal(f|ln)? functions which handle their arguments in the way fmt.Print(f|ln)? do. For more info regarding their arguments see the documentation.

A Logger is made up of 3 different exported log.Logger instances. Every one of them represents a logging stream. The Logger structure looks like this:

type Logger struct {
    Debugger *log.Logger
    Logger   *log.Logger
    Errorer  *log.Logger
    Level    int
}

As expected Debugger represents the debug stream, Logger - the logging and Errorer - the log stream. Being exported they can be used directly, possibly for configuration.

Logging Levels

Every Logger has a log level. There are 4 possible levels - LevelDebug, LevelLog, LevelError, LevelNoLog. See the package documentation for information on their usage.

Configuration

Use SetDebugOutput, SetLogOutput and SetErrorOutput to change the stream destination.

You can change the logging level by setting the Level property of a logger:

lg := logger.New()
lg.Level = logger.LevelDebug

For everything else you can access the underlying log.Logger instances directly.

Fatal functions

They do not have their own output stream but use the error stream. So there is no function SetFatalOutput and there is no property Fataller in the logger struct.

Underneath they actually use the log.Fatal functions which means a call to logger.Fatal(f|ln)? will print the message and halt the program.