go-logger

Simple logger for Go programs. Allows custom formats for messages.

Programming language: Go

License: BSD 3-clause "New" or "Revised" License

Tags: Logging    

Latest version: v1.3.0

README

go-logger

A simple go logger for easy logging in your programs. Allows setting custom format for messages.

Preview

[[Example Output](examples/example.png)](examples/example.go)

Install

go get github.com/apsdehal/go-logger

Use go get -u to update the package.

Example

Example [program](examples/example.go) demonstrates how to use the logger. See below for formatting instructions.

package main

import (
    "github.com/apsdehal/go-logger"
    "os"
)

func main () {
    // Get the instance for logger class, "test" is the module name, 1 is used to
    // state if we want coloring
    // Third option is optional and is instance of type io.Writer, defaults to os.Stderr
    log, err := logger.New("test", 1, os.Stdout)
    if err != nil {
        panic(err) // Check for error
    }

    // Critically log critical
    log.Critical("This is Critical!")
    log.CriticalF("%+v", err)
    // You can also use fmt compliant naming scheme such as log.Criticalf, log.Panicf etc
    // with small 'f'

    // Debug
    // Since default logging level is Info this won't print anything
    log.Debug("This is Debug!")
    log.DebugF("Here are some numbers: %d %d %f", 10, -3, 3.14)
    // Give the Warning
    log.Warning("This is Warning!")
    log.WarningF("This is Warning!")
    // Show the error
    log.Error("This is Error!")
    log.ErrorF("This is Error!")
    // Notice
    log.Notice("This is Notice!")
    log.NoticeF("%s %s", "This", "is Notice!")
    // Show the info
    log.Info("This is Info!")
    log.InfoF("This is %s!", "Info")

    log.StackAsError("Message before printing stack");

    // Show warning with format
    log.SetFormat("[%{module}] [%{level}] %{message}")
    log.Warning("This is Warning!") // output: "[test] [WARNING] This is Warning!"
    // Also you can set your format as default format for all new loggers
    logger.SetDefaultFormat("%{message}")
    log2, _ := logger.New("pkg", 1, os.Stdout)
    log2.Error("This is Error!") // output: "This is Error!"

    // Use log levels to set your log priority
    log2.SetLogLevel(DebugLevel)
    // This will be printed
    log2.Debug("This is debug!")
    log2.SetLogLevel(WarningLevel)
    // This won't be printed
    log2.Info("This is an error!")
}

Formatting

By default all log messages have format that you can see above (on pic). But you can override the default format and set format that you want.

You can do it for Logger instance (after creating logger) ...

log, _ := logger.New("pkgname", 1)
log.SetFormat(format)

... or for package

logger.SetDefaultFormat(format)

If you do it for package, all existing loggers will print log messages with format that these used already. But all newest loggers (which will be created after changing format for package) will use your specified format.

But anyway after this, you can still set format of message for specific Logger instance.

Format of log message must contains verbs that represent some info about current log entry. Ofc, format can contain not only verbs but also something else (for example text, digits, symbols, etc)

Format verbs:

You can use the following verbs:

%{id}           - means number of current log message
%{module}       - means module name (that you passed to func New())
%{time}         - means current time in format "2006-01-02 15:04:05"
%{time:format}  - means current time in format that you want
                    (supports all formats supported by go package "time")
%{level}        - means level name (upper case) of log message ("ERROR", "DEBUG", etc)
%{lvl}          - means first 3 letters of level name (upper case) of log message ("ERR", "DEB", etc)
%{file}         - means name of file in what you wanna write log
%{filename}     - means the same as %{file}
%{line}         - means line number of file in what you wanna write log
%{message}      - means your log message

Non-existent verbs (like %{nonex-verb} or %{}) will be replaced by an empty string. Invalid verbs (like %{inv-verb) will be treated as plain text.

Tests

Run:

• go test logger to run test on logger.
• go test -bench=. for benchmarks.

Thanks

Thanks goes to all go-loggers out there which I used as reference.

Contributors

Following contributors have made major contributions to go-logger:

• @qioalice
• @gjvnq
• @maezen

License

The BSD 3-Clause license, the same as the Go language.