term

Documentation

Overview

Package term provides tools for logging to a terminal.

Index

• Constants
• func IsTerminal(w io.Writer) bool
• func NewColorLogger(w io.Writer, newLogger func(io.Writer) log.Logger, ...) log.Logger
• func NewColorWriter(w io.Writer) io.Writer
• func NewLogger(w io.Writer, newLogger func(io.Writer) log.Logger, ...) log.Logger
• type Color
• type FgBgColor

Examples

• NewLogger (LevelColors)
• NewLogger (RedErrors)

Constants

const (
	Default = Color(iota)

	Black
	DarkRed
	DarkGreen
	Brown
	DarkBlue
	DarkMagenta
	DarkCyan
	Gray

	DarkGray
	Red
	Green
	Yellow
	Blue
	Magenta
	Cyan
	White
)

ANSI colors.

Functions

func IsTerminal

func IsTerminal(w io.Writer) bool

IsTerminal returns true if w writes to a terminal.

func NewColorLogger

func NewColorLogger(w io.Writer, newLogger func(io.Writer) log.Logger, color func(keyvals ...interface{}) FgBgColor) log.Logger

NewColorLogger returns a Logger which writes colored logs to w. ANSI color codes for the colors returned by color are added to the formatted output from the Logger returned by newLogger and the combined result written to w.

func NewColorWriter

func NewColorWriter(w io.Writer) io.Writer

NewColorWriter returns an io.Writer that writes to w and provides cross platform support for ANSI color codes. If w is not a terminal it is returned unmodified.

func NewLogger

func NewLogger(w io.Writer, newLogger func(io.Writer) log.Logger, color func(keyvals ...interface{}) FgBgColor) log.Logger

NewLogger returns a Logger that takes advantage of terminal features if possible. Log events are formatted by the Logger returned by newLogger. If w is a terminal each log event is colored according to the color function.

Example (LevelColors)

package main

import (
	"os"

	"github.com/go-kit/kit/log"
	"github.com/go-kit/kit/log/term"
)

func main() {
	// Color by level value
	colorFn := func(keyvals ...interface{}) term.FgBgColor {
		for i := 0; i < len(keyvals)-1; i += 2 {
			if keyvals[i] != "level" {
				continue
			}
			switch keyvals[i+1] {
			case "debug":
				return term.FgBgColor{Fg: term.DarkGray}
			case "info":
				return term.FgBgColor{Fg: term.Gray}
			case "warn":
				return term.FgBgColor{Fg: term.Yellow}
			case "error":
				return term.FgBgColor{Fg: term.Red}
			case "crit":
				return term.FgBgColor{Fg: term.Gray, Bg: term.DarkRed}
			default:
				return term.FgBgColor{}
			}
		}
		return term.FgBgColor{}
	}

	logger := term.NewLogger(os.Stdout, log.NewJSONLogger, colorFn)

	logger.Log("level", "warn", "msg", "yellow")
	logger.Log("level", "debug", "msg", "dark gray")
}

Example (RedErrors)

package main

import (
	"errors"
	"os"

	"github.com/go-kit/kit/log"
	"github.com/go-kit/kit/log/term"
)

func main() {
	// Color errors red
	colorFn := func(keyvals ...interface{}) term.FgBgColor {
		for i := 1; i < len(keyvals); i += 2 {
			if _, ok := keyvals[i].(error); ok {
				return term.FgBgColor{Fg: term.White, Bg: term.Red}
			}
		}
		return term.FgBgColor{}
	}

	logger := term.NewLogger(os.Stdout, log.NewLogfmtLogger, colorFn)

	logger.Log("msg", "default color", "err", nil)
	logger.Log("msg", "colored because of error", "err", errors.New("coloring error"))
}

Types

type Color

type Color uint8

Color represents an ANSI color. The zero value is Default.

type FgBgColor

type FgBgColor struct {
	Fg, Bg Color
}

FgBgColor represents a foreground and background color.