README
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log
Simple, fast, opinionated logging for command line applications 🪵
Project Description
log is a tiny and incredibly simple logging library designed to output nicely presented, human readable, levelled log messages. Ideal for command line applications ✨
There are many great logging libraries for Go out there, but so many of them are IMO too flexible and too complicated. I wanted a small, minimal dependency, opinionated logger I could use everywhere across all my Go projects (which are mostly command line applications). So I made one 🚀
Installation
go get github.com/FollowTheProcess/log@latest
Quickstart
package main
import (
"fmt"
"os"
"github.com/FollowTheProcess/log"
)
func main() {
logger := log.New(os.Stderr)
logger.Debug("Debug me") // By default this one won't show up, default log level is INFO
logger.Info("Some information here", "really", true)
logger.Warn("Uh oh!")
logger.Error("Goodbye")
}
Usage Guide
Make a new logger
logger := log.New(os.Stderr)
Levels
log provides a levelled logger with the normal levels you'd expect:
log.LevelDebug
log.LevelInfo
log.LevelWarn
log.LevelError
You write log lines at these levels with the corresponding methods on the Logger:
logger.Debug("...") // log.LevelDebug
logger.Info("...") // log.LevelInfo
logger.Warn("...") // log.LevelWarn
logger.Error("...") // log.LevelError
And you can configure a Logger to display logs at or higher than a particular level with the WithLevel option...
logger := log.New(os.Stderr, log.WithLevel(log.LevelDebug))
Key Value Pairs
log provides "semi structured" logs in that the message is free form text but you can attach arbitrary key value pairs to any of the log methods
logger.Info("Doing something", "cache", true, "duration", 30 * time.Second, "number", 42)
You can also create a "sub logger" with persistent key value pairs applied to every message
sub := logger.With("sub", true)
sub.Info("Hello from the sub logger", "subkey", "yes") // They can have their own per-method keys too!
Prefixes
log lets you apply a "prefix" to your logger, either as an option to log.New or by creating a "sub logger" with that prefix!
logger := log.New(os.Stderr, log.Prefix("http"))
Or...
logger := log.New(os.Stderr)
prefixed := logger.Prefixed("http")
Documentation
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Overview ¶
Package log provides a Logger primarily intended for terminal based command line programs.
The logs it produces are semi-structured with key value pairs being formatted as key=value but are primarily intended to be human readable and easy on the eye with a good choice of colours, ideal for command line applications that have a --debug or --verbose flag that enables extra logging.
log emphasis simplicity and efficiency so there aren't too many knobs to twiddle, you just get a consistent, easy to use, simple logger with minimal overhead.
Index ¶
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
func WithContext ¶ added in v0.2.0
WithContext stores the given logger in a context.Context.
The logger may be retrieved from the context with FromContext.
Types ¶
type Level ¶
type Level int
Level is a log level.
const ( // LevelDebug is the debug log level, intended for verbose logging modes or internal debugging. LevelDebug Level = -4 // LevelInfo is the info log level, this is the default level, intended for progress updates // and other informational messages. LevelInfo Level = 0 // LevelWarn is the warning log level, intended for raising recoverable issues to the user. Warning // logs should refer to events that are worth flagging to the user but the program can easily // recover from such as a missing configuration file when the application can fall back to defaults. LevelWarn Level = 4 // LevelError is the error log level. This is the highest log level provided by log and is intended // for signalling non-recoverable errors to the user. Typically followed by an actual go error and // possibly program exit. LevelError Level = 8 )
type Logger ¶
type Logger struct {
// contains filtered or unexported fields
}
Logger is a command line logger. It is safe to use across concurrently executing goroutines.
func FromContext ¶ added in v0.2.0
FromContext returns the Logger from a context.Context.
If the context does not contain a logger, a default logger is returned.
func New ¶
New returns a new Logger configured to write to w.
The logger can be configured by passing a number of functional options to set things like level, prefix etc.
func (*Logger) Prefixed ¶
Prefixed returns a new Logger with the given prefix.
The returned logger is otherwise an exact clone of the caller.
type Option ¶
type Option func(*Logger)
Option is a functional option for configuring a Logger.
func Prefix ¶
Prefix sets a prefix for the logger.
If set to a non-empty string, the prefix is shown on every log line prior to the message and any key value pairs.
func TimeFormat ¶
TimeFormat sets the format of the time information.
The layout is the standard Go time.Format and defaults to time.RFC3339.
Source Files
Directories