A simple message logging system.
Common Lisp
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README.md
simple-logger.asd

README.md

simple-logger

A simple message logging system.

Overview

This library provides a simple method of defining log messages and later showing them depending on the verbosity level.

Install

(ql:quickload :simple-logger)

Usage

To define a log message, you use DEFINE-MESSAGE, supplying a level, category, and message.

LEVEL Can be one of :TRACE, :DEBUG, :INFO, :WARN, :ERROR, or :FATAL.

CATEGORY A keyword symbol identifier for this message, to be referred to later when you want to emit it.

MESSAGE A string with the message, and any CL:FORMAT directives you want to include.

The global logging level by default is set to :INFO. This means that, unless the value of *CURRENT-LEVEL* is changed, then any messages defined with DEFINE-MESSAGE having a level lower than :INFO will not be displayed when the message is emitted.

To emit a message previously defined with DEFINE-MESSAGE, you use EMIT, giving it the category of the message you want to display, along with any other variables that are consumed by the CL:FORMAT string defined.

Example:

;; Change the global logging level to display messages with a level of :INFO or higher.
(setf *current-level* :info)

;; Define some messages.
(define-message :error :logger.example.error
  "Something bad happened. Arguments: ~{~A~^, ~}")
(define-message :debug :logger.example.hidden
  "This message is not displayed.")

;; Emit the example error message. This will print the following:
;; [ERROR] [2016-12-05 21:14:12] Something bad happened. Arguments: 1, 2, 3
(emit :logger.example.error '(1 2 3))

;; Emit the example debug message. This will not do anything at all because *CURRENT-LEVEL* is
;; higher than :DEBUG.

(emit :logger.example.hidden)

The global message level can be changed at a later time to start displaying messages that would have been hidden.

License

Copyright © 2016-2018 Michael Fiano.

Licensed under the MIT License.