Important

This library is no longer supported or updated by the Crystal Team, therefore we have archived the repository.

The contents are still available readonly and continue to work as a shards dependency.

If you wish to continue development yourself, we recommend you fork it. We can also arrange to transfer ownership.

If you have further question, please ask on https://forum.crystal-lang.org

logger

Provides the legacy Logger functionality.

Installation

1. Add the dependency to your shard.yml:

   dependencies:
     logger:
       github: crystal-lang/logger.cr

2. Run shards install

Usage

The Logger class provides a simple but sophisticated logging utility that you can use to output messages.

The messages have associated levels, such as INFO or ERROR that indicate their importance. You can then give the Logger a level, and only messages at that level or higher will be printed.

For instance, in a production system, you may have your Logger set to INFO or even WARN. When you are developing the system, however, you probably want to know about the program’s internal state, and would set the Logger to DEBUG.

Example

require "logger"

log = Logger.new(STDOUT)
log.level = Logger::WARN

# or
log = Logger.new(STDOUT, level: Logger::WARN)

log.debug("Created logger")
log.info("Program started")
log.warn("Nothing to do!")

begin
  File.each_line("/foo/bar.log") do |line|
    unless line =~ /^(\w+) = (.*)$/
      log.error("Line in wrong format: #{line}")
    end
  end
rescue err
  log.fatal("Caught exception; exiting")
  log.fatal(err)
end

If logging to multiple locations is required, an IO::MultiWriter can be used.

file = File.new("production.log", "a")
writer = IO::MultiWriter.new(file, STDOUT)

log = Logger.new(writer)
log.level = Logger::DEBUG
log.debug("Created logger")