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info.rb

This Ruby code snippet demonstrates the use of the Logger class for logging messages at different severity levels. It initializes a logger that outputs to STDOUT, sets the logging level to INFO, and then logs messages at WARN, INFO, and DEBUG levels. Only WARN and INFO messages are displayed because the logger’s level is set to INFO, filtering out DEBUG messages. The output shows the severity level, timestamp, and the message itself.

Additional Note

Ref. https://docs.ruby-lang.org/ja/latest/library/logger.html

Ruby code snippet

require 'logger'
(irb):1: warning: logger was loaded from the standard library, but will no longer be part of the default gems starting from Ruby 3.5.0.
You can add logger to your Gemfile or gemspec to silence this warning.
#=> true

logger = Logger.new(STDOUT)
#=> 
#<Logger:0x00007f8e520165c0


puts "Level INFO"
Level INFO
#=> nil
logger.level = Logger::INFO # <= change level
#=> 1

logger.warn("Nothing to do!") # output
W, [2025-07-27T23:54:12.071561 #2950]  WARN -- : Nothing to do!
#=> true
logger.info("Program started") # output
I, [2025-07-27T23:54:12.072018 #2950]  INFO -- : Program started
#=> true
logger.debug("Created logger") # none
#=> true

Executed with Ruby 3.4.5.