How to Create a Folder (If Not Present) with Logger.New

How to create a folder (if not present) with Logger.new?

Try something like this.

  dir = File.dirname("#{Rails.root}/log/#{today}/my.log")

  FileUtils.mkdir_p(dir) unless File.directory?(dir)

  @@my_logger ||= Logger.new("#{Rails.root}/log/#{today}/my.log")

Python logging: create log if not exists or open and continue logging if it does

The logging module's FileHandler takes care of that for you. No need for complexity.

The handler takes an optional mode parameter, to specify whether it starts writing or appending data to it.

From the docs:

class logging.FileHandler(filename, mode='a', encoding=None, delay=False)

The specified file is opened and used as the stream for logging. If
mode is not specified, 'a' is used.

How to create a log folder before rails application loads the config.logger

Copy Paste it config/environments/development.rb

log_file_name = "#{Rails.root}/logs/#{ENV['RAILS_ENV']}.log"
unless File.exist?(File.dirname(log_file_name))
  FileUtils.mkdir_p(File.dirname(log_file_name))
  File.new(log_file_name, 'a+')
end

config.logger = ActiveSupport::BufferedLogger.new(File.join("#{Rails.root}", "logs", "#{ENV['RAILS_ENV']}.log"))

For 'a+' in File.new see this LINK

You can also use the config/application.rb LINK

Only create logs' directory if logger has file handler

The dictConfig() documentation shows how you can configure handlers of a particular type, and that can be extended to your own handlers.

You could subclass FileHandler and override the emit() method like this:

def emit(self, record):
    dn = os.path.dirname(self.baseFilename)
    if not os.path.exists(dn):
        os.makedirs(dn)
    super().emit(record)

and then use this subclass in your logging configuration. However, make sure you instantiate the handler with delay=True and, if you override __init__() in your custom handler, call the parent class' __init__() from there. The delay=True doesn't try to open the file until there is an actual need to write to it; that's done by the FileHandler.emit() method, and by creating the directory in the overridden method before calling the base class' emit() method, you'll only create the directory when it's needed and doesn't already exist.

How to create directories for Logger files through FileHandler

The j.u.l.FileHandler can't create directories. According to the API spec, nonexistent directories are and or should be treated as invalid. Which means your logs should appear in the user home directory instead. This described in JDK-6244047: impossible to specify directories to logging FileHandler unless they exist:

Configuration: By default each FileHandler is initialized using the
following LogManager configuration properties. If properties are not
defined (or have invalid values) then the specified default values
are used.

• java.util.logging.FileHandler.level specifies the default level
  for the Handler (defaults to Level.ALL).

<snip>

• java.util.logging.FileHandler.pattern specifies a pattern for
  generating the output file name. See below for details.
  (Defaults to "%h/java%u.log").

Based on the spec wording above, if the "FileHandler.pattern" property
specifies an unusable value, then it is invalid. If an invalid value
is specified, then the API is supposed to use the default value. In
this case "%h/java%u.log" should be used.

If you need to create directories then you can use the LogManager config option or subclass the FileHandler.

See also: JDK-6258319: No exception with FileHandler file has %h, but %h does not exist

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