Badger::Log(3p)

NAME
Badger::Log - log for errors, warnings and other messages

SYNOPSIS
    use Badger::Log;

    my $log = Badger::Log->new({
        debug => 0,      # ignore debug messages
        info  => 1,      # print info messages
        warn  => \@warn, # add warnings to list
        error => $log2,  # delegate errors to $log2
        fatal => sub {   # custom fatal error handler
            my $message = shift;
            print "FATAL ERROR: $message\n";
        },
    });

    $log->debug('a debug message');
    $log->info('an info message');
    $log->warn('a warning message');
    $log->error('an error message');
    $log->fatal('a fatal error message');

DESCRIPTION
This module defines a simple base class module for logging messages generated by an application. It is intentionally very simple in design, providing the bare minimum in functionality with the possibility for extension by subclassing.

It offers little, if anything, over the many other fine logging modules available from CPAN. It exists to provide a basic logging facility that integrates cleanly with, and can be bundled up with the other Badger modules so that you've got something that works "out of the box".

There are five message categories:

debug
    A debugging message.

info
    A message providing some general information.

warn
    A warning message.

error
    An error message.

fatal
    A fatal error message.

CONFIGURATION OPTIONS

  debug
Flag to indicate if debugging messages should be generated and output. The default value is 0. It can be set to 1 to enable debugging messages or to one of the other reference values described in the documentation for the new() method.

  info
Flag to indicate if information messages should be generated and output. The default value is 0. It can be set to 1 to enable information messages or to one of the other reference values described in the documentation for the new() method.

  warn
Flag to indicate if warning messages should be generated and output. The default value is 1. It can be set to 0 to disable warning messages or to one of the other reference values described in the documentation for the new() method.

  error
Flag to indicate if error messages should be generated and output. The default value is 1. It can be set to 0 to disable error messages or to one of the other reference values described in the documentation for the new() method.

  fatal
Flag to indicate if fatal messages should be generated and output. The default value is 1. It can be set to 0 to disable fatal error messages (at your own peril) or to one of the other reference values described in the documentation for the new() method.

  format
This option can be used to define a different log message format.

    my $log = Badger::Log->new(
        format => '[<level>] [<time>] <message>',
    );

The default message format is:

    [<time>] [<system>] [<level>] <message>

The "<XXX>" snippets are replaced with their equivalent values:

    time        The current local time
    system      A system identifier, defaults to 'Badger'
    level       The message level: debug, info, warn, error or fatal
    message     The log message itself

The format can also be set using a $FORMAT package variable in a subclass of "Badger::Log".

    package Your::Log::Module;
    use base 'Badger::Log';
    our $FORMAT = '[<level>] [<time>] <message>';
    1;

  system
A system identifier which is inserted into each message via the "<system>" snippet. See format for further information. The default value is "Badger".

    my $log = Badger::Log->new(
        system => 'MyApp',
    );

The system identifier can also be set using a $SYSTEM package variable in a subclass of "Badger::Log".

    package Your::Log::Module;
    use base 'Badger::Log';
    our $SYSTEM = 'MyApp';
    1;

  strftime
This option can be used to set the format for the timestamp added to messages via the via the "<time<gt"> snippet.

    my $log = Badger::Log->new(
        strftime => '%a %b %d %Y',
    );

The format string is passed to the format() method of Badger::Timestamp.

METHODS

  new(\%options)
Constructor method which creates a new "Badger::Log" object. It accepts a list of named parameters or reference to hash of configuration options that define how each message type should be handled.

    my $log = Badger::Log->new({
        debug => 0,      # ignore debug messages
        info  => 1,      # print info messages
        warn  => \@warn, # add warnings to list
        error => $log2,  # delegate errors to $log2
        fatal => sub {   # custom fatal error handler
            my $message = shift;
            print "FATAL ERROR: $message\n";
        },
    });

Each message type can be set to 0 to ignore messages or 1 to have them printed to "STDERR". They can also be set to reference a list (the message is appended to the list), a subroutine (which is called, passing the message as an argument), or any object which implements a log() method (to which the message is delegated).

  debug($message)
Generate a debugging message.

    $log->debug('The cat sat on the mat');

  info($message)
Generate an information message.

    $log->info('The pod doors are closed');

  warn($message)
Generate a warning message.

    $log->warn('The pod doors are opening');

  error($message)
Generate an error message.

    $log->error("I'm sorry Dave, I can't do that');

  fatal($message)
Generate a fatal error message.

    $log->fatal('HAL is dead, aborting mission');

  debug_msg($format,@args)
This method uses the message() method inherited from Badger::Base to generate a debugging message from the arguments provided. To use this facility you first need to create your own logging subclass which defines the message formats that you want to use.

    package Your::Log;
    use base 'Badger::Log';

    our $MESSAGES = {
        denied => "Denied attempt by %s to %s",
    };

    1;

You can now use your logging module like so:

    use Your::Log;
    my $log = Your::Log->new;

    $log->debug_msg( denied => 'Arthur', 'make tea' );

The log message generated will look something like this:

# TODO

  info_msg($format,@args)
This method uses the message() method inherited from Badger::Base to generate an info message from the arguments provided. See debug_msg() for an example of using message formats.

  warn_msg($format,@args)
This method uses the message() method inherited from Badger::Base to generate a warning message from the arguments provided. See debug_msg() for an example of using message formats.

  error_msg($format,@args)
This method uses the message() method inherited from Badger::Base to generate an error message from the arguments provided. See debug_msg() for an example of using message formats.

  fatal_msg($format,@args)
This method uses the message() method inherited from Badger::Base to generate a fatal error message from the arguments provided. See debug_msg() for an example of using message formats.

  log($level, $message)
This is the general-purpose logging method that the above methods call.

    $log->log( info => 'star child is here' );

  level($level, $action)
This method is used to get or set the action for a particular level. When called with a single argument, it returns the current action for that level.

    my $debug = $log->level('debug');

When called with two arguments it sets the action for the log level to the second argument.

    $log->level( debug => 0 );      # disable
    $log->level( info  => 1 );      # enable
    $log->level( warn  => $list );  # push to list
    $log->level( error => $code );  # call code
    $log->level( fatal => $log2 );  # delegate to another log

  enable($level)
This method can be used to enable one or more logging levels.

    $log->enable('debug', 'info', 'warn');

  disable($level)
This method can be used to disable one or more logging levels.

    $log->disable('error', 'fatal');

INTERNAL METHODS

  _error_msg($format,@args)
The error_msg() method redefines the error_msg() method inherited from Badger::Base (which can be considered both a bug and a feature). The internal _error_msg() method effectively bypasses the new method and performs the same functionality as the base class method, in throwing an error as an exception.

  _fatal_msg($format,@args)
As per _error_msg(), this method provides access to the functionality of the fatal_msg() method in Badger::Base.

AUTHOR
Andy Wardley <http://wardley.org/>

COPYRIGHT
Copyright (C) 2005-2022 Andy Wardley. All Rights Reserved.

This module is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

SEE ALSO
Badger::Log::File