We love logs because it helps us to debug during development. We also need a quick way to enable / disable logs because it’s not necessary for everybody :

• you maybe want logs during the development of your module
• people who will use it don’t necessary want to watch it

When testing a module and building a distribution, you maybe don’t want to inject dirt in your tests output. In the case of debuging, I think it’s a good thing to write it to a file and tail on it.

We’re gonna use two CPAN’s modules, Log::Minimal, a minimal but custimizable logger and File::Stamped, that allows stamped log file. They are not supposed to be build together, but Tokuhiro Matsuno(File::Stamped creator) recommend Log::Minimal in a code example.

My aim was to create a log system for the debug moment, because I was boring of using p() function from Data::Printer during my development and tests, because it was a bad thing: I was constantly adding and moving debug-print-code, that is a bad practice because it makes you repeat stupid tasks and encourage to test in a random way. I took a look at CPAN and Stack Overflow for some logging solutions, and Log::Log4Perl seems to be a recommended solution for most of serious apps. But it seems to much complicated to me, I don’t want to manage a new conf file, etc.

As Log::Minimal seems to be really simple to use, I’ve installed it and was very satisfacted of it quickly. Now, we are going to see how to use it to create a temporary file that will contain the traces.

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$ cpanm Log::Minimal File::Stamped

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use strict;
use warnings;

use Log::Minimal;
use File::Stamped;
use File::HomeDir;
use File::Spec::Function qw(catdir catfile);

$ENV{LM_DEBUG} = 1;

my $work_path = File::HomeDir->my_documents;

my $log_fh = File::Stamped->new(
  pattern => catdir( $work_path, "log.%Y-%m-%d.out"),
);
  
# Overrides Log::Minimal PRINT method
$Log::Minimal::PRINT = sub {
  my ( $time, $type, $message, $trace) = @_;

  # Removed $trace because it was too long in my environment
  print {$log_fh} "$time [$type] $message\n";
};

debugf("My::Module debugger init.");
debugf("Other");
debugf("interestant");
debugf("things...");

If you tail to /home/user/Documents/log.2013-09-24.out (adjust this to your own OS) from your terminal during your module tests…

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$ tail -vf /home/user/Douments/log.2013-09-24.out

… it will log the following :

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2013-09-24T19:28:38 [DEBUG] My::Module debugger init.
2013-09-24T19:28:39 [DEBUG] Other
2013-09-24T19:28:39 [DEBUG] interestant
2013-09-24T19:28:39 [DEBUG] things...

That was a very minimal blog post, but I hope it could be usefull. Thanx to nmishin for cross-platforming advices !