NAME Log::QnD - Quick and dirty logging system SYNOPSIS use Log::QnD; # create log entry my $qnd = Log::QnD->new('./log-file'); # save stuff into the log entry $qnd->{'stage'} = 1; $qnd->{'tracks'} = [qw{1 4}]; $qnd->{'coord'} = {x=>1, z=>42}; # undef the log entry or let it go out of scope undef $qnd; # the long entry looks like this: # {"stage":1,"tracks":["1","4"],"time":"Tue May 20 17:13:22 2014","coord":{"x":1,"z":42},"entry_id":"7WHHJ"} # get a log file object $log = Log::QnD::LogFile->new($log_path); # get entry from log $from_log = $log->get_entry(); DESCRIPTION Log::QnD is for creating quickly creating log files without a lot of setup. All you have to do is create a Log::QnD object with a file path. The returned object is a hashref into which you can save any data you want, including data nested in arrays and hashrefs. When the object goes out of scope its contents are saved to the log as a JSON string. PLEASE NOTE: Until this module reaches version 1.0, I might make some non-backwards-compatible changes. See Versions notes for such changes. INSTALLATION Log::QnD can be installed with the usual routine: perl Makefile.PL make make test make install Log::QnD A Log::QnD object represents a single log entry in a log file. It is created by calling Log::QnD->new() with the path to the log file: my $qnd = Log::QnD->new('./log-file'); That command alone is enough to create the log file if necessary and an entry into the log. It is not necessary to explicitly save the log entry; it will be saved when the Log::QnD object goes out of scope. By default, each log entry has two properties when it is created: the time the object was created ('time') and a (probably) unique ID ('entry_id'). The structure looks like this: { 'time' => 'Mon May 19 19:22:22 2014', 'entry_id' => 'JNnwk' } The 'time' field is the time the log entry was created. The 'entry_id' field is just a random five-character string. It is not checked for uniqueness, it is just probable that there is no other entry in the log with the same ID. Each log entry is stored as a single line in the log to make it easy to parse. Entries are separated by a blank line to make them more human-readable. So the entry above and another entry would be stored like this: {"time":"Mon May 19 19:22:22 2014","entry_id":"JNnwk"} {"time":"Mon May 19 19:22:23 2014","entry_id":"kjH0c"} You can save other values into the hash, including nested hashes and arrays: $qnd->{'stage'} = 1; $qnd->{'tracks'} = [qw{1 4}]; $qnd->{'coord'} = {x=>1, z=>42}; which results in a JSON string like this: {"stage":1,"tracks":["1","4"],"time":"Tue May 20 17:13:22 2014","coord":{"x":1,"z":42},"entry_id":"7WHHJ"} Methods Log::QnD->new($log_file_path) Create a new Log::QnD object. The only param for this method is the path to the log file. The log file does not need to actually exist yet; if necessary it will be created when the QnD object saves itself. $qnd->cancel() Cancels the automatic save. By default the $qnd object saves to the log when it goes out of scope, undeffing it won't cancel the save. $qnd->cancel() causes the object to not save when it goes out of scope. $qnd->uncancel() Sets the log entry object to automatically save when the object goes out of scope. By default the object is set to autosave, so uncancel() is only useful if you have cancelled the autosave in some way, such as with $qnd->cancel(). $qnd->save() Saves the Log::QnD log entry. By default, this method is called when the object goes out of scope. If you've used $qnd->cancel() to cancel autosave then you can use $qnd->save() to explicitly save the log entry. $qnd->log_file() Returns a Log::QnD::LogFile object. The log entry object does not hold on to the log file object, nor does the log file object "know" about the entry object. $qnd->private() $qnd->private() is a method inherited from Class::PublicPrivate . This method is used to store private properties such as the location of the log file. Unless you want to tinker around with the log entry's internals you can ignore this method. Log::QnD::LogFile A Log::QnD::LogFile object represents the log file to which the log entry is saved. The LogFile object does the actual work of saving the log entry. It also provides a mechanism for retrieving information from the log. If you use Log::QnD in its simplest form by just creating Log::QnD objects and allowing them to save themselves when they go out of scope then you don't need to explicitly use Log::QnD::LogFile. Methods Log::QnD::LogFile->new($log_file_path) Create a new Log::QnD::LogFile object. The only param for this method is the path to the log file. $log->write_entry($string) This method writes the log entry to the log file. The log file is created if it doesn't already exists. The only input for this method is the string to write to the log. The string should already be in JSON format and should have no newline. write_entry() doesn't do anything about formatting the string, it just spits it into the log. If the log already has data in it, then two newlines are added to the log file before the data is written. $log->get_entry() get_entry() returns a single entry from the log file. The data is already parsed from JSON. So, for example, the following line returns an entry from the log: $log->get_entry(); The last entry in the log file is returned first. With each subsequent call the next latest entry is returned. After the earliest entry in the log is returned then get_entry() returns undef. It is important to know that after the first call to get_entry() is made the log file object puts a read lock on the log file. That means that log entry objects cannot write to the file until the read lock is removed. The read lock is removed when the log file object is detroyed, when get_entry() returns undef, or when you explicitly call $log->end_read. option: entry_id If you send the 'entry_id' option then the log entry specified by the given id will be returned. If no such entry is found then undef is returned. For example, the following line returns the log entry for 'fv8sd', or undef if the entry is not found: $log->get_entry(entry_id=>'fv8sd'); $log->end_read() get_entry() explicitly closes the read handle for the log and releases the read lock. SEE ALSO The following modules provide similar functionality. I like mine best (or I wouldn't have written it) but your tastes may differ. Funny how the world works like that. Log::JSON Log::Message::JSON Mojo::Log::JSON TERMS AND CONDITIONS Copyright (c) 2014 by Miko O'Sullivan. All rights reserved. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself. This software comes with no warranty of any kind. AUTHOR Miko O'Sullivan miko@idocs.com TO DO Clean up POD In particular, I can't figure out how to link to sections in this page that have greater-than symbols in their names like $qnd->cancel() VERSIONS Version 0.10, May 20, 2014 Initial release. Version 0.11, May 22, 2014 Fixed problem in test script. Fixed incorrect documentation. Version 0.12, May 225, 2014 Made non-backwards-compatible change from "entry-id" to "entry_id". Added 'entry_id' option to $log_file->get_entry(). Added documentation for $qnd->private() method.