#!perl
use strict;
use warnings;
use App::YG;

my $yg = App::YG->new;
$yg->run(@ARGV);

__END__

=encoding UTF-8

=head1 NAME

yg - log line filter, like \G of MySQL


=head1 SYNOPSIS

    $ yg [options] FILE ...

    or

    $ cat apache_log | yg [option]

    options:
        -p,  --parser         parser(default: apache-combined)
        -d,  --delimiter      the delimiter of log line(default: tab)
                              NOTE: if you set options -p and -d, it will use -d, -p option is ignored
        -n,  --number         if you specify delimiter and -n, then show number points
        -m,  --match          show log lines only if a keyword matches
        -re, --regexp         show log lines only if regular expression matches
        -i,  --ignore-case    regexp option: ignore case distinctions
        -r,  --raw            also show raw log lines
        -t,  --through        ignore yg command, output only raw log lines
             --digest         show digest of raw log string

        -h,  --help           show this help message
        -V,  --version        show version


=head1 EXAMPLES

parse Apache Combined logs, show logs vertically with labels of element

    $ yg apache_commbined_log

parse Apache Error logs, show logs vertically with labels of element

    $ yg -p apache-error apache_error_log

parse TAB-delimited logs, show logs vertically

    $ yg -d tab_delimited_log

parse TAB-delimited logs, show logs vertically with number labels

    $ yg -d -n tab_delimited_log

parse SPACE-delimited logs, show logs vertically

    $ yg -d space space_delimited_log

tailed log

    $ tail -f apache_commbined_log | yg


=head1 DESCRIPTION

C<yg> is a log viewer(filter) to show log lines vertically.

When you check apache logs, I guess you do like this

    $ cat apache_log
    127.0.0.1 - - [30/Sep/2012:12:34:56 +0900] "GET /foo HTTP/1.0" 200 123 "http://example.com/foo" "Mozilla/5.0"
    127.0.0.1 - - [30/Sep/2012:12:34:57 +0900] "GET /bar HTTP/1.0" 301 124 "http://example.com/bar" "Mozilla/5.1"

If you use C<yg>, log lines are showed like below:

    $ yg apache_log
    ******************** 1 ********************
         Host: 127.0.0.1
        Ident: -
     Authuser: -
         Date: 30/Sep/2012:12:34:56 +0900
      Request: GET /foo HTTP/1.0
       Status: 200
        Bytes: 123
      Referer: http://example.com/foo
    UserAgent: Mozilla/5.0

    ******************** 2 ********************
         Host: 127.0.0.1
        Ident: -
     Authuser: -
         Date: 30/Sep/2012:12:34:57 +0900
      Request: GET /bar HTTP/1.0
       Status: 200
        Bytes: 124
      Referer: http://example.com/bar
    UserAgent: Mozilla/5.1

easier for understanding.

Of course, C<yg> can work for like below.

    $ cat apache_log | yg

C<yg> command supports few formats of log. And you can write custom parser of L<App::YG>.

=head2 PARSERS

Above sample uses L<App::YG::Apache::Combined>. It is default parser. If you want to view other format logs, you should specify C<--parser> option.

    $ cat apache-error-log | yg --parser apache-error

Then C<yg> uses L<App::YG::Apache::Error> to parse log lines.

    $ cat apache-error-log | yg --parser apache-error
    ******************** 1 ********************
         Date: Sat Oct 06 17:34:17 2012
    Log_Level: error
       Client: 127.0.0.1
      Message: File does not exist: /var/www/html/favicon.ico

App::YG has below parsers.

=over 2

=item App::YG::Apache::Combined

for apache combined log

=item App::YG::Apache::Common

for apache common log

=item App::YG::Apache::Error

for apache error log

=item App::YG::Nginx::Main

for nginx main log

=back

=head3 HOW TO WRITE YOUR OWN PARSER

L<App::YG> is designed to be easily extensible. You might want to write a custom log parser. Each parser is easy to write one.

For example:

    package App::YG::MyApp::Log;
    use strict;
    use warnings;

    sub parse {
        my $line = shift;

        $line =~ m!^DATE:([^\t]+)\t([^\t]+)\tMSG:(.+)$! or warn "failed to parse line: '$line'\n";

        return [
            $1 || '',
            $2 || '',
            $3 || '',
        ];
    }

    sub labels {
        return [qw/
            Date
            Level
            Message
        /];
    }

Parser class must have 2 methods C<parser> and C<labels>. Both methods must return array reference. Let's look at the anatomy of App::YG::* modules. And check test codes in F<t/parser/*/*.t>.


=head1 AUTHOR

Dai Okabayashi E<lt>bayashi@cpan.orgE<gt>


=head1 SEE ALSO

L<App::YG>


=head1 LICENSE

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


=cut