Log4perl category as log file name - log4perl

Question

I'm sure I'm being dim and missing the obvious but is there a simple way of using the current category as the filename in a config file without resorting to a subroutine call?
So that in the following one could use ${category}.log instead of repeating bin.nh.tpp in the filename line
log4perl.logger.**bin.nh.tpp**=INFO, BIN_NH_TPP_LOGFILE
log4perl.appender.BIN_NH_TPP_LOGFILE=Log::Log4perl::Appender::File
log4perl.appender.BIN_NH_TPP_LOGFILE.filename=${LOGS}/nh/**bin.nh.tpp**.log
log4perl.appender.BIN_NH_TPP_LOGFILE.mode=append
log4perl.appender.BIN_NH_TPP_LOGFILE.layout=PatternLayout
log4perl.appender.BIN_NH_TPP_LOGFILE.layout.ConversionPattern=[%d] %F{1} %L %c - %m%n

Answer 1

It's somewhat more involved than a subroutine, I'm afraid. Subroutines in l4p conf files allow for including variables known at conf file parsing time, e.g. the time/date or a user id. You can't modify log time behavior that way.
The easiest way I can think of right now to accomplish what you want is a custom appender like
package FileByCategoryAppender;
use warnings;
use strict;
use base qw( Log::Log4perl::Appender::File );
sub new {
my( $class, %options ) = #_;
$options{filename } = "no-category.log";
my $self = $class->SUPER::new( %options );
bless $self, $class;
}
sub log {
my( $self, %params ) = #_;
my $category = $params{ log4p_category };
$self->SUPER::file_switch( $category . ".log" );
$self->SUPER::log( %params );
}
1;
and then use it in your script like
use strict;
use warnings;
use Log::Log4perl qw( get_logger );
my $conf = q(
log4perl.category = WARN, Logfile
log4perl.appender.Logfile = FileByCategoryAppender
log4perl.appender.Logfile.create_at_logtime = 1
log4perl.appender.Logfile.layout = \
Log::Log4perl::Layout::PatternLayout
log4perl.appender.Logfile.layout.ConversionPattern = %d %F{1} %L> %m %n
);
Log::Log4perl::init(\$conf);
my $logger = get_logger("Bar::Twix");
$logger->error("twix error");
$logger = get_logger("Bar::Mars");
$logger->error("mars error");
which will result in two log files being created at log time:
# Bar.Mars.log
2012/11/18 11:12:12 t 21> mars error
and
# Bar.Twix.log
2012/11/18 11:12:12 t 21> twix error