[log4perl-devel] Log::Log4perl Recipe of the Week (5)

[<msc...@ao...>]

Welcome to the Log::Log4perl recipe of the week. Today:

My application is already logging to a file. How
can I duplicate all messages to also go to the
screen?

Assuming that you already have a Log4perl
configuration file like

    log4perl.logger                    = DEBUG, FileApp

    log4perl.appender.FileApp          = Log::Dispatch::File
    log4perl.appender.FileApp.filename = test.log
    log4perl.appender.FileApp.layout   = PatternLayout
    log4perl.appender.FileApp.layout.ConversionPattern = %d> %m%n

and log statements all over your code, it's very
easy with Log4perl to have the same messages
both printed to the logfile and the screen. No
reason to change your code, of course, just add
another appender to the configuration file and
you're done:

    log4perl.logger                    = DEBUG, FileApp, ScreenApp

    log4perl.appender.FileApp          = Log::Dispatch::File
    log4perl.appender.FileApp.filename = test.log
    log4perl.appender.FileApp.layout   = PatternLayout
    log4perl.appender.FileApp.layout.ConversionPattern = %d> %m%n

    log4perl.appender.ScreenApp          = Log::Dispatch::Screen
    log4perl.appender.ScreenApp.stderr   = 0
    log4perl.appender.ScreenApp.layout   = PatternLayout
    log4perl.appender.ScreenApp.layout.ConversionPattern = %d> %m%n

The configuration file above is assuming that
both appenders are active in the same logger
hierarchy, in this case the "root" category. But
even if you've got file loggers defined in
several parts of your system, belonging to
different logger categories, each logging to
different files, you can gobble up all logged
messages by defining a root logger with a screen
appender, which would duplicate messages from all
your file loggers to the screen due to Log4perl's
appender inheritance. Check

    http://www.perl.com/pub/a/2002/09/11/log4perl.html

for details. Have fun!

-- 
-- Mike

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# Mike Schilli             #
# log...@pe... #
# http://perlmeister.com   #
# log4perl.sourceforge.net #
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