Log::Log4perl::Config - Log4perl configuration file syntax
In Log::Log4perl, configuration files are used to describe how the system's loggers ought to behave.
Log::Log4perl
The format is the same as the one as used for log4j, just with a few perl-specific extensions, like enabling the Bar::Twix syntax instead of insisting on the Java-specific Bar.Twix.
log4j
Bar::Twix
Bar.Twix
Comment lines (starting with arbitrary whitespace and a #) and blank lines (all whitespace or empty) are ignored.
Also, blanks between syntactical entities are ignored, it doesn't matter if you write
log4perl.logger.Bar.Twix=WARN,Screen
or
log4perl.logger.Bar.Twix = WARN, Screen
Log::Log4perl will strip the blanks while parsing your input.
Assignments need to be on a single line. However, you can break the line if you want to by using a continuation character at the end of the line. Instead of writing
log4perl.appender.A1.layout=Log::Log4perl::Layout::SimpleLayout
you can break the line at any point by putting a backslash at the very (!) end of the line to be continued:
log4perl.appender.A1.layout=\ Log::Log4perl::Layout::SimpleLayout
Watch out for trailing blanks after the backslash, which would prevent the line from being properly concatenated.
Loggers are addressed by category:
This sets all loggers under the Bar::Twix hierarchy on priority WARN and attaches a later-to-be-defined Screen appender to them. Settings for the root appender (which doesn't have a name) can be accomplished by simply omitting the name:
WARN
Screen
log4perl.logger = FATAL, Database, Mailer
This sets the root appender's level to FATAL and also attaches the later-to-be-defined appenders Database and Mailer to it.
FATAL
Database
Mailer
The additivity flag of a logger is set or cleared via the additivity keyword:
additivity
log4perl.additivity.Bar.Twix = 0|1
(Note the reversed order of keyword and logger name, resulting from the dilemma that a logger name could end in .additivity according to the log4j documentation).
.additivity
Appender names used in Log4perl configuration file lines need to be resolved later on, in order to define the appender's properties and its layout. To specify properties of an appender, just use the appender keyword after the log4perl intro and the appender's name:
appender
log4perl
# The Bar::Twix logger and its appender log4perl.logger.Bar.Twix = DEBUG, A1 log4perl.appender.A1=Log::Log4perl::Appender::File log4perl.appender.A1.filename=test.log log4perl.appender.A1.mode=append log4perl.appender.A1.layout=Log::Log4perl::Layout::SimpleLayout
This sets a priority of DEBUG for loggers in the Bar::Twix hierarchy and assigns the A1 appender to it, which is later on resolved to be an appender of type Log::Log4perl::Appender::File, simply appending to a log file. According to the Log::Log4perl::Appender::File manpage, the filename parameter specifies the name of the log file and the mode parameter can be set to append or write (the former will append to the logfile if one with the specified name already exists while the latter would clobber and overwrite it).
DEBUG
A1
Log::Log4perl::Appender::File
filename
mode
append
write
The order of the entries in the configuration file is not important, Log::Log4perl will read in the entire file first and try to make sense of the lines after it knows the entire context.
You can very well define all loggers first and then their appenders (you could even define your appenders first and then your loggers, but let's not go there):
log4perl.logger.Bar.Twix = DEBUG, A1 log4perl.logger.Bar.Snickers = FATAL, A2 log4perl.appender.A1=Log::Log4perl::Appender::File log4perl.appender.A1.filename=test.log log4perl.appender.A1.mode=append log4perl.appender.A1.layout=Log::Log4perl::Layout::SimpleLayout log4perl.appender.A2=Log::Log4perl::Appender::Screen log4perl.appender.A2.stderr=0 log4perl.appender.A2.layout=Log::Log4perl::Layout::PatternLayout log4perl.appender.A2.layout.ConversionPattern = %d %m %n
Note that you have to specify the full path to the layout class and that ConversionPattern is the keyword to specify the printf-style formatting instructions.
ConversionPattern
Here's some examples of often-used Log4perl configuration files:
log4perl.category.Bar.Twix = WARN, Screen log4perl.appender.Screen = Log::Log4perl::Appender::Screen log4perl.appender.Screen.layout = \ Log::Log4perl::Layout::PatternLayout log4perl.appender.Screen.layout.ConversionPattern = %d %m %n
log4perl.category.Bar.Twix = WARN, Screen log4perl.appender.Screen = Log::Log4perl::Appender::Screen log4perl.appender.Screen.stderr = 0 log4perl.appender.Screen.layout = \ Log::Log4perl::Layout::PatternLayout log4perl.appender.Screen.layout.ConversionPattern = %d %m %n
log4perl.logger.Bar.Twix = DEBUG, A1 log4perl.appender.A1=Log::Log4perl::Appender::File log4perl.appender.A1.filename=test.log log4perl.appender.A1.mode=append log4perl.appender.A1.layout = \ Log::Log4perl::Layout::PatternLayout log4perl.appender.A1.layout.ConversionPattern = %d %m %n
Note that you could even leave out
log4perl.appender.A1.mode=append
and still have the logger append to the logfile by default, although the Log::Log4perl::Appender::File module does exactly the opposite. This is due to some nasty trickery Log::Log4perl performs behind the scenes to make sure that beginner's CGI applications don't clobber the log file every time they're called.
If you loathe the Log::Log4perl's append-by-default strategy, you can certainly override it:
log4perl.logger.Bar.Twix = DEBUG, A1 log4perl.appender.A1=Log::Log4perl::Appender::File log4perl.appender.A1.filename=test.log log4perl.appender.A1.mode=write log4perl.appender.A1.layout=Log::Log4perl::Layout::SimpleLayout
write is the mode that has Log::Log4perl::Appender::File explicitely clobber the log file if it exists.
Mike Schilli, <log4perl@perlmeister.com>
Log::Log4perl::Config::PropertyConfigurator
Log::Log4perl::Config::DOMConfigurator
Log::Log4perl::Config::LDAPConfigurator (coming soon!)
To install Log::Log4perl, copy and paste the appropriate command in to your terminal.
cpanm
cpanm Log::Log4perl
CPAN shell
perl -MCPAN -e shell install Log::Log4perl
For more information on module installation, please visit the detailed CPAN module installation guide.