Log::Trace - provides a unified approach to tracing
# The tracing targets use Log::Trace; # No output use Log::Trace 'print'; # print to STDOUT use Log::Trace log => '/var/log/foo.log'; # Output to log file use Log::Trace print => { Level => 3 }; # Switch on/off logging with a constant use Log::Trace; import Log::Trace ('log' => LOGFILE) if TRACING; # Set up tracing for all packages that advertise TRACE use Foo; use Bar; use Log::Trace warn => { Deep => 1 }; # Sets up tracing in all subpackages excluding Foo use Log::Trace warn => {Deep => 1, 'Exclude' => 'Foo'}; # Exported functions TRACE("Record this..."); TRACE({Level => 2}, "Only shown if tracing level is 2 or higher"); TRACEF("A la printf: %d-%.2f", 1, 2.9999); TRACE_HERE(); # Record where we are (file, line, sub, args) DUMP(\@loh, \%hoh); # Trace out via Data::Dumper DUMP("Title", \@loh); # Trace out via Data::Dumper my $dump = DUMP(@args); # Dump is returned without being traced
A module to provide a unified approach to tracing. A script can use Log::Trace qw( < mode > ) to set the behaviour of the TRACE function.
use Log::Trace qw( < mode > )
By default, the trace functions are exported to the calling package only. You can export the trace functions to other packages with the Deep option. See "OPTIONS" for more information.
Deep
All exports are in uppercase (to minimise collisions with "real" functions).
Output a message. Where the message actually goes depends on how you imported Log::Trace (See "enabling Log::Trace"" in "Importing)
The first argument is an optional hashref of options:
TRACE('A simple message');
vs:
TRACE({ Level => 2.1 }, 'A message at a specified trace level');
printf() equivalent of TRACE. Also accepts an optional hashref:
printf()
TRACEF('%d items', scalar @items); TRACEF({ Level => 5 }, '$%1.2d', $value);
Serialises each of @args, optionally prepended with $message. If called in a non-void context, DUMP will return the serialised data rather than TRACE it. This is useful if you want to DUMP a datastructure at a specific tracing level.
DUMP('colours', [qw(red green blue)]); # outputs via TRACE my $dump = DUMP('colours', [qw(red green blue)]); # output returned
TRACEs the current position on the call stack (file, line number, subroutine name, subroutine args).
TRACE_HERE(); TRACE_HERE({Level => 99});
Controls where TRACE messages go. This method is called automatically when you call 'use Log::Trace;', but you may explicitly call this method at runtime. Compare the following:
'use Log::Trace;'
use Log::Trace 'print';
which is the same as
BEGIN { require Log::Trace; Log::Trace->import('print'); }
Valid combinations of $target and arg are:
$target
arg
Prints trace messages to the supplied $filehandle. Defaults to STDOUT if no file handle is specified.
$filehandle
STDOUT
Prints trace messages via warn()s to STDERR.
warn()
STDERR
Appends trace messages to a string reference.
Append trace messages to a file. If the file doesn't exist, it will be created.
This is equivalent to:
use Log::Trace file => $filename, {Verbose => 2};
Logs trace messages to syslog via Sys::Syslog, if available.
Sys::Syslog
You should consult your syslog configuration before using this option.
The default $priority is 'debug', and the ident is set to Log::Trace. You can configure the priority, but beyond that, you can implement your own syslogging via the custom trace target.
$priority
debug
ident
Log::Trace
priority
custom
Trace messages are processed by a custom subroutine. E.g.
use Log::Trace custom => \&mylogger; sub mylogger { my @messages = @_; foreach (@messages) { # highly sensitive trace messages! tr/a-zA-Z/n-za-mN-ZA-M/; print; } }
The import \%params are optional. These two statements are functionally the same:
\%params
import Log::Trace print => {Level => undef}; import Log::Trace 'print';
See "OPTIONS" for more information.
Note: If you use the custom tracing option, you should be careful about supplying a subroutine named TRACE.
TRACE
Attaches a TRACE statement to all subroutines in the package. This can be used to track the execution path of your code. It is particularly useful when used in conjunction with Deep and Everywhere options.
Everywhere
Note: Anonymous subroutines and AUTOLOAD are not TRACEd.
AUTOLOAD
By default, Log::Trace will only set up TRACE routines in modules that have already been loaded. This option overrides require() so that modules loaded after Log::Trace can automatically be set up for tracing.
require()
Note: This is an experimental feature. See the ENVIRONMENT NOTES for information about behaviour under different versions of perl.
This option has no effect on perl < 5.6
Attaches Log::Trace to all packages (that define a TRACE function). Any TRACEF, DUMP and TRACE_HERE routines will also be overridden in these packages.
Specify a serialiser to be used for DUMPing data structures.
This should either be a string naming a Data::Serializer backend (e.g. "YAML") or a hashref of parameters which will be passed to Data::Serializer, e.g.
{ serializer => 'XML::Dumper', options => { dtd => 'path/to/my.dtd' } }
Note that the raw_serialise() method of Data::Serializer is used. See Data::Serializer for more information.
If you do not have Data::Serializer installed, leave this option undefined to use the Data::Dumper natively.
Data::Serializer
Data::Dumper
Default: undef (use standalone Data::Dumper)
When used in conjunction with the Deep option, it will override the standard behaviour of only enabling tracing in packages that define TRACE stubs.
Default: false
Exclude a module or list of modules from tracing.
Specifies which trace levels to display.
If no Level is defined, all TRACE statements will be output.
Level
If the value is numeric, only TRACEs that are at the specified level or below will be output.
If the value is a list of numbers, only TRACEs that match the specified levels are output.
The level may also be a code reference which is passed the package name and the TRACE level. It mst return a true value if the TRACE is to be output.
Default: undef
Exports trace functions to packages that match the supplied regular expression. Can be used in conjunction with Exclude. You can also use Match as an exclusion method if you give it a negative look-ahead.
Exclude
Match
For example:
Match => qr/^(?!Acme::)/ # will exclude every module beginning with Acme::
and
Match => qr/^Acme::/ # does the reverse
Default: '.' # everything
You can use this option to prepend extra information to each trace message. The levels represent increasing levels of verbosity:
0: the default*, don't add anything 1: adds subroutine name and line number to the trace output 2: As [1], plus a filename and timestamp (in ISO 8601 : 2000 format)
This setting has no effect on the custom or log targets.
log
* the log target uses 'Verbose' level 2
The AutoImport feature overrides CORE::require() which requires perl 5.6, but you may see unexpected errors if you aren't using at least perl 5.8. The AutoImport option has no effect on perl < 5.6.
CORE::require()
In mod_perl or other persistent interpreter environments, different applications could trample on each other's TRACE routines if they use Deep (or Everywhere) option. For example application A could route all the trace output from Package::Foo into "appA.log" and then application B could import Log::Trace over the top, re-routing all the trace output from Package::Foo to "appB.log" for evermore. One way around this is to ensure you always import Log::Trace on every run in a persistent environment from all your applications that use the Deep option. We may provide some more tools to work around this in a later version of Log::Trace.
Log::Trace has not been tested in a multi-threaded application.
Carp Time::HiRes (used if available) Data::Dumper (used if available - necessary for meaningful DUMP output) Data::Serializer (optional - to customise DUMP output) Sys::Syslog (loaded on demand)
Log::TraceMessages is similar in design and purpose to Log::Trace. However, it only offers a subset of this module's functionality. Most notably, it doesn't offer a mechanism to control the tracing output of an entire application - tracing must be enabled on a module-by-module basis. Log::Trace also offers control over the output with the trace levels and supports more output targets.
Log::TraceMessages
Log::Agent offers a procedural interface to logging. It strikes a good balance between configurability and ease of use. It differs to Log::Trace in a number of ways. Log::Agent has a concept of channels and priorities, while Log::Trace only offers levels. Log::Trace also supports tracing code execution path and the Deep import option. Log::Trace trades a certain amount of configurability for increased ease-of use.
Log::Agent
A feature rich perl port of the popular log4j library for Java. It is object-oriented and comprised of more than 30 modules. It has an impressive feature set, but some people may be frightened of its complexity. In contrast, to use Log::Trace you need only remember up to 4 simple functions and a handful of configuration options.
log4j
Log::Trace::Manual - A guide to using Log::Trace
$Revision: 1.70 $ on $Date: 2005/11/01 11:32:59 $ by $Author: colinr $
John Alden and Simon Flack with some additions by Piers Kent and Wayne Myers <cpan _at_ bbc _dot_ co _dot_ uk>
(c) BBC 2005. This program is free software; you can redistribute it and/or modify it under the GNU GPL.
See the file COPYING in this distribution, or http://www.gnu.org/licenses/gpl.txt
To install Log::Trace, copy and paste the appropriate command in to your terminal.
cpanm
cpanm Log::Trace
CPAN shell
perl -MCPAN -e shell install Log::Trace
For more information on module installation, please visit the detailed CPAN module installation guide.