SLF4O is a simple but flexible logging framework for GNU Octave, built on top of SLF4J and Apache Log4j. You can use it to do runtime-configurable logging from your Octave scripts and programs. This can be more informative and more manageable than commenting in and out fprintf() statements.
SLF4O provides:
- Logging functions (an Octave layer of bindings for SLF4J)
- A "Dispstr" API for customizing object display.
- A Log4j configuration GUI
The API is simple enough that you can get up and running with it quickly, or even use it casually in scripts, but it’s flexible and powerful enough to be useful for larger systems.
(The dispstr part is mostly optional; you don't have to learn it in order to use SLF4O logging.)
SLF4O is an Octave port of the SLF4M package for Matlab.
You can install SLF4O using Octave's pkg command:
pkg install https://github.com/apjanke/octave-slf4o/archive/master.zipIn your Octave session:
- Call
pkg load slf4oto load the SLF4O package.
In your Octave program:
- Call
logger.initSLF4O()to initialize SLF4O. This needs to be done before any logging calls are made.
The logging functions are in the +logger package. Call them from within your Octave
code. In order of logging level, they are:
- logger.error()
- logger.warn()
- logger.info()
- logger.debug()
- logger.trace()
The logging functions take sprintf()-style formatting arguments. You can also pass
an MException as the first argument to include the error message and stack
trace in the log message.
function helloWorld(x)
if nargin < 1 || isempty(x)
x = 123.456;
% These debug() calls will only show up if you set log level to DEBUG
logger.debug('Got empty x input; defaulted to %f', x);
end
z = x + 42;
logger.info('Answer z=%f', z);
if z > intmax('int32')
logger.warn('Large value z=%f will overflow int32', z);
end
try
some_bad_operation(x);
catch err
logger.error(err, 'Something went wrong in some_bad_operation(x=%f)', x);
end
endThe output looks like this:
>> helloWorld
16:53:18.279 INFO helloWorld() - Answer z=165.456000
16:53:18.291 ERROR helloWorld() - Something went wrong in some_bad_operation(123.456000)
Undefined function 'some_bad_operation' for input arguments of type 'double'.
Error in helloWorld (line 16)
some_bad_operation(x);
Thanks to dispstr(), you can also pass Octave objects to the %s conversions.
>> m = containers.Map;
>> m('foo') = 42; m('bar') = struct;
>> logger.info('Hello, world! %s', m)
09:52:29.809 INFO base - Hello, world! 2-by-1 containers.Map
To launch the configuration GUI, run logger.Log4jConfigurator.showGui. This GUI lets you set the logging levels and other attributes of the various loggers in your Octave session.
For more details, see the User's Guide.
Octave 4.4.1 or newer, built with Java enabled.
SLF4O is a thin layer built on top of SLF4J and Log4j. It is compatible with any other Java or Octave code that uses SLF4J or Log4j.
Log4j was chosen as the back-end because that’s what ships with Matlab, and SLF4O attempts to be maximally compatible with SLF4M.
SLF4O is licensed under the GNU General Public License, like GNU Octave itself.
SLF4O is developed by Andrew Janke. Its home page is the repo on GitHub.
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