Writing to the error output

If you rely on the output of a command (e.g. by redirecting it to a file for later reuse),

you may want to get only the relevant information outputted by the command, excluding progress

bars, notes, warnings and other error messages which have, most of the time, no value for reuse.

For excluding irrelevant messages from the output, you need to make your command write them to the error

output. Fortunately, the :class:`Symfony\\Component\\Console\\Style\\SymfonyStyle` provides a convenient

method to easily switch between both outputs:

:method:`Symfony\\Component\\Console\\Style\\SymfonyStyle::getErrorStyle`.

This method returns a new ``SymfonyStyle`` instance which makes use of the error output:

$io = new SymfonyStyle($input, $output);

// Write to the output

$io->write('Reusable information');

// Write to the error output

$io->getErrorStyle()->warning('Irrelevant warning');

.. note::

If you created the original ``SymfonyStyle`` instance with an ``OutputInterface`` object that is

not an instance of :class:`Symfony\\Component\\Console\\Output\ConsoleOutputInterface`, using

``getErrorStyle()`` will return an instance which makes use of the normal output instead of

the error one, as if you did not called the method.