Console Input (Arguments & Options)
===================================

The most interesting part of the commands are the arguments and options that
you can make available. These arguments and options allow you to pass dynamic
information from the terminal to the command.

Using Command Arguments
-----------------------

Arguments are the strings - separated by spaces - that
come after the command name itself. They are ordered, and can be optional
or required. For example, to add an optional ``last_name`` argument to the command
and make the ``name`` argument required::

    // ...
    use Symfony\Component\Console\Command\Command;
    use Symfony\Component\Console\Input\InputArgument;

    class GreetCommand extends Command
    {
        // ...

        protected function configure()
        {
            $this
                // ...
                ->addArgument('name', InputArgument::REQUIRED, 'Who do you want to greet?')
                ->addArgument('last_name', InputArgument::OPTIONAL, 'Your last name?')
            ;
        }
    }

You now have access to a ``last_name`` argument in your command::

    // ...
    use Symfony\Component\Console\Command\Command;
    use Symfony\Component\Console\Input\InputInterface;
    use Symfony\Component\Console\Output\OutputInterface;

    class GreetCommand extends Command
    {
        // ...

        protected function execute(InputInterface $input, OutputInterface $output)
        {
            $text = 'Hi '.$input->getArgument('name');

            $lastName = $input->getArgument('last_name');
            if ($lastName) {
                $text .= ' '.$lastName;
            }

            $output->writeln($text.'!');
        }
    }

The command can now be used in either of the following ways:

.. code-block:: terminal

    $ php bin/console app:greet Fabien
    Hi Fabien!

    $ php bin/console app:greet Fabien Potencier
    Hi Fabien Potencier!

It is also possible to let an argument take a list of values (imagine you want
to greet all your friends). Only the last argument can be a list::

    $this
        // ...
        ->addArgument(
            'names',
            InputArgument::IS_ARRAY,
            'Who do you want to greet (separate multiple names with a space)?'
        )
    ;

To use this, specify as many names as you want:

.. code-block:: terminal

    $ php bin/console app:greet Fabien Ryan Bernhard

You can access the ``names`` argument as an array::

    $names = $input->getArgument('names');
    if (count($names) > 0) {
        $text .= ' '.implode(', ', $names);
    }

There are three argument variants you can use:

``InputArgument::REQUIRED``
    The argument is mandatory. The command doesn't run if the argument isn't
    provided;

``InputArgument::OPTIONAL``
    The argument is optional and therefore can be omitted. This is the default
    behavior of arguments;

``InputArgument::IS_ARRAY``
    The argument can contain any number of values. For that reason, it must be
    used at the end of the argument list.

You can combine ``IS_ARRAY`` with ``REQUIRED`` and ``OPTIONAL`` like this::

    $this
        // ...
        ->addArgument(
            'names',
            InputArgument::IS_ARRAY | InputArgument::REQUIRED,
            'Who do you want to greet (separate multiple names with a space)?'
        )
    ;

Using Command Options
---------------------

Unlike arguments, options are not ordered (meaning you can specify them in any
order) and are specified with two dashes (e.g. ``--yell``). Options are
*always* optional, and can be setup to accept a value (e.g. ``--dir=src``) or
as a boolean flag without a value (e.g.  ``--yell``).

For example, add a new option to the command that can be used to specify
how many times in a row the message should be printed::

    // ...
    use Symfony\Component\Console\Input\InputOption;

    $this
        // ...
        ->addOption(
            'iterations',
            null,
            InputOption::VALUE_REQUIRED,
            'How many times should the message be printed?',
            1
        )
    ;

Next, use this in the command to print the message multiple times::

    for ($i = 0; $i < $input->getOption('iterations'); $i++) {
        $output->writeln($text);
    }

Now, when you run the command, you can optionally specify a ``--iterations``
flag:

.. code-block:: terminal

    # no --iterations provided, the default (1) is used
    $ php bin/console app:greet Fabien
    Hi Fabien!

    $ php bin/console app:greet Fabien --iterations=5
    Hi Fabien!
    Hi Fabien!
    Hi Fabien!
    Hi Fabien!
    Hi Fabien!

    # the order of options isn't important
    $ php bin/console app:greet Fabien --iterations=5 --yell
    $ php bin/console app:greet Fabien --yell --iterations=5
    $ php bin/console app:greet --yell --iterations=5 Fabien

.. tip::

    You can also declare a one-letter shortcut that you can call with a single
    dash, like ``-i``::

        $this
            // ...
            ->addOption(
                'iterations',
                'i',
                InputOption::VALUE_REQUIRED,
                'How many times should the message be printed?',
                1
            )
        ;

Note that to comply with the `docopt standard`_, long options can specify their
values after a white space or an ``=`` sign (e.g. ``--iterations 5`` or
``--iterations=5``), but short options can only use white spaces or no
separation at all (e.g. ``-i 5`` or ``-i5``).

.. caution::

    While it is possible to separate an option from its value with a white space,
    using this form leads to an ambiguity should the option appear before the
    command name. For example, ``php bin/console --iterations 5 app:greet Fabien``
    is ambiguous; Symfony would interpret ``5`` as the command name. To avoid
    this situation, always place options after the command name, or avoid using
    a space to separate the option name from its value.

There are four option variants you can use:

``InputOption::VALUE_IS_ARRAY``
    This option accepts multiple values (e.g. ``--dir=/foo --dir=/bar``);

``InputOption::VALUE_NONE``
    Do not accept input for this option (e.g. ``--yell``). This is the default
    behavior of options;

``InputOption::VALUE_REQUIRED``
    This value is required (e.g. ``--iterations=5`` or ``-i5``), the option
    itself is still optional;

``InputOption::VALUE_OPTIONAL``
    This option may or may not have a value (e.g. ``--yell`` or
    ``--yell=loud``).

You can combine ``VALUE_IS_ARRAY`` with ``VALUE_REQUIRED`` or
``VALUE_OPTIONAL`` like this::

    $this
        // ...
        ->addOption(
            'colors',
            null,
            InputOption::VALUE_REQUIRED | InputOption::VALUE_IS_ARRAY,
            'Which colors do you like?',
            ['blue', 'red']
        )
    ;

Options with optional arguments
-------------------------------

There is nothing forbidding you to create a command with an option that
optionally accepts a value, but it's a bit tricky. Consider this example::

    // ...
    use Symfony\Component\Console\Input\InputOption;

    $this
        // ...
        ->addOption(
            'yell',
            null,
            InputOption::VALUE_OPTIONAL,
            'Should I yell while greeting?'
        )
    ;

This option can be used in 3 ways: ``greet --yell``, ``greet yell=louder``,
and ``greet``. However, it's hard to distinguish between passing the option
without a value (``greet --yell``) and not passing the option (``greet``).

To solve this issue, you have to set the option's default value to ``false``::

    // ...
    use Symfony\Component\Console\Input\InputOption;

    $this
        // ...
        ->addOption(
            'yell',
            null,
            InputOption::VALUE_OPTIONAL,
            'Should I yell while greeting?',
            false // this is the new default value, instead of null
        )
    ;

Now it's possible to differentiate between not passing the option and not
passing any value for it::

    $optionValue = $input->getOption('yell');
    if (false === $optionValue) {
        // in this case, the option was not passed when running the command
        $yell = false;
        $yellLouder = false;
    } elseif (null === $optionValue) {
        // in this case, the option was passed when running the command
        // but no value was given to it
        $yell = true;
        $yellLouder = false;
    } else {
        // in this case, the option was passed when running the command and
        // some specific value was given to it
        $yell = true;
        if ('louder' === $optionValue) {
            $yellLouder = true;
        } else {
            $yellLouder = false;
        }
    }

The above code can be simplified as follows because ``false !== null``::

    $optionValue = $input->getOption('yell');
    $yell = ($optionValue !== false);
    $yellLouder = ($optionValue === 'louder');

.. _`docopt standard`: http://docopt.org/