Understanding how Console Arguments Are Handled

It can be difficult to understand the way arguments are handled by the console application. The Symfony Console application, like many other CLI utility tools, follows the behavior described in the docopt standards.

Have a look at the following command that has three options:

namespace Acme\Console\Command;

use Symfony\Component\Console\Command\Command;
use Symfony\Component\Console\Input\InputArgument;
use Symfony\Component\Console\Input\InputInterface;
use Symfony\Component\Console\Input\InputOption;
use Symfony\Component\Console\Output\OutputInterface;

class DemoArgsCommand extends Command
{
    protected function configure()
    {
        $this
            ->setName('demo:args')
            ->setDescription('Describe args behaviors')
            ->setDefinition(
                new InputDefinition(array(
                    new InputOption('foo', 'f'),
                    new InputOption('bar', 'b', InputOption::VALUE_REQUIRED),
                    new InputOption('cat', 'c', InputOption::VALUE_OPTIONAL),
                ))
            );
    }

    protected function execute(InputInterface $input, OutputInterface $output)
    {
       // ...
    }
}

Since the foo option doesn’t accept a value, it will be either false (when it is not passed to the command) or true (when --foo was passed by the user). The value of the bar option (and its b shortcut respectively) is required. It can be separated from the option name either by spaces or = characters. The cat option (and its c shortcut) behaves similar except that it doesn’t require a value. Have a look at the following table to get an overview of the possible ways to pass options:

Input	foo	bar	cat
--bar=Hello	false	"Hello"	null
--bar Hello	false	"Hello"	null
-b=Hello	false	"Hello"	null
-b Hello	false	"Hello"	null
-bHello	false	"Hello"	null
-fcWorld -b Hello	true	"Hello"	"World"
-cfWorld -b Hello	false	"Hello"	"fWorld"
-cbWorld	false	null	"bWorld"

Things get a little bit more tricky when the command also accepts an optional argument:

// ...

new InputDefinition(array(
    // ...
    new InputArgument('arg', InputArgument::OPTIONAL),
));

You might have to use the special -- separator to separate options from arguments. Have a look at the fifth example in the following table where it is used to tell the command that World is the value for arg and not the value of the optional cat option:

Input	bar	cat	arg
--bar Hello	"Hello"	null	null
--bar Hello World	"Hello"	null	"World"
--bar "Hello World"	"Hello World"	null	null
--bar Hello --cat World	"Hello"	"World"	null
--bar Hello --cat -- World	"Hello"	null	"World"
-b Hello -c World	"Hello"	"World"	null