Get project directory on command symfony 3.4

Pretty sure this question has been asked many time but I'm too lazy to search for it. Plus Symfony has moved away from pulling parameters/services from the container to injecting them. So I am not sure if previous answers are up to date.

It is pretty easy.

namespace AppBundle\Command;

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

class ProjectDirCommand extends Command
{
    protected static $defaultName = 'app:project-dir';

    private $projectDir;

    public function __construct($projectDir)
    {
        $this->projectDir = $projectDir;
        parent::__construct();
    }
    protected function execute(InputInterface $input, OutputInterface $output)
    {
        $output->writeln('Project Dir ' . $this->projectDir);
    }
}

Because your project directory is a string, autowire will not know what value to inject. You can either explicitly define your command as a service and manually inject the value or you can use the bind capability:

# services.yml or services.yaml
services:
    _defaults:
        autowire: true
        autoconfigure: true
        public: false
        bind:
            $projectDir: '%kernel.project_dir%' # matches on constructor argument name

You can inject KernelInterface to the command just adding it to the constructor parameters and then get the project directory with $kernel->getProjectDir():

<?php

namespace App\Command;

use Symfony\Component\Console\Command\Command;
use Symfony\Component\HttpKernel\KernelInterface;
use Symfony\Component\Console\Input\InputInterface;
use Symfony\Component\Console\Output\OutputInterface;

class FooCommand extends Command
{
    protected $projectDir;

    public function __construct(KernelInterface $kernel)
    {
        parent::__construct();
        $this->projectDir = $kernel->getProjectDir();
    }

    protected function execute(InputInterface $input, OutputInterface $output): int
    {
        echo "This is the project directory: " . $this->projectDir;
        //...
    }
}

Well, I would say, inject the %kernel.project_dir% or %kernel.root_dir% parameters directly in your command. No need to make your command dependent on the Kernel service.

And by the way you can also make your Command extends Symfony\Bundle\FrameworkBundle\Command\ContainerAwareCommand which is an abstract class. So you can access the container within your command by just calling getContainer method.

But, I would not advice you to this actually. Better take benefit of autowiring or configure your service in a "yaml" way.