..tip::

..versionadded::3.3

The ability to define commands as array of arguments was introduced in Symfony 3.3.

The ability to define commands as arrays of arguments was introduced in

Symfony 3.3.

When defining commands as arrays, its arguments are escaped for you and you should not

escape them any further. You can also define commands as strings. When doing so, the

command-line is parsed by the underlying shell of your operating system. This allows

using e.g. stream redirections or conditional execution, but this is a lot less portable

since each OS (esp. Windows vs Unix-like) handles escaping and parsing differently.

When passing a command-line string, it becomes your responsibility to deal with this.

Using array of arguments is the recommended way to define commands. This

saves you from any escaping and allows sending signals seamlessly

(e.g. to stop processes before completion.)::

If you needto define commands as strings, variable arguments should be passed as

environment variables using thesecond argumentofthe ``run()``, ``mustRun()`` or

``start()`` methods. Referencing them in command-linestrings is OS-dependent::

If you needuse stream redirections, conditional execution, or any other

features provided by theshellofyour operating system, you can also define

commands asstrings.

Please note that each OS provides a different syntax for their command-lines

so that it becomes your responsibility to deal with escaping and portability.

To provide any variable arguments to command-line string, pass them as

environment variables using the second argument of the ``run()``,

``mustRun()`` or ``start()`` methods. Referencing them is also OS-dependent::

Getting real-time Process Output