An event-driven, non-blocking shell for ReactPHP based on the Symfony Console Shell.

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v1.0 2014-03-24 02:23 UTC


Event-driven, non-blocking shell for ReactPHP.

Pecan (/pɪˈkɑːn/) provides a non-blocking alternative to the shell provided in the Symfony Console component. Additionally, Pecan includes a basic, framework-agnostic shell component called Drupe that can be used as the basis for building custom shells.



Pecan\Drupe is a standalone component for building event-driven console components. I like to think of it as Pecan without the Shell.

Pass an EventLoopInterface to start() listening for input.

$loop  = \React\EventLoop\Factory::create();
$shell = new \Pecan\Drupe();

// $shell->start() returns $loop to allow this chaining.

Drupe Events

  • running - The shell is running.
  • data - Data was received from STDIN.
  • error - Indicates an I/O problem.
  • close - The shell was closed.


Pecan\Shell extends Drupe to provide an event-driven wrapper for a standard Symfony\Component\Console\Application. It can be used as a drop-in replacement for Symfony\Component\Console\Shell.

Note: To maintain a Symfony Console-like workflow, calling $shell->run() on Pecan\Shell starts the EventLoop, so make sure it gets called last.

Shell Events

Shell emits the same events as Drupe.


Pecan\Readline provides an interface for reading line-by-line input from STDIN. This component is heavily inspired by, and strives for parity with the NodeJS Readline Component.

Readline Events

  • line - A line has been read from STDIN.
  • pause - Reading from the stream has been paused.
  • resume - Reading from the stream has resumed.
  • error - The input stream encountered an error.
  • close - Then input stream was closed.


Pecan\Console\Console provides a standard interface for working with STDOUT and STDERR. It is inspired heavily by the NodeJS Console Component and takes some functionality from the Symfony Console Component


The Output classes extend the base Console Output. StreamOutput wraps a single stream resource, while ConsoleOutput contains both the STDOUT and STDERR streams.

  • StreamOutputInterface
  • ConsoleOutputInterface
  • PecanOutput

Using Pecan

Using Drupe as a Standalone Shell

use Pecan\Drupe;

$loop   = \React\EventLoop\Factory::create();
$shell  = new Drupe();

// Example one-time callback to write the initial prompt.
// This resumes reading from STDIN and kicks off the shell.
$shell->once('running', function (Drupe $shell) {
    $shell->setPrompt('drupe> ')->prompt();

// Example callback for the data event.
// By convention, any call to write() will be followed by a call to prompt() 
// once the data has been written to the output stream.
$shell->on('data', function ($line, Drupe $shell) {

    $command = (!$line && strlen($line) == 0) ? false : rtrim($line);

    if ('exit' === $command || false === $command) {
    } else {
        $shell->writeln(sprintf(PHP_EOL.'// in: %s', $line));


// Example callback for the close event.
$shell->on('close', function ($code, Drupe $shell) {
        '// Goodbye.',
        sprintf('// Shell exits with code %d', $code),


Using Shell with Symfony Console Applications

Here is a shell that echoes back any input it receives, and then exits.

// Pecan\Shell wraps a standard Console Application.
use Symfony\Component\Console\Application;
use Pecan\Shell;

$shell = new Shell(new Application('pecan'));

$shell->on('data', function($line, Shell $shell) {
    $shell->write($line)->then(function($shell) {


Injecting An EventLoopInterface into Pecan\Shell

Unless you pass \Pecan\Shell an object implementing EventLoopInterface as its second constructor method, the Shell will get one from the EventLoop Factory. Keep this in mind if you want to integrate Pecan into an existing ReactPHP project.

use Symfony\Component\Console\Application;
use Pecan\Shell;

$loop  = \React\EventLoop\Factory::create();

// Do other things requiring $loop...

$shell = new Shell(new Application('pecan'), $loop);

// We must still let the shell run the EventLoop.

Example exit callback

// Example callback for the exit event.
$shell->on('exit', function($code, \Pecan\Shell $shell) {
    $shell->emit('output', [
            sprintf('// Shell exits with code %d', $code)