.. index:: single: Process single: Components; Process
The Process component executes commands in sub-processes.
$ composer require symfony/process
The :class:`Symfony\\Component\\Process\\Process` class executes a command in a sub-process, taking care of the differences between operating system and escaping arguments to prevent security issues. It replaces PHP functions like :phpfunction:`exec`, :phpfunction:`passthru`, :phpfunction:`shell_exec` and :phpfunction:`system`:
use Symfony\Component\Process\Exception\ProcessFailedException; use Symfony\Component\Process\Process; $process = new Process(['ls', '-lsa']); $process->run(); // executes after the command finishes if (!$process->isSuccessful()) { throw new ProcessFailedException($process); } echo $process->getOutput();
The getOutput()
method always returns the whole content of the standard
output of the command and getErrorOutput()
the content of the error
output. Alternatively, the :method:`Symfony\\Component\\Process\\Process::getIncrementalOutput`
and :method:`Symfony\\Component\\Process\\Process::getIncrementalErrorOutput`
methods return the new output since the last call.
The :method:`Symfony\\Component\\Process\\Process::clearOutput` method clears the contents of the output and :method:`Symfony\\Component\\Process\\Process::clearErrorOutput` clears the contents of the error output.
You can also use the :class:`Symfony\\Component\\Process\\Process` class with the for each construct to get the output while it is generated. By default, the loop waits for new output before going to the next iteration:
$process = new Process(['ls', '-lsa']); $process->start(); foreach ($process as $type => $data) { if ($process::OUT === $type) { echo "\nRead from stdout: ".$data; } else { // $process::ERR === $type echo "\nRead from stderr: ".$data; } }
Tip
The Process component internally uses a PHP iterator to get the output while
it is generated. That iterator is exposed via the getIterator()
method
to allow customizing its behavior:
$process = new Process(['ls', '-lsa']); $process->start(); $iterator = $process->getIterator($process::ITER_SKIP_ERR | $process::ITER_KEEP_OUTPUT); foreach ($iterator as $data) { echo $data."\n"; }
The mustRun()
method is identical to run()
, except that it will throw
a :class:`Symfony\\Component\\Process\\Exception\\ProcessFailedException`
if the process couldn't be executed successfully (i.e. the process exited
with a non-zero code):
use Symfony\Component\Process\Exception\ProcessFailedException; use Symfony\Component\Process\Process; $process = new Process(['ls', '-lsa']); try { $process->mustRun(); echo $process->getOutput(); } catch (ProcessFailedException $exception) { echo $exception->getMessage(); }
Tip
You can get the last output time in seconds by using the
:method:`Symfony\\Component\\Process\\Process::getLastOutputTime` method.
This method returns null
if the process wasn't started!
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 while they run):
$process = new Process(['/path/command', '--option', 'argument', 'etc.']); $process = new Process(['/path/to/php', '--define', 'memory_limit=1024M', '/path/to/script.php']);
If you need to use stream redirections, conditional execution, or any other feature provided by the shell of your operating system, you can also define commands as strings using the :method:`Symfony\\Component\\Process\\Process::fromShellCommandline` static factory.
Each operating system provides a different syntax for their command-lines, so it becomes your responsibility to deal with escaping and portability.
When using strings to define commands, variable arguments are passed as
environment variables using the second argument of the run()
,
mustRun()
or start()
methods. Referencing them is also OS-dependent:
// On Unix-like OSes (Linux, macOS) $process = Process::fromShellCommandline('echo "$MESSAGE"'); // On Windows $process = Process::fromShellCommandline('echo "!MESSAGE!"'); // On both Unix-like and Windows $process->run(null, ['MESSAGE' => 'Something to output']);
If you prefer to create portable commands that are independent from the operating system, you can write the above command as follows:
// works the same on Windows , Linux and macOS $process = Process::fromShellCommandline('echo "${:MESSAGE}"');
Portable commands require using a syntax that is specific to the component: when
enclosing a variable name into "${:
and }"
exactly, the process object
will replace it with its escaped value, or will fail if the variable is not
found in the list of environment variables attached to the command.
The constructor of the :class:`Symfony\\Component\\Process\\Process` class and
all of its methods related to executing processes (run()
, mustRun()
,
start()
, etc.) allow passing an array of environment variables to set while
running the process:
$process = new Process(['...'], null, ['ENV_VAR_NAME' => 'value']); $process = Process::fromShellCommandline('...', null, ['ENV_VAR_NAME' => 'value']); $process->run(null, ['ENV_VAR_NAME' => 'value']);
In addition to the env vars passed explicitly, processes inherit all the env
vars defined in your system. You can prevent this by setting to false
the
env vars you want to remove:
$process = new Process(['...'], null, [ 'APP_ENV' => false, 'SYMFONY_DOTENV_VARS' => false, ]);
When executing a long running command (like rsync
to a remote
server), you can give feedback to the end user in real-time by passing an
anonymous function to the
:method:`Symfony\\Component\\Process\\Process::run` method:
use Symfony\Component\Process\Process; $process = new Process(['ls', '-lsa']); $process->run(function ($type, $buffer) { if (Process::ERR === $type) { echo 'ERR > '.$buffer; } else { echo 'OUT > '.$buffer; } });
Note
This feature won't work as expected in servers using PHP output buffering. In those cases, either disable the output_buffering PHP option or use the :phpfunction:`ob_flush` PHP function to force sending the output buffer.
You can also start the subprocess and then let it run asynchronously, retrieving output and the status in your main process whenever you need it. Use the :method:`Symfony\\Component\\Process\\Process::start` method to start an asynchronous process, the :method:`Symfony\\Component\\Process\\Process::isRunning` method to check if the process is done and the :method:`Symfony\\Component\\Process\\Process::getOutput` method to get the output:
$process = new Process(['ls', '-lsa']); $process->start(); while ($process->isRunning()) { // waiting for process to finish } echo $process->getOutput();
You can also wait for a process to end if you started it asynchronously and are done doing other stuff:
$process = new Process(['ls', '-lsa']); $process->start(); // ... do other things $process->wait(); // ... do things after the process has finished
Note
The :method:`Symfony\\Component\\Process\\Process::wait` method is blocking, which means that your code will halt at this line until the external process is completed.
Note
If a Response
is sent before a child process had a chance to complete,
the server process will be killed (depending on your OS). It means that
your task will be stopped right away. Running an asynchronous process
is not the same as running a process that survives its parent process.
If you want your process to survive the request/response cycle, you can
take advantage of the kernel.terminate
event, and run your command
synchronously inside this event. Be aware that kernel.terminate
is called only if you use PHP-FPM.
Caution!
Beware also that if you do that, the said PHP-FPM process will not be available to serve any new request until the subprocess is finished. This means you can quickly block your FPM pool if you're not careful enough. That is why it's generally way better not to do any fancy things even after the request is sent, but to use a job queue instead.
:method:`Symfony\\Component\\Process\\Process::wait` takes one optional argument: a callback that is called repeatedly whilst the process is still running, passing in the output and its type:
$process = new Process(['ls', '-lsa']); $process->start(); $process->wait(function ($type, $buffer) { if (Process::ERR === $type) { echo 'ERR > '.$buffer; } else { echo 'OUT > '.$buffer; } });
Instead of waiting until the process has finished, you can use the :method:`Symfony\\Component\\Process\\Process::waitUntil` method to keep or stop waiting based on some PHP logic. The following example starts a long running process and checks its output to wait until its fully initialized:
$process = new Process(['/usr/bin/php', 'slow-starting-server.php']); $process->start(); // ... do other things // waits until the given anonymous function returns true $process->waitUntil(function ($type, $output) { return $output === 'Ready. Waiting for commands...'; }); // ... do things after the process is ready
Before a process is started, you can specify its standard input using either the
:method:`Symfony\\Component\\Process\\Process::setInput` method or the 4th argument
of the constructor. The provided input can be a string, a stream resource or a
Traversable
object:
$process = new Process(['cat']); $process->setInput('foobar'); $process->run();
When this input is fully written to the subprocess standard input, the corresponding pipe is closed.
In order to write to a subprocess standard input while it is running, the component provides the :class:`Symfony\\Component\\Process\\InputStream` class:
$input = new InputStream(); $input->write('foo'); $process = new Process(['cat']); $process->setInput($input); $process->start(); // ... read process output or do other things $input->write('bar'); $input->close(); $process->wait(); // will echo: foobar echo $process->getOutput();
The :method:`Symfony\\Component\\Process\\InputStream::write` method accepts scalars,
stream resources or Traversable
objects as argument. As shown in the above example,
you need to explicitly call the :method:`Symfony\\Component\\Process\\InputStream::close`
method when you are done writing to the standard input of the subprocess.
The input of a process can also be defined using PHP streams:
$stream = fopen('php:https://temporary', 'w+'); $process = new Process(['cat']); $process->setInput($stream); $process->start(); fwrite($stream, 'foo'); // ... read process output or do other things fwrite($stream, 'bar'); fclose($stream); $process->wait(); // will echo: 'foobar' echo $process->getOutput();
Any asynchronous process can be stopped at any time with the
:method:`Symfony\\Component\\Process\\Process::stop` method. This method takes
two arguments: a timeout and a signal. Once the timeout is reached, the signal
is sent to the running process. The default signal sent to a process is SIGKILL
.
Please read the :ref:`signal documentation below<reference-process-signal>`
to find out more about signal handling in the Process component:
$process = new Process(['ls', '-lsa']); $process->start(); // ... do other things $process->stop(3, SIGINT);
If you want to execute some PHP code in isolation, use the PhpProcess
instead:
use Symfony\Component\Process\PhpProcess; $process = new PhpProcess(<<<EOF <?= 'Hello World' ?> EOF ); $process->run();
You can run the process by using a a prepared command line using the double bracket notation. You can use a placeholder in order to have a process that can only be changed with the values and without changing the PHP code:
use Symfony\Component\Process\Process; $process = Process::fromShellCommandline('echo "$name"'); $process->run(null, ['name' => 'Elsa']);
Caution!
A prepared command line will not be escaped automatically!
By default processes have a timeout of 60 seconds, but you can change it passing
a different timeout (in seconds) to the setTimeout()
method:
use Symfony\Component\Process\Process; $process = new Process(['ls', '-lsa']); $process->setTimeout(3600); $process->run();
If the timeout is reached, a :class:`Symfony\\Component\\Process\\Exception\\ProcessTimedOutException` is thrown.
For long running commands, it is your responsibility to perform the timeout check regularly:
$process->setTimeout(3600); $process->start(); while ($condition) { // ... // check if the timeout is reached $process->checkTimeout(); usleep(200000); }
Tip
You can get the process start time using the getStartTime()
method.
.. versionadded:: 5.1 The ``getStartTime()`` method was introduced in Symfony 5.1.
In contrast to the timeout of the previous paragraph, the idle timeout only considers the time since the last output was produced by the process:
use Symfony\Component\Process\Process; $process = new Process(['something-with-variable-runtime']); $process->setTimeout(3600); $process->setIdleTimeout(60); $process->run();
In the case above, a process is considered timed out, when either the total runtime exceeds 3600 seconds, or the process does not produce any output for 60 seconds.
When running a program asynchronously, you can send it POSIX signals with the :method:`Symfony\\Component\\Process\\Process::signal` method:
use Symfony\Component\Process\Process; $process = new Process(['find', '/', '-name', 'rabbit']); $process->start(); // will send a SIGKILL to the process $process->signal(SIGKILL);
You can access the pid of a running process with the :method:`Symfony\\Component\\Process\\Process::getPid` method:
use Symfony\Component\Process\Process; $process = new Process(['/usr/bin/php', 'worker.php']); $process->start(); $pid = $process->getPid();
As standard output and error output are always fetched from the underlying process, it might be convenient to disable output in some cases to save memory. Use :method:`Symfony\\Component\\Process\\Process::disableOutput` and :method:`Symfony\\Component\\Process\\Process::enableOutput` to toggle this feature:
use Symfony\Component\Process\Process; $process = new Process(['/usr/bin/php', 'worker.php']); $process->disableOutput(); $process->run();
Caution!
You cannot enable or disable the output while the process is running.
If you disable the output, you cannot access getOutput()
,
getIncrementalOutput()
, getErrorOutput()
, getIncrementalErrorOutput()
or
setIdleTimeout()
.
However, it is possible to pass a callback to the start
, run
or mustRun
methods to handle process output in a streaming fashion.
This component also provides a utility class called :class:`Symfony\\Component\\Process\\PhpExecutableFinder` which returns the absolute path of the executable PHP binary available on your server:
use Symfony\Component\Process\PhpExecutableFinder; $phpBinaryFinder = new PhpExecutableFinder(); $phpBinaryPath = $phpBinaryFinder->find(); // $phpBinaryPath = '/usr/local/bin/php' (the result will be different on your computer)
Another utility provided by this component is a method called :method:`Symfony\\Component\\Process\\Process::isTtySupported` which returns whether TTY is supported on the current operating system:
use Symfony\Component\Process\Process; $process = (new Process())->setTty(Process::isTtySupported());