shell

Shell

Introduction

The Shell component provides the ability to run shell commands in a subprocess, in a non-blocking manner.

?> The Shell component serves as replacement for shell_exec(), exec(), system() functions.

!> The Shell component is not a replacement for amphp/process, or symfony/process.

Usage

use Psl\Shell;

$result = Shell\execute('echo', arguments: ['Hello, World!']); // Hello, World!

API

Functions

• [Shell\execute(string $command, list<string> $arguments = [], ?string $working_directory = null, array<string, string> $environment = [], bool $escape_arguments = true, ?float $timeout = null): string php]

  Execute an external program.

  • [$command php]: The command to execute.
  • [$arguments php]: The command arguments listed as separate entries.
  • [$working_directory php]: The initial working directory for the command.
  • [$environment php]: A dict with the environment variables for the command that will be run.
  • [$escape_arguments php]: If set to true ( default ), all [$arguments php] will be escaped using [Shell\escape_argument(...) php].
  • [$timeout php]: The timeout in seconds. If set to null, the timeout will be disabled.

  If the command returns a non-zero exit code, [Shell\Exception\FailedExecutionException php] will be thrown.
  If the command being run is suspicious ( e.g: contains NULL byte ), [Shell\Exception\PossibleAttackException php] will be thrown.
  If the [$working_directory php] doesn't exist, or unable to create a new process, [Shell\Exception\RuntimeException php] will be thrown.
  If the [$timeout php] is reached before being able to read the process stream, [Shell\Exception\TimeoutException php] will be thrown.
  

  use Psl\Shell;
  
  $result = Shell\execute('echo', arguments: ['Hello, World!'], timeout: 1.0); // Hello, World!

  [Shell\execute(...) php] waits for the underlying process output in a non-blocking manner, this means that while a process is running, the script will not block, and allows other I/O operations to be performed.

  This non-blocking nature is useful when you want to execute a lot of commands concurrently, and you don't want to block the script.

  use Psl\Async;
  use Psl\Shell;
  
  // execute `sleep 1` 4 times concurrently
  Async\concurrently([
    fn() => Shell\execute('sleep', arguments: ['1']),
    fn() => Shell\execute('sleep', arguments: ['1']),
    fn() => Shell\execute('sleep', arguments: ['1']),
    fn() => Shell\execute('sleep', arguments: ['1']),
  ]);

  All commands in the example above will be executed concurrently, and the script will finish in ~1 second.

  We can also set a timeout for the read operation, and if the process is still running after the timeout, [Shell\Exception\TimeoutException php] will be thrown.

  use Psl\Shell;
  
  try {
    Shell\execute('sleep', ['1'], timeout: 0.5);
  } catch (Shell\Exception\TimeoutException $e) {
    // The command timed out.
  }

• [Shell\escape_argument(string $argument): string php]

  Escape a command argument.

  This function should only be used in combination with [Shell\execute(...) php], as the escape format is specific to the [Shell\execute(...) php] function.

  • [$argument php]: The command argument to escape.

  use Psl\Shell;
  
  $arguments = [
    $bar, // intentionally not escaped
    Shell\escape_argument($baz),
    Shell\escape_argument($qux),
  ];
  
  $result = Shell\execute($foo, arguments: $arguments, escape_arguments: false);

Exceptions

• [final class Shell\Exception\FailedExecutionException implements Shell\Exception\ExceptionInterface extends Execption php]

  Thrown when the command returns a non-zero exit code.

  use Psl\Shell;
  
  try {
    Shell\execute('php', arguments: ['-r', 'exit(1);'], timeout: 1.0);
  } catch (Shell\Exception\FailedExecutionException $e) {
    $exit_code = $e->getCode();
    $stdout_content = $e->getOutput();
    $stderr_content = $e->getErrorOutput();
  
    // ... do something.
  }

• [final class Shell\Exception\PossibleAttackException implements Shell\Exception\ExceptionInterface extends Execption php]

  Thrown when the command being run is suspicious ( e.g: contains NULL byte ).

  use Psl\Shell;
  
  try {
    Shell\execute('echo', arguments: ["Hello, World!\0"]);
  } catch (Shell\Exception\PossibleAttackException $e) {
    // ... do something.
  }

• [final class Shell\Exception\RuntimeException implements Shell\Exception\ExceptionInterface extends Execption php]

  Thrown when the [$working_directory php] doesn't exist, or unable to create a new process.

  use Psl\Shell;
  
  try {
    Shell\execute('echo', arguments: ['Hello, World!'], working_directory: '/foo/bar');
  } catch (Shell\Exception\RuntimeException $e) {
    // ... do something.
  }

• [final class Shell\Exception\TimeoutException implements Shell\Exception\ExceptionInterface extends Execption` php]

  Thrown when the [$timeout php] is reached before being able to read the process stream.

  use Psl\Shell;
  
  try {
    Shell\execute('sleep', ['1'], timeout: 0.5);
  } catch (Shell\Exception\TimeoutException $e) {
    // ... do something.
  }