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shell – Any equivalent to subprocess in PHP?

Posted by: admin July 12, 2020 Leave a comment

Questions:

In Java and Python, you have the ProcessBuilder or subprocess modules that let you easily start a process using unescaped strings e.g. ["ls", "some unescaped directory name"] – they also give you powerful tools like access to read from stdout, stderr. Is there any equivalent feature of PHP that is more intelligent and useful than just exec()?

How to&Answers:

The closest equivalent that gives you access to stdin, stdout, and stderr, with two-way communication, would be proc_open().

Here’s the example from the docs:

<?php
$descriptorspec = array(
   0 => array("pipe", "r"),  // stdin is a pipe that the child will read from
   1 => array("pipe", "w"),  // stdout is a pipe that the child will write to
   2 => array("file", "/tmp/error-output.txt", "a") // stderr is a file to write to
);

$cwd = '/tmp';
$env = array('some_option' => 'aeiou');

$process = proc_open('php', $descriptorspec, $pipes, $cwd, $env);

if (is_resource($process)) {
    // $pipes now looks like this:
    // 0 => writeable handle connected to child stdin
    // 1 => readable handle connected to child stdout
    // Any error output will be appended to /tmp/error-output.txt

    fwrite($pipes[0], '<?php print_r($_ENV); ?>');
    fclose($pipes[0]);

    echo stream_get_contents($pipes[1]);
    fclose($pipes[1]);

    // It is important that you close any pipes before calling
    // proc_close in order to avoid a deadlock
    $return_value = proc_close($process);

    echo "command returned $return_value\n";
}
?>

If you only need stdout and stdin, you can use popen().

This is my modified example, since the manual’s sucks:

<?php
$handle = popen('/path/to/executable', 'r');

$lines = [];
while (!feof($handle))
{
    $lines[] = fgets($handle);
}

pclose($handle);

This will read the output of /path/to/executable into an array of lines of output.

You also asked about escaping arguments. You can do that with escapeshellarg():

$escapedArg = escapeshellarg($arg);