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Request #81493 shell_exec() should get a `int &$result_code = null` argument
Submitted: 2021-10-01 13:52 UTC Modified: 2021-10-01 15:21 UTC
From: divinity76 at gmail dot com Assigned:
Status: Open Package: Unknown/Other Function
PHP Version: Next Minor Version OS:
Private report: No CVE-ID: None
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 [2021-10-01 13:52 UTC] divinity76 at gmail dot com
Description:
------------
doing exactly the same as the $result_code argument for system() and passthru() and exec()

Test script:
---------------
<?php
$result_code=null;
shell_exec(bin2hex(random_bytes(10))." 2>&1", $result_code);
var_dump($result_code);

Expected result:
----------------
platform-specific expected result, but at least on Linux one would expect:
int(127)

Actual result:
--------------
PHP Warning:  shell_exec() expects exactly 1 parameter, 2 given in /home/hansh/foo3.php on line 3
NULL


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 [2021-10-01 14:37 UTC] requinix@php.net
-Status: Open +Status: Feedback
 [2021-10-01 14:37 UTC] requinix@php.net
If you want a status code then why not use exec() or system()? Do we really need to make all three functions even *more* similar to each other?
 [2021-10-01 15:01 UTC] divinity76 at gmail dot com
-Status: Feedback +Status: Open
 [2021-10-01 15:01 UTC] divinity76 at gmail dot com
@requinix to use exec() for the same task as shell_exec(), you'll have to (ab)use implode() like

exec($cmd,$output,$ret);
$output=implode("\n", $output);

and to use system() for the same job, you'd have to (ab)use ob_* like

ob_start();
system($cmd,$ret);
$output=ob_get_clean();

same for passthru() 


as it stands now, if you want to do a shell_exec while also getting the os-level return value, you'll have to do a exec()+implode() workaround.. there would be no need for workarounds if shell_exec supported $result_code
 [2021-10-01 15:08 UTC] divinity76 at gmail dot com
actually the implode() workaround is non-binary-safe, take for example:

<?php
declare(strict_types=1);
$cmd= "php -r ".escapeshellarg('echo '.var_export("\n",true).";");
exec($cmd,$output,$ret);
$output=implode("\n",$output);
var_dump($output);

?>

it prints emptystring, not a string containing a newline, sooo data corruption
 [2021-10-01 15:17 UTC] divinity76 at gmail dot com
actually scratch the exec()  workaround, turns out that exec() is non-binary-safe and can't do shell_exec()'s job at all (in cases where binary safety is important) 

- with exec() it is impossible to differentiate between programs printing "foo" and "foo\n"
 [2021-10-01 15:21 UTC] nikic@php.net
The docs for shell_exec() say:

> On Windows, the underlying pipe is opened in text mode which can cause the function to fail for binary output. Consider to use popen() instead for such cases.

So it wouldn't be binary safe either...

It's funny how we have so many of these functions and they all kinda suck.
 [2021-10-01 15:44 UTC] divinity76 at gmail dot com
>It's funny how we have so many of these functions and they all kinda suck.

yeah... that reminds me, back in 2019 i made my own function to do this stuff, cus i didn't particularly like any of them (well, maybe except proc_open, but that one is kind-of too difficult to use, most of the time)

i know it's not particularly relevant to this feature request, but i'd love for someone to tell me what sucks about this function

<?php
/**
 * better version of shell_exec(),
 * supporting both stdin and stdout and stderr and os-level return code
 *
 * @param string $cmd
 *            command to execute
 * @param string $stdin
 *            (optional) data to send to stdin, binary data is supported.
 * @param string $stdout
 *            (optional) stdout data generated by cmd
 * @param string $stderr
 *            (optional) stderr data generated by cmd
 * @param bool $print_std
 *            (optional, default false) if you want stdout+stderr to be printed while it's running,
 *            set this to true. (useful for long-running commands)
 * @return int
 */
function hhb_exec(string $cmd, string $stdin = "", string &$stdout = null, string &$stderr = null, bool $print_std = false): int
{
    $stdouth = tmpfile();
    $stderrh = tmpfile();
    $descriptorspec = array(
        0 => array(
            "pipe",
            "rb"
        ), // stdin
        1 => array(
            "file",
            stream_get_meta_data($stdouth)['uri'],
            'ab'
        ),
        2 => array(
            "file",
            stream_get_meta_data($stderrh)['uri'],
            'ab'
        )
    );
    $pipes = array();
    $proc = proc_open($cmd, $descriptorspec, $pipes);
    while (strlen($stdin) > 0) {
        $written_now = fwrite($pipes[0], $stdin);
        if ($written_now < 1 || $written_now === strlen($stdin)) {
            // ... can add more error checking here
            break;
        }
        $stdin = substr($stdin, $written_now);
    }
    fclose($pipes[0]);
    unset($stdin, $pipes[0]);
    if (! $print_std) {
        $proc_ret = proc_close($proc); // this line will stall until the process has exited.
        $stdout = stream_get_contents($stdouth);
        $stderr = stream_get_contents($stderrh);
    } else {
        $stdout = "";
        $stderr = "";
        stream_set_blocking($stdouth, false);
        stream_set_blocking($stderrh, false);
        $fetchstd = function () use (&$stdout, &$stderr, &$stdouth, &$stderrh): bool {
            $ret = false;
            $tmp =  stream_get_contents($stdouth); // fread($stdouth, 1); //
            if (is_string($tmp) && strlen($tmp) > 0) {
                $ret = true;
                $stdout .= $tmp;
                fwrite(STDOUT, $tmp);
            }
            $tmp = stream_get_contents($stderrh);// fread($stderrh, 1); //
            // var_dump($tmp);
            if (is_string($tmp) && strlen($tmp) > 0) {
                $ret = true;
                $stderr .= $tmp;
                fwrite(STDERR, $tmp);
            }
            return $ret;
        };
        while (($status = proc_get_status($proc))["running"]) {
            if (! $fetchstd()) {
                // 100 ms
                usleep(100 * 1000);
            }
        }
        $proc_ret = $status["exitcode"];
        proc_close($proc);
        $fetchstd();
    }
    fclose($stdouth);
    fclose($stderrh);
    return $proc_ret;
}

?>
 
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