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Bug #35131 stream_select() in conjuntion with popen() does not appear to work
Submitted: 2005-11-06 22:07 UTC Modified: 2008-03-16 01:00 UTC
Votes:3
Avg. Score:4.0 ± 0.8
Reproduced:3 of 3 (100.0%)
Same Version:3 (100.0%)
Same OS:1 (33.3%)
From: larryjadams at comcast dot net Assigned:
Status: No Feedback Package: Streams related
PHP Version: 5CVS-2007-07-17 OS: WindowsXP Pro SP2
Private report: No CVE-ID: None
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 [2005-11-06 22:07 UTC] larryjadams at comcast dot net
Description:
------------
If I call $my_fd = popen("mycommand", "rb"); to a function that hangs/suspends and then subsquently call:

stream_select(...) using $read=array($my_fd) with a timeout, the steam_select returns immediately, event if I have set $my_fd as blocking using stream_set_blocking();

I would like stream_select to wait on output from the pipe prior to firing, or to drive a timeout.

Thanks,

Larry Adams
The Cacti Group

Reproduce code:
---------------
if (function_exists("stream_select")) {
  if ($config["cacti_server_os"] == "unix")  {
    $fp = popen($command, "r");
  }else{
    $fp = popen($command, "rb");
  }

  /* set script server timeout */
  $script_timeout = read_config_option("script_timeout");

  /* establish timeout variables */
  $to_sec = floor($script_timeout/1000);
  $to_usec = ($script_timeout%1000)*1000;

  /* Prepare the read array */
  $read = array($fp);

  stream_set_blocking ($fp, 1);
  if (false === ($num_changed_streams = stream_select($read, $write = NULL, $except = NULL, $to_sec, $to_usec))) {
    cacti_log("WARNING: SERVER POPEN Timed out.");
    $output = "U";
  }elseif ($num_changed_streams > 0) {
    $output = fgets($fp, 4096);
  }

  pclose($fp);
}else{
  $output = `$command`;
}

$command = a file with the following:

<?php sleep(20); echo "Hello:20.00\n"; ?>

The stream_select timeout is 5 seconds.


Expected result:
----------------
popen will be called, stream_select will block until timeout has expired, the number of fd's changed will be 0 and my result will be as expected.

Actual result:
--------------
stream_select returns immediately.

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 [2007-07-18 13:53 UTC] larryjadams at comcast dot net
The set block option now works.  However, the stream select still waits for the script to return or for ever, whichever comes first :).  Here is the revised code.  Simply place test1.php and test2.php in the c:\ directory.

test1.php
<?php
$command = "php -q c:/test2.php";

if (function_exists("stream_select")) {
	$fp = popen($command, "rb");

	/* set script server timeout in milliseconds */
	$script_timeout = 5000;

	/* establish timeout variables */
	$to_sec = floor($script_timeout/1000);
	$to_usec = ($script_timeout%1000)*1000;

	/* Prepare the read array */
	$read = array($fp);

	stream_set_blocking ($fp, 1);
	if (false === ($num_changed_streams = stream_select($read, $write = NULL, $except = NULL, $to_sec, $to_usec))) {
		echo "WARNING: SERVER POPEN Timed out.\n";
		$output = "U";
	}elseif ($num_changed_streams > 0) {
		$output = fgets($fp, 4096);
		echo "Command Exited with a Result of '" . trim($output) . "'\n";
	}

	pclose($fp);
}else{
	$output = `$command`;
}
?>

test2.php
<?php sleep(20);echo "Ehllo\n"; ?>

TheWitness
 [2007-07-18 14:59 UTC] jani@php.net
I didn't try it on Windows myself, I'll test this later on *nix.
 [2008-01-26 01:10 UTC] jani@php.net
I have no interest in fixing Windows bugs, there's enough work with the real OSes.
 [2008-03-16 01:00 UTC] php-bugs at lists dot php dot net
No feedback was provided for this bug for over a week, so it is
being suspended automatically. If you are able to provide the
information that was originally requested, please do so and change
the status of the bug back to "Open".
 
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