Tutorial :shell_exec() timeout management & exec()



Question:

I'm running a third party script by using a wrapper class I've written which calls shell_exec() and pipes into a file I parse later using php code. I should mention that this is working, but I am trying to enhance the functionality, having encountered a use case I hadn't thought of.

How is it best to manage timeout on shell_exec()? I was thinking of wrapping it in a try() catch() but I'm not sure how to best handle the time component.

I've been reading a few questions on here relating to shell_exec() and exec() and it seems that by passing output params to exec() you can get a return, but that does rely on the script finishing with a return status. Plus in my mini test page, I can't seem to get it to return any output!

The other option I thought about was using a modal dialog, with an ajax style spinner whilst the script it working, and setting a manual timeout in javascript. Which then gave the user a model dialog message about it failing/timeout and ending.

Are there any accepted methods for this use case?

My mini test, consisted of the following,

public $e_return = array();  public $e_status = '';  // Paths are absolute from /  public function execCheck($domain){      exec($this->ssl_check_path." -s ".$domain." -p 443 > ".$this->folder.$this->filename." 2>&1 &", &$this->e_return, &$this->e_status);  }    // Returns  Array  (  )    0  

Using this question as ref, Can't execute PHP script using PHP exec

http://www.php.net/manual/en/function.exec.php


Solution:1

I would suggest you look into using proc_open. You can configure it to return a stream resource, manually keep a timer, and if the timer expires before the process completes, you can terminate it with proc_terminate. If it does complete before the timer expires, then you can use proc_close then stream_get_contents to grab the data that would have otherwise been written to stdout.

See http://www.php.net/manual/en/function.proc-open.php


Solution:2

I write some working piece of code for such task. Function returns exit code (0 - OK, >0 - error) and writes stdout, stderr to reference variables.

/*execute program and write all output to $out  terminate program if it runs more than 30 seconds */  execute("program --option", null, $out, $out, 30);  echo $out;    function execute($cmd, $stdin=null, &$stdout, &$stderr, $timeout=false)  {      $pipes = array();      $process = proc_open(          $cmd,          array(array('pipe','r'),array('pipe','w'),array('pipe','w')),          $pipes      );      $start = time();      $stdout = '';      $stderr = '';        if(is_resource($process))      {          stream_set_blocking($pipes[0], 0);          stream_set_blocking($pipes[1], 0);          stream_set_blocking($pipes[2], 0);          fwrite($pipes[0], $stdin);          fclose($pipes[0]);      }        while(is_resource($process))      {          //echo ".";          $stdout .= stream_get_contents($pipes[1]);          $stderr .= stream_get_contents($pipes[2]);            if($timeout !== false && time() - $start > $timeout)          {              proc_terminate($process, 9);              return 1;          }            $status = proc_get_status($process);          if(!$status['running'])          {              fclose($pipes[1]);              fclose($pipes[2]);              proc_close($process);              return $status['exitcode'];          }            usleep(100000);      }        return 1;  }  


Solution:3

I tried with popen(), but there is no way to terminate the proccess afterwards. Also, stream_get_contents() blocks the stream even when using stream_set_blocking on Windows, so I had to use fread instead. Furthermore, proc_terminate doesn't work properly on Windows, so I had to use an alternative kill function.

I've came up with this, it should work both on Windows and Linux now:

function execute($command, $timeout = 5) {      $handle = proc_open($command, [['pipe', 'r'], ['pipe', 'w'], ['pipe', 'w']], $pipe);        $startTime = microtime(true);        /* Read the command output and kill it if the proccess surpassed the timeout */      while(!feof($pipe[1])) {          $read .= fread($pipe[1], 8192);          if($startTime + $timeout < microtime(true)) break;      }        kill(proc_get_status($handle)['pid']);      proc_close($handle);        return $read;  }    /* The proc_terminate() function doesn't end proccess properly on Windows */  function kill($pid) {      return strstr(PHP_OS, 'WIN') ? exec("taskkill /F /T /PID $pid") : exec("kill -9 $pid");  }  

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