即使在Windows上的backgroud中运行命令后，PHP脚本仍卡在exec上

Question

I want a php script from which I can execute a program, and terminate it if it doesn't complete execution in 2 seconds. I am using Windows. I have tried the following code:

exec("start /B program.exe");
sleep(2);
exec('taskkill /F /IM "program.exe"');

This doesn't seem to work as script is stuck on the first exec statement as long as program.exe is not finished execution. I can't figure out how to do fix this issue.

Answer 1

Right, exec() will block until execution completes. This question has great answers for how to do an exec() with a timeout. I think this will probably work best for you. I'll post the code here for completeness (but I can't take any credit!):

/**
 * Execute a command and return it's output. Either wait until the command exits or the timeout has expired.
 *
 * @param string $cmd     Command to execute.
 * @param number $timeout Timeout in seconds.
 * @return string Output of the command.
 * @throws \Exception
 */
function exec_timeout($cmd, $timeout) {
  // File descriptors passed to the process.
  $descriptors = array(
    0 => array('pipe', 'r'),  // stdin
    1 => array('pipe', 'w'),  // stdout
    2 => array('pipe', 'w')   // stderr
  );

  // Start the process.
  $process = proc_open('exec ' . $cmd, $descriptors, $pipes);

  if (!is_resource($process)) {
    throw new \Exception('Could not execute process');
  }

  // Set the stdout stream to none-blocking.
  stream_set_blocking($pipes[1], 0);

  // Turn the timeout into microseconds.
  $timeout = $timeout * 1000000;

  // Output buffer.
  $buffer = '';

  // While we have time to wait.
  while ($timeout > 0) {
    $start = microtime(true);

    // Wait until we have output or the timer expired.
    $read  = array($pipes[1]);
    $other = array();
    stream_select($read, $other, $other, 0, $timeout);

    // Get the status of the process.
    // Do this before we read from the stream,
    // this way we can't lose the last bit of output if the process dies between these     functions.
    $status = proc_get_status($process);

    // Read the contents from the buffer.
    // This function will always return immediately as the stream is none-blocking.
    $buffer .= stream_get_contents($pipes[1]);

    if (!$status['running']) {
      // Break from this loop if the process exited before the timeout.
      break;
    }

    // Subtract the number of microseconds that we waited.
    $timeout -= (microtime(true) - $start) * 1000000;
  }

  // Check if there were any errors.
  $errors = stream_get_contents($pipes[2]);

  if (!empty($errors)) {
    throw new \Exception($errors);
  }

  // Kill the process in case the timeout expired and it's still running.
  // If the process already exited this won't do anything.
  proc_terminate($process, 9);

  // Close all streams.
  fclose($pipes[0]);
  fclose($pipes[1]);
  fclose($pipes[2]);

  proc_close($process);

  return $buffer;
}

Edit

The 'exec' part of the proc_open() probably won't work on Windows, but it's probably unnecessary.

Answer 2

Are you doing this with php cli (command line) ? Open a command prompt as administrator .
To not being blocked by waiting for the program close the process of opening the program .

php myscript.php

pclose(popen("start /B program.exe", "r"));
sleep(2);
exec('taskkill /F /IM program.exe');
exit(0);

Would also be fine to put the exec start into a separate script and fire this script using exec

Answer 3

The first comment of the exec() manual page shows a very simple example.