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If I have a Python script I started in PHP from a web server, how do I stop it? – Apache

I have an Apache Web server on my RaspberryPi 4 that has a program written in Python on it that will turn on an 8×8 matrix of red led’s. I have a HTML and PHP page on the web server so I can remotely execute that script. The HTML is just 2 buttons and on the press of the button it goes to this PHP program: 

<?php

  ini_set('display_errors', 1);
  ini_set('display_startup_errors', 1);
  error_reporting(E_ALL);

  if ($_SERVER['REQUEST_METHOD'] == "POST" and isset($_POST['on']))
  {
    lightOn();
  } elseif ($_SERVER['REQUEST_METHOD'] == "POST" and isset($_POST['off']))
  {
    lightOff();
  }

  function lightOn()
  {
    $command = escapeshellcmd('sudo python3 led_display.py');
    $output = shell_exec($command);

    header('Location: index.html');
    exit;

  }

  function lightOff()
  {
    $command = escapeshellcmd('');
    $output = shell_exec($command);

    header('Location: index.html');
    exit;
  }

?>

This PHP program just recognizes which of the 2 buttons was pressed and on the press executes a function. For the lightOn() function it is simple as I just execute the script that drives the 8×8 led matrix. However I want the user to be able to stop the script at any time by pressing the other button. On a normal command line interface I would type ‘Control + c’ to stop any running script. How would I achieve that in PHP through shell_exec, or any other method?

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2

Answers


  1. 0

    In your server, find out what’s the process id (PID) via ps, top or even htop commands. Than you can kill it with the command kill {pid_number}.

    Something like:

    $ ps aux | grep led_display # the first number that appears is the PID. let's assume it's 1234
$ kill 1234
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  2. 0

    Assuming that you have control over the sudoers file and know how to make it so your web-server process can execute the command referenced in lightOff without a password you should be able to do

    $command = escapeshellcmd('sudo pkill -TERM led_display.py');

    Of course that would terminate ANY process called led_display.py, not just the one you started from the web-server process.

    EDIT:

    What happens if you background the process?

    $command = escapeshellcmd('sudo python3 led_display.py > /dev/null 2>&1 &');
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