Checking if process still running?

Question

As a way to build a poor-man\'s watchdog and make sure an application is restarted in case it crashes (until I figure out why), I need to write a PHP CLI script that will be

Answer 1

To check whether process is running by its name, you can use pgrep, e.g.

$is_running = shell_exec("pgrep -f lighttpd");

or:

exec("pgrep lighttpd", $output, $return);
if ($return == 0) {
    echo "Ok, process is running\n";
}

as per this post.

If you know the PID of the process, you can use one the following functions:

  /**
   * Checks whether the process is running.
   *
   * @param int $pid Process PID.
   * @return bool
   */
  public static function isProcessRunning($pid) {
    // Calling with 0 kill signal will return true if process is running.
    return posix_kill((int) $pid, 0);
  }

  /**
   * Get the command of the process.
   * For example apache2 in case that's the Apache process.
   *
   * @param int $pid Process PID.
   * @return string
   */
  public static function getProcessCommand($pid) {
    $pid = (int) $pid;
    return trim(shell_exec("ps o comm= $pid"));
  }

Related: How to check whether specified PID is currently running without invoking ps from PHP?