Dumps container, referenceContainer, block and referenceBlock names and locations from Magento2 site.

refcontainer.php

<?php

$instructions = array("container", "referenceContainer", "block", "referenceBlock");
foreach ($instructions as $instruction) {
  $containers = array();

  $fp = fopen('debug_'.$instruction.'.txt', 'w');
  
  $command = 'egrep -r -i --include \*.xml "<'.$instruction.'".*?"name=" *';
  exec($command, $output);

  $container_max_length = 1;
  $pattern = '/(.*?):.*<'.$instruction.'.*name="(.*?)".*/';
  foreach ($output as $subject) {
    preg_match($pattern, $subject, $matches);
    $containers[$matches[2]][] = $matches[1];
    if (strlen($matches[2]) > $container_max_length) $container_max_length = strlen($matches[2]);
  }

  $n=1;

  ksort($containers);
  foreach ($containers as $k => $v) {
    fprintf($fp, "%6s", "$n. ");
    fprintf($fp, "%-".$container_max_length."s".$v[0]."\n", $k);
    $i=1;
    while (isset($v[$i])) {
      fprintf($fp, "      %-".$container_max_length."s".$v[$i]."\n", "");
      $i++;
    }
    $n++;
  }

  fclose($fp);
}

?>

I can't really take credit for this, found it on Stack Overflow shared by maxagaz and just modified it to dump them all to txt file.