Combine find, xargs and sed.

find . -name "*.css" | xargs sed -i 's/BEFORE/AFTER/g'

Define a function echo_count and count the function name to be called in the script. You can refer to a variable ${TOTAL} .For example,

#!/bin/bash

export TARGET_DIR='./' # Current directory
export ORIGINAL_NAME='xxxxx'
export TARGET_NAME='yyyyy'

find "${TARGET_DIR}" -name '*${ORIGINAL_NAME}*' -execdir rename "s/${ORIGINAL_NAME}/${TARGET_NAME}/g" '{}' \;

\Drupal::request()->getHost()

This one doesn't include the URL that begins with https://〜, therefore you may want to write it as follows:

$hostname = sprintf('https://%s/', \Drupal::request()->getHost());

For example shown below, ['data'] requires after ['active'] like ['active']['data'].

Drupal 8 provides a useful helper funciton $entity->toLink(..). You must return it by converting to a string by using ->toString() at the end.

public function foo(Request $request = NULL) {

  $id = $request->get('id');  // from query string
  $entity = YourEntity::load($id);

  $message = $this->t('Check at @url.', [
    '@url' => $entity->toLink('<TEXT_TO_LINK_HERE>', 'edit-form')->toString(),
  ]);

  return [
    '#type' => 'markup',
    '#markup' => $message, 
  ];
}

You can output the current date and time as follows:

print \Drupal::service('date.formatter')->format((new \DateTime())->getTimeStamp(), 'short');

You cannot download a private key. You can only download the Server certs.

aws acm get-certificate --region us-east-1 --certificate-arn arn:aws:acm:us-east-1:123456789012:certificate/12345678-1234-1234-1234-123456789012

You can get the JSON output that contains the server and intermediate certs as follows:

Call the following static method\Drupal::service('uuid')->generate()

$uuid = \Drupal::service('uuid')->generate();

Put an Email address into $email that needs to be validated.

\Drupal::service('email.validator')->isValid($email);