Find all files in a directory /path/to/directory and its sub-directories recursively:

find /path/to/directory/ -size 0 -type f

or

find /path/to/directory/ -size 0 -type f -print

Extend:

If you have been read Some basic drush commands, you can use Drush by running drush cr command line. However, this way is not useful when you're in the development process because you need to run the command line every time you change the code.

I'll guide you follow 2 ways:

I will guide you to install Drupal Console with global access permission on your personal computer in 4 steps.

The steps to install Drupal Console is similar to the steps to install Drush 8:

Step 1: Download the latest version of drupal.phar

curl https://drupalconsole.com/installer -L -o drupal.phar

Step 2: Check by running this command line:

php drupal.phar

If everything is fine, you can see the message like the below image:

Following these below steps to install Drush 8 (Ubuntu and MacOS):

The current version of Drush 8 when I writing this article is 8.2.1

1. Choose the latest version of Drush 8 in the below link: 

https://github.com/drush-ops/drush/releases

You can choose v8.2.2 and download the drush.phar. You can use the bellow command line to download it:

wget https://github.com/drush-ops/drush/releases/download/8.2.1/drush.phar

Note: to use the wget command line, you need to install it first.

Sometimes in the development process, you need to debug to define the values or to find the errors. Debugging is very important for any developers.

1. Change permission of all files:

find /<path_to_desired_directory> -type f -print0 | xargs -0 chmod 0755

2. Change permission of all folder:

find /<path_to_desired_directory> -type d -print0 | xargs -0 chmod 0644

Drush is a supporting tool, which is important for any Drupal developers. It helps executing a task with many steps simpler through one command. It's also really helpful in deployment process through integrating it in script.

I will share some basic Drush commands that I usually use:

1. Clear cache / Cache rebuild.

For Drupal 7

drush cc all

For Drupal 8/9

drush cr

2. Delete all tables in the database (available on Drupal 7/8/9).

When I searched a solution for connecting through VPN with L2TP/IPSec on Ubuntu (I used Ubuntu 18.04 at this time), I found this article and kept it in my note.

Just as a followup to the great information you provided, thought I'd give people a complete set of steps I took to get this working on Ubuntu GNOME 17.04: