$uid = \Drupal::currentUser()->id() // if you wan to get a username of the current user
$account = \Drupal\user\Entity\User::load($uid); // pass your uid
$username = $account->getUsername();

You can install Zend Framework v2 as follows:
composer require zendframework/zendframework

However Zend Framework v1 has already been obsolete, therefore when you want to install it manually, you need to download the library from GitHub, and copy (move) to your application directory.

Download Zend Framework v1 library from GitHub (Note that the following example is aimed for minimal package. If you want to install the full package, delete a -minimal portion. Also note that the following command line is just one line, even though it has new lines.)

If you want to create a module that provides your custom block(s) in Drupal 8, for instance, you can only write two source codes such as my_custom_block.info.yml and MyCustomBlock.php. However how can you make custom configuration fields on your custom block translatable? The answer is to add one additional file my_custom_block.yml as a schema file.

AWS announced to provide their own internal NTP inside VPC at AWS re:Invent 2017. Here is how to do it:
CentOS
sudo yum erase ntp*; sudo yum -y install chrony; sudo service chronyd start

Debian/Ubuntu
sudo apt-get remove -y ntp*; sudo apt-get -y install chrony; sudo service chronyd start; apt-get autoremove

Add an option -o StrictHostKeyChecking=no into a ssh command:
ssh -o StrictHostKeyChecking=no your_username@example.com

OR
export TARGET_HOST='example.com'

if [ -z `ssh-keygen -F ${TARGET_HOST}` ]; then
ssh-keyscan -H ${TARGET_HOST} >> ~/.ssh/known_hosts
fi

ssh-keygen -R ${TARGET_HOST}
ssh-keyscan -f ~/.ssh/known_hosts ${TARGET_HOST} >>~/.ssh/known_hosts 2>/dev/null

Create a file for swap
======================

Create a file named /swapfile for 4GB size (e.g. Create a file called swapfile under root (/))
$ dd if=/dev/zero of=/swapfile bs=1024K count=4096

Format the swapfile with a mkswap command
======================================

$ mkswap /swapfile

Confirm the current swap file status
==========================

pi@raspberrypi ~ $ swapon -s

Filename Type Size Used Priority
/var/swap file 102396 0 -1

Specification - What I want to do
=================================
I would like to input in-out records at my company automagically by using Raspberry PI and detecting my iPhone's bluetooth signal. That is, I want to make bluetooth proximity checker with my Raspberry PI. The specification is:

Detect Bluetooth signal by Raspberry PI
When I come into my office, the system records the time to come into the office
When I leave from my office, the system records the time to leave out from the office
Integrate Google Sheet to record the time

That is only what I want to do. Think about the spending time to input the in/out time manually. We can reduce our precious 12-20 total hours through a year (Assuming 3-5 min per a day and 240 working days through a year in order to input the records). It can be converted to a half or a day.
Then, OK, Let's see how we can make it!

HTTP/2 has been supported since Apache 2.4.17. I tried sudo a2enmod http2 on this Ubuntu 16.04 host, however it said ERROR: Module http2 does not exist!. Looks I needed to upgrade Apache2 as follows:
sudo add-apt-repository -y ppa:ondrej/apache2
sudo apt-key update
sudo apt-get update
sudo apt-get --only-upgrade install apache2 -y

Select Y (Note that this will overwrite your current configuration; therefore do backup of apache2.conf if necessary.
*** apache2.conf (Y/I/N/O/D/Z) [default=N] ?

#!/bin/sh

export DATE_CURRENT=`date +%Y-%m-%d`
export TIME_CURRENT=`date +%Y%m%d%H%M%S`
export PURGE_AFTER_DAYS=30
export PURGE_AFTER=`date -d +${PURGE_AFTER_DAYS}days -u +%Y-%m-%d`
export BACKUP_TAG='backup'

# 1-1 Get the list of instances that you want to get backup
INSTANCES=`aws ec2 describe-tags --filters "Name=resource-type,Values=instance" "Name=key,Values=${BACKUP_TAG}" | awk '{print $3}'`

for INSTANCE in ${INSTANCES}; do

BACKUP=`aws ec2 describe-tags --filters "Name=resource-type,Values=instance" "Name=resource-id,Values=${INSTANCE}" "Name=key,Values=${BACKUP_TAG}" | awk '{print $5}'`

# 1-2 Check if the instance is marked as backup or not
if [ "${BACKUP}" == "true" ]; then

# 1-3 Create a backup
AMI_ID=`aws ec2 create-image --instance-id ${INSTANCE} --name "${INSTANCE}_${TIME_CURRENT}" --no-reboot`

# 1-4 Create a tag for search for later use
aws ec2 create-tags --resources ${AMI_ID} --tags Key=PurgeAllow,Value=true Key=PurgeAfter,Value=$PURGE_AFTER
fi
done

# 2-1 Search backups by tag
AMI_PURGE_ALLOWED=`aws ec2 describe-tags --filters "Name=resource-type,Values=image" "Name=key,Values=PurgeAllow" | awk '{print $3}'`

for AMI_ID in ${AMI_PURGE_ALLOWED}; do
PURGE_AFTER_DATE=`aws ec2 describe-tags --filters "Name=resource-type,Values=image" "Name=resource-id,Values=${AMI_ID}" "Name=key,Values=PurgeAfter" | awk '{print $5}'`

if [ -n ${PURGE_AFTER_DATE} ]; then
DATE_CURRENT_EPOCH=`date -d ${DATE_CURRENT} +%s`
PURGE_AFTER_DATE_EPOCH=`date -d ${PURGE_AFTER_DATE} +%s`

if [[ ${PURGE_AFTER_DATE_EPOCH} < ${DATE_CURRENT_EPOCH} ]]; then
# 2-2 Delete backup if it is marked as backup
aws ec2 deregister-image --image-id ${AMI_ID}

SNAPSHOT_ID=`aws ec2 describe-images --image-ids ${AMI_ID} | grep EBS | awk '{print $4}'`
aws ec2 delete-snapshot --snapshot-id ${SNAPSHOT_ID}
fi
fi
done