Backs up all the installed packages using pacman. Can be used to reinstall them later...

backup-packages-name.sh

#!/bin/bash
# A script to back up all the program names.
# Can be used to install them again later on

TSTAMP=`date +%H:%M_%d-%m-%Y`

# Get all the programs available in the repos
# And paste them in a file
pacman -Qentq > ./native-packages_${TSTAMP}.txt

# Get all foreign packages
pacman -Qmq > ./foreign-packages_${TSTAMP}.txt


# To use it, download the file and execute it
# bash ./filename.sh

# To use the backed up files, use:
# pacman -S $(cat backup-file-name)

For Flatpaks

flatpak list -a --columns=application \
| grep -v -- "Application ID$" \
> "$(date) flatpak Packages.list"