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)

Direct command to do it all and create two files in your current directory:

wget -O - https://gist.github.com/theKAKAN/69bfb34084802c4052880ca64413b3fd/raw/3a7f590533fbf62d26784f5f7204db5cb5e193ab/backup-packages-name.sh -nv -q | sh

For DNF package manager. This should work well in Fedora and other RHEL distros with DNF installed

# Backup all DNF repos
dnf repoquery --qf '%{name}' --userinstalled \
| grep -v -- '-debuginfo$' \
| grep -v '^\(kernel-modules\|kernel\|kernel-core\|kernel-devel\)$' \
> "$(date) Packages.list"

For Flatpaks

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