Backup script which will backup all the files in a custom directory, will create a tar.xz archive and will delete previous backup files in case the md5sum is the same.

backup.sh

#!/bin/bash

target_dir=""
bkp_dir=""

while [[ ! $bkp_dir =~ [a-zA-Z] && ! -d "$bkp_dir" ]];
do
    echo "Please enter a valid directory to backup:"
    read -r bkp_dir
done

while [[ ! $target_dir =~ [a-zA-Z] ]];
do
    echo "Please enter a valid backup directory name:"
    read -r target_dir
done

if [ ! -d "$target_dir" ]; then
    echo "Creating the new backup directory: $target_dir"
    mkdir -p "$target_dir";
fi

now="$(date +'%Y%m%d')"

tar cfJ "$HOME"/backup/"${now}"_backup.tar.xz "$bkp_dir" &> /dev/null

# Evaluates the md5sum of the most recent backup and compares its md5sum against the other files in the same directory. If the md5sum is the same removes the duplicated file

md5sum_now=$(md5sum "$target_dir"/"${now}"_backup.tar.xz | awk '{ print $1 }')
for filename in $target_dir/*.tar.xz;
do
        if [[ "$md5sum_now" == $(md5sum "$filename" | awk '{ print $1 }') ]] && [[ "$filename" != "$target_dir"/"${now}"_backup.tar.xz ]]
        then
                rm "$filename"
        fi
done