#INIT
backup_diff_dir=''
source_dir='/home/test/source/'
backup_dir='/home/test/backup/'

cd $backup_dir

#CHECK FULL BACKUPS
backup_full_dir='none'
for i in $(ls -dX */|grep FULL_)
do 
  backup_full_dir=$i
done

if [ $backup_full_dir == 'none' ]
then
  echo 'No FULL backup found in $backup_dir'
  exit 1
fi

#DIFF
backup_date=$(date +%Y%m%d_%H%M%S)
backup_id=$(echo $backup_full_dir|cut -d'_' -f4)
backup_name='DIFF_'$backup_date'_'$backup_id
tar_file=$backup_dir${backup_name%/}'.tar.gz'

mkdir $backup_name
backup_diff_dir=$backup_dir$backup_name

rsync -av --compare-dest=$backup_dir$backup_full_dir $source_dir $backup_diff_dir

tar --remove-files -czPf $tar_file $backup_diff_dir

exit 0