gistfile1.txt

#!/bin/bash

## NOTE: to merge divergent backups use: 
##
##   rsync -aiuP <older>src/ <newer>dest/
##

set -e

BDIR=/path/to/plugged/usb/disk/BACKUPS
TARGETS="/paths /to /back /up"
OWNER_AND_GROUP="owner:owner"

if [ ! -d "${BDIR}" ]; then
    echo "Insert backup USB"
    exit 0
fi

# Report out old and new backup times
if [ -f "${BDIR}/info/time.txt" ]; then
    OLD_TIME=$(cat "${BDIR}/info/time.txt")
else
    echo "Failed to find file ${BDIR}/info/time.txt file, aborting."
    echo "Touch it to create an empty file there to proceed."
    exit 0
fi
NEW_TIME=$(LANG=en date +"%F:%H")

# Make the log file
# echo "" > "${BDIR}/info/rsync-$(cat ${BDIR}/info/time.txt).log"

# Make the target directory
if [ ! -d "${BDIR}/BACKUP-IN-PROGRESS" ]; then
    sudo mkdir "${BDIR}/BACKUP-IN-PROGRESS"
    sudo chown ${OWNER_AND_GROUP} "${BDIR}/BACKUP-IN-PROGRESS"
fi

cd ~/.

sudo rsync -avhPR \
    --stats \
    --log-file="${BDIR}/info/rsync-${NEW_TIME}.log" \
    --exclude-from="${BDIR}/info/exclude.txt" \
    --link-dest="${BDIR}/${OLD_TIME}" \
    ${TARGETS} \
    "${BDIR}/BACKUP-IN-PROGRESS"

sudo echo "Last backup: ${OLD_TIME}"
echo "This backup: ${NEW_TIME}"

#move 
sudo mv "${BDIR}/BACKUP-IN-PROGRESS" "${BDIR}/${NEW_TIME}"
    
#overwrite old time.txt file with new time
sudo echo ${NEW_TIME} > "${BDIR}/info/time.txt"