#!/bin/sh -e
# Assumes the existence of
${DIR_BKUP_ROOT}/{Sunday,Monday,Tuesday,Wednesday,Thursday,Friday,Saturday}

DIR_DATA="/etc"
DIR_BKUP_ROOT="/backups"

RM="/bin/rm"
CP="/bin/cp"
RSYNC="/usr/bin/rsync"
DATE="/bin/date"

[ -x $RM -a -x $CP -a -x $RSYNC -a -x $DATE ] || exit 1

TODAY=`$DATE +%A`

case "$TODAY" in 
        'Monday')
                LASTNIGHT="Sunday"
                PREVBACK="Saturday"
        ;;
        'Tuesday')
                LASTNIGHT="Monday"
                PREVBACK="Sunday"
        ;;
        'Wednesday')
                LASTNIGHT="Tuesday"
                PREVBACK="Monday"
        ;;
        'Thursday')
                LASTNIGHT="Wednesday"
                PREVBACK="Tuesday"
        ;;
        'Friday')
                LASTNIGHT="Thursday"
                PREVBACK="Wednesday"
        ;;
        'Saturday')
                LASTNIGHT="Friday"
                PREVBACK="Thursday"
        ;;
        'Sunday')
                LASTNIGHT="Saturday"
                PREVBACK="Friday"
        ;;
        *)
                echo "ERROR: Invalid day!"
                exit 2
        ;;
esac

$RM -rf ${DIR_BKUP_ROOT}/$LASTNIGHT
$CP -al ${DIR_BKUP_ROOT}/$PREVBACK ${DIR_BKUP_ROOT}/$LASTNIGHT
$RSYNC -a --delete ${DIR_DATA}/ ${DIR_BKUP_ROOT}/${LASTNIGHT}/