backup_incremental.sh

#!/usr/bin/env bash

# Made by erikano for use on FreeBSD 10.1
#
# This script assumes that a previous backup exists
# with the expected file name format.
#
# You need to change some stuff if you want to use this.
#
#  * Script is using hard-coded directory names and such.
#
#  * No effort has been made to make this script portable.
#    E.g. GNU stat does not understand what we're saying here.

# Though this script will detect files with changes to ownership/permissions
# thanks to checking ctime, one might argue that it's inefficient to backup
# the whole file again for inode changes only. That is true, but so is
# the fact that backing up a whole file again for as little as
# a single byte change is almost as inefficient. This is a design decission and
# I'm sticking with it until the effect of this choice forces me
# to do something about it.

export TZ=Europe/Oslo
cd /usr/local/www/

cmp=$( find ~/backup/ -name www-erikano-net-archive\* \
         -exec stat -f "%Sm %N" -t "%Y-%m-%d %H:%M" {} \; \
       | sort -n -r \
       | head -n1 )

find net.erikano.www/ ! -path net.erikano.www/ \
  -newer "$( echo $cmp | cut -d' ' -f3- )" \
  -or -cnewer "$( echo $cmp | cut -d' ' -f3- )" \
| cmp -s /dev/null -

if [ $? -ne 0 ] ; then
  tar \
    --exclude-from ./net.erikano.www/.backup-exclude \
    --newer "$( echo $cmp | cut -d' ' -f1-2 )" \
    -cvf ~/backup/www-erikano-net-archive-incr-$( date +%Y-%m-%dT%H%M%S%z).tar \
    net.erikano.www/
fi

I should probably just -exec from find in that one place where I'm piping to xargs. Done.

Changed as per comment above. Also decided to sort in reverse order and take the first line instead of normal sort and last line. Also, sorting numerically now.

Does not detect changes in ownership/permissions. tar will notice, though, so if there are other changes, tar will also include the files on which ownership/permissions changed. Must look into the different time stamps and what I'm checking on. Fixed. (See note in comment below.)

(Contents of this comment moved inline of script.)

Created a repository for what'll replace this. https://github.com/erikano/binc