#!/usr/local/bin/bash

# incremental backup script, written by Travis Morgan Aug 17, 2005
# Note that this was written for FreeBSD 5.4 and so may not work with
# other unix versions because of the differences in how they do time formats
# released under the GPL version 2

src="/path/to/source"
dest="/path/to/destination"
curtime=`date "+%s"`
name="incremental"

# check the source dir exists
if [ ! -d "$src" ] ; then
	echo "Source directory $src does not exist. Exiting.."
	exit
fi

# check the dest dir exists
if [ ! -d "$dest" ] ; then
	echo "Creating destination directory $dest.."
	mkdir -p "$dest" || {
		echo "Could not create destination directory $dest. Exiting.."
		exit
	}
fi

# if the day is sunday delete the timestamp.done to force a full backup
if [ "`date "+%a"`" = "Sun" ] ; then
	rm -f "$dest/timestamp.done"
fi

# find out when we last made a backup
if [ -f "$dest/timestamp.done" ] ; then
	lasttime=`stat -f "%m"`
else
	lasttime=0;
	name="full"
	touch -m -t `date -j -f "%s" "$lasttime" "+%Y%m%d%H%M.%S"` "$dest/timestamp.done"
fi

# create a new timestmap file for use with find
rm -f "$dest/timestamp.new"
touch -m -t `date -j -f "%s" "$curtime" "+%Y%m%d%H%M.%S"` "$dest/timestamp.new" 

echo -e "$dest/timestamp.done\n$dest/timestamp.new" > "$dest/filelist.txt"

# find all files that have modification times between last backup and this one
cd "$src" || {
	echo "Cannot change directory to $src.. Exiting."
	exit
}
find "." -newer "$dest/timestamp.done" -and -not -newer "$dest/timestamp.new" >> "$dest/filelist.txt" 2>/dev/null 
tar -zcnvf "$dest/$name-`date -j -f "%s" "$curtime" "+%Y%m%d-%H:%m:%S"`.tgz" -T "$dest/filelist.txt"
rm "$dest/filelist.txt"

# update the old timestamp to the new time
touch -m -t `date -j -f "%s" "$curtime" "+%Y%m%d%H%M.%S"` "$dest/timestamp.done" 

now=`date "+%s"`
echo "The backup took $(($now - $curtime)) seconds to complete."