#! /bin/bash

#
# backup cosmicvoyage files to a dir in your homedir
#
# put it into your crontab
# 0 22 * * *      $HOME/bin/backup_cosmicvoyage
#
# alexlehm@cosmic.voyage
#

SHIPS=~/ships
BACKUP=~/backup-ships

test -d $SHIPS || (echo "ships does not exit" ; exit 1)

test -d $BACKUP || mkdir $BACKUP

OLDBACKUP=$(find $BACKUP -name "ships-*.tar.gz" -print|sort|tail -1)

cd $SHIPS || exit

TS=$(date -u +%Y-%m-%dZ%H%M)

TGZ="$BACKUP/ships-$TS.tar.gz"

# if you run the script more than once within 1 minute it gets
# confused

if [ -f "$TGZ" ]
then
    echo "backup file $TGZ already exists, not overwriting"
    exit 1
fi

echo "backing up $SHIPS/* to $TGZ"

# have to use */* since it would otherwise backup the symlinks and not
# the target, maybe we could use an option in tar otherwise

tar cvfz "$TGZ" ./*/* ./*/.??*

# don't keep backup file if nothing has changed

if [ -f "$OLDBACKUP" ] && cmp -s "$OLDBACKUP" "$TGZ"
then
    echo "nothing has changed, no new backup"
    rm -f "$TGZ"
else
    echo "file is different, keeping new file"
fi

test -f "$TGZ" && echo "backup of file $TGZ was successful"