Read Magento connection settings from local.xml and backup database

backup.sh

#!/bin/sh

##
## save to "shell" dir and call every few hours from cron
##

## find root dir of Magento site, do not rely on current dir
DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
DIR=$(dirname $DIR)
LOCAL_XML=$DIR/app/etc/local.xml

## because xmllint doesn't parse CDATA tag for us
function value {
    if [[ $@ =~ ^\<!\[CDATA\[(.+)\]\]\>$ ]]
    then
        echo ${BASH_REMATCH[1]}
    else
        echo $@
    fi
}

## xmllint is part of libxml which is very widespread and has good XPath implementation
DB_HOST=$(value $(xmllint --xpath '/config/global/resources/default_setup/connection/host/text()' $LOCAL_XML))
DB_NAME=$(value $(xmllint --xpath '/config/global/resources/default_setup/connection/dbname/text()' $LOCAL_XML))
DB_USER=$(value $(xmllint --xpath '/config/global/resources/default_setup/connection/username/text()' $LOCAL_XML))
DB_PASS=$(value $(xmllint --xpath '/config/global/resources/default_setup/connection/password/text()' $LOCAL_XML))

## create simple backup dir and file
mkdir -p "$DIR/var/backups"
DATE=$(date '+%Y-%d-%m_%H-%M')
mysqldump -u "$DB_USER" "-p$DB_PASS" -h "$DB_HOST" "$DB_NAME" | gzip > "$DIR/var/backups/database_$DATE.sql.gz"

## delete backups two whole days past or older
find $DIR/var/backups/database* -mtime +1 -delete