backup.sh

#!/bin/sh
#
# script to backup to a mounted sparseimage
#
# tests if the image is mounted and if not,
# tries to mount it. After backup, the image
# is detached again
#

SOURCE=~/
DEST="/Path/To/Backup_folder"
SPARSEIMAGE="/Path/To/Backup_image.sparsebundle"
EXCLUDE_FILE="/Path/To/Excludefile"
TIME=`date "+%Y-%m-%d %H:%M"`

backup () {
    if [ ! -d $DEST ]
    then
        if [ -d $SPARSEIMAGE ]
        then
            hdiutil attach $SPARSEIMAGE -quiet
            echo "Backup image attached."
            backup
        else
            echo "No backup image present. Aborting."
            exit -1
        fi
    elif [ -d $DEST ]
    then
        rsync --recursive -z -a \
        --exclude-from=$EXCLUDE_FILE --delete $SOURCE $DEST
        echo "Backup done."
        MOUNT=`hdiutil info | grep $DEST | grep disk \
        | awk '{print $1}'`
        hdiutil detach $MOUNT -quiet
        echo "Backup image detached."
        exit 0
    fi
return
}
echo $TIME
backup

launch.plist

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple Computer//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
    <dict>
        <key>KeepAlive</key>
        <false/>
        <key>Label</key>
        <string>FILELABEL</string>
        <key>ProgramArguments</key>
        <array>
            <string>/Path/To/backup.sh</string>
        </array>
        <key>StartInterval</key>
        <integer>3600</integer>
        <key>RunAtLoad</key>
        <true />
        <key>StandardErrorPath</key>
        <string>/dev/null</string>
        <key>StandardOutPath</key>
        <string>/Path/To/Logfile</string>
    </dict>
</plist>