MacOS bash dd command with progress

dd-progress.sh

function isodump {

    FILE=$1
    DISK=$2

    if [ -z "$FILE" ] || [ -z "$DISK" ] ; then
        echo "Usage: isodump <ISO File> <DEVICE>"
        return 128
    fi

    if [ ! -f "$FILE" ] ; then
        echo "File: '$FILE' not found!"
        return 1
    fi

    if [ ! -e "/dev/r$DISK" ] ; then
        echo "Device '$DISK' not found!"
        return 2
    fi

    echo "You have to authenticate as root to proceed"
    sudo echo "Thx."

    FILSIZE=`stat -f "%z" "$FILE"`
    FILSIZE=$(( FILSIZE/1000/1000 ))
    echo "Transfering: ${FILSIZE}MB ..."

    LOG=`mktemp ${TMPDIR:-/tmp/}isodump.XXXXXX`
    # Create Subshell to suppress output of background job, also fetch job id in new pipe
    (sudo dd if="$FILE" of=/dev/r$DISK bs=1m 2> "$LOG" & echo $! >3 )
    bgid=`cat <3`

    while ps -p $bgid > /dev/null ; do
        sleep 1
        sudo kill -INFO $bgid 2>&1 >/dev/null || break
        sleep 1

        LOGLINE=`tail -n 1 "$LOG"`
        if [ ! -z "$LOGLINE" ] ; then
            BYTES=`echo $LOGLINE | awk '{print $2}'`
            if [ "bytes" == "$BYTES" ] ; then

                WRITTEN=`echo $LOGLINE | awk '{print $1}'`
                WRITTEN=$(( WRITTEN/1000/1000 ))

                SPEED=`echo $LOGLINE | awk '{print $7}'`
                SPEED=${SPEED:1}
                SPEED=$(( SPEED/1000/1000 ))

                TIME=`echo $LOGLINE | awk '{print $5}'`

                echo "${WRITTEN}MB / ${FILSIZE}MB (${SPEED} MB/s - running for ${TIME%.*}s)"
            fi
        fi

        sleep 3
    done

    rm "$LOG"
}
export -f isodump