#!/bin/sh
set -eu

# In Megabytes
export WIPE_SIZE=10

if [ -z "$1" ]
  then
    echo "Usage: `basename $0` drive1 drive2 ..."
  exit
fi

drives="$*"

verifydrives()
  {
    for drive in $drives
      do
        if [ -e /dev/$drive ]
          then
            echo "Drive $drive verified."
          else
            echo "Drive $drive does not exist. Aborting."
            exit 1
        fi
      done
  }

seeksector()
  {
    sectors=`diskinfo $drive | awk '{print $4}'`
    sectorsize=`diskinfo $drive | awk '{print $2}'`
    mb=`echo "1024000 / 512" | bc`
    offset=`echo "$mb * $WIPE_SIZE" | bc`
    echo "$sectors - $offset" | bc
  }

cleandrives()
  {
    for drive in $drives
      do
        dd if=/dev/zero of=/dev/$drive bs=1M count=$WIPE_SIZE >/dev/null 2>&1
        dd if=/dev/zero of=/dev/$drive bs=1M seek=`seeksector $drive` >/dev/null 2>&1
    done
  }

verifydrives $drives

echo ""
echo "This will irreversibly destroy partition- and filesystem data on drive(s):"
echo "$drives"
echo ""
echo "USE WITH EXTREME CAUTION!"
read -r -p 'Do you confirm "yes/no": ' choice
  case "$choice" in
    yes) cleandrives $drives
         echo ""
         echo "Drive(s) cleaned."  ;;
     no) echo ""
         echo "Cleaning cancelled."; break ;;
      *) echo ""
         echo "Cleaning cancelled."; break ;;
  esac