Format a disk with pseudo-randon data using /dev/null encrypted with a random number

format-pseudo-random.sh

#!/bin/sh
# Format a disk with pseudo-randon data using /dev/null encrypted with a random number

# Dependencies
# - base64
# - openssl
# - pv

DISK="$1"
UNAME=$(uname)

if [ "$(uname)" == "FreeBSD" ]; then
  DISKSIZE=$(diskinfo -v "$DISK" | grep "mediasize in bytes" | awk '{ print $1 }')
fi

# Linux
if [ "$(uname)" == "Liunx" ]; then
  DISKSIZE=fdisk -l "$DISK"  | head -n1 | awk '{ print $5 }'
fi

# User Confirmation
echo -n "The disk $DISK ($DISKSIZE bytes) will be deleted. Please enter uppercase YES to continue: "
read user_confirmed
if [ "$user_confirmed" != "YES" ]; then
  echo "aborted. exiting"
  exit 0;
fi

openssl enc \
  -nosalt \
  -aes-256-ctr \
  -pass pass:"$(dd if=/dev/urandom bs=128 count=1 2>/dev/null | base64)" \
  < /dev/zero |
  pv --progress --eta --rate --bytes --size "$DISKSIZE" |
  dd of="$DISK" bs=2048