#!/bin/sh

# checksum the first N bytes of a device
# compare against expected result and return pass / fail
# usage: checksum-device filepath size_of_filepath expected_sum

set -eu

infile=$1
infile_size=$2
expected=$3

actual=$(dd "if=$infile" iflag=count_bytes "count=$infile_size" \
         | sha256sum | cut -d' ' -f1)
[ "$actual" = "$expected" ]
