Quickly calculate a checksum for a file and compare with input

comparechecksum.sh

#!/bin/bash
# compare calculated from file and input checksums for any hash function

if [ $# -lt 3 ] ; then
	echo 'usage -- comparechecksum hashfunction filename checksum'
	exit 1
fi

[ $($1 $2 | cut -f 1 -d " ") == $3 ] && echo "OK: All good" || echo "NOT OK: File does not match given checksum"