Functions for creating checksum files and easily testing them against the parent file. These go in your .bashrc file. Works on Linux.

md5-sidecar

md5sc()
{
	local target="$1"
	local checksumString=$(md5sum "$target")
	local checksum=${checksumString:0:32}
	echo "$checksum" > "$target.md5"
	echo "$checksum $target"
}

md5v() #md5 verifies a file based on it's .md5 sidecar file. return 0 == passed.
{
	local target="$1"
	local targetNameLength=${#target}
	let targetNameLength-=4
	local targetExtension=${target:targetNameLength:4}

	local controlChecksum=0 #checksum in sidecar file
	local testChecksumTarget=0 #file to create checksum from
	if [ "$targetExtension" == ".md5" ]; then
		controlChecksum=$(cat "$target")
		controlChecksum=${controlChecksum:0:32}
		testChecksumTarget=${target:0:targetNameLength}
	else
		controlChecksum=$(cat "$target.md5")
		controlChecksum=${controlChecksum:0:32}
		testChecksumTarget="$target"
	fi

	local testChecksum=0 #checksum of file we're verifying
	if [ -e "$testChecksumTarget" ] && [ "$controlChecksum" != "" ]; then
		local testChecksumString=$(md5sum "$testChecksumTarget")
		testChecksum=${testChecksumString:0:32}
		if [ "$controlChecksum" == "$testChecksum" ]; then
			echo "Control: $controlChecksum"
			echo "Test   : $testChecksum"
			echo "$testChecksumTarget passed verification!"
			return 0;
		else
			echo "Control: $controlChecksum"
			echo "Test   : $testChecksum"
			echo "$testChecksumTarget FAILED verification!"
			return 1;
		fi
	else
		echo "Sidecar or target file missing or unreadable."
	fi
}