How to verify SHA checksum for FreeBSD ISO file
% shasum -a 256 --ignore-missing -c CHECKSUM.SHA256-FreeBSD-13.0-RELEASE-amd64 -a : Algorithm to use. For example, 1 (default), 224, 256, 384, 512, 512224, 512256 -c : Read SHA sums from the FILEs and check them --ignore-missing : Do not fail or report status for missing files.