sha256sum
Transfer and archivesPackage: coreutils
Computes or checks a file's SHA-256 digest. sha256sum -c compares a download with the published digest — the only proof the file received is the one announced.
What its options do in the lessons
From the same glossary the lessons render under their commands, so the two cannot disagree.
sha256sum -c- Checks the digests listed in a file instead of computing them. Answers
OKper line,FAILEDotherwise, and exits non-zero: what turns a transfer assumed to have worked into an established fact.