rev(1) on OpenBSD
The text 7a10e4ccaa8d, as OpenBSD 6.0, OpenBSD 5.9, OpenBSD 5.8, OpenBSD 5.7, OpenBSD 5.6, OpenBSD 5.5, OpenBSD 5.4, OpenBSD 5.3, OpenBSD 5.2, OpenBSD 5.1, OpenBSD 5.0, OpenBSD 4.9, OpenBSD 4.8, OpenBSD 4.7 shipped it.
reverse lines of a file