setbuf(3) on macOS
The text 5a9d4426465c, as macOS 26.5, macOS 26.4, macOS 26.3, macOS 26.2, macOS 26.1, macOS 26.0, macOS 15.6, macOS 15.5, macOS 15.4, macOS 15.3, macOS 15.2, macOS 15.1, macOS 15.0 shipped it. The page shows this text now.
stream buffering operations