It sounds correct, I verified `man errno` for freebsd, openbsd, linux and all mention `<errno.h>` I think it comes from macos, where `man errno` does not answer anything usefull... But where I get this answer to `man 2 intro`
**NAME** intro -- introduction to system calls and error numbers
**SYNOPSIS** #include <sys/errno.h>
**DESCRIPTION** This section provides an overview of the system calls, their error returns, and other common definitions and concepts.