That’s not a builtin, so wouldn’t it be:
#include <old-man-shouting-at-clouds.h>And it's kinda old, so maybe
#define _POSIX_C_SOURCE 1
#include <old-man-shouting-at-clouds.h>
Now I am dismayed with juniors who can't even be bothered to use google (or llms) to look up stuff on their first hiccup.
#include <old-man-shouting-at-clouds>