Hi everyone. I noticed that `<unistd.h>` doesn't define `sync`, `crypt`, and some other functions. Looked into the man page `unistd.h.0p` and sees nothing about XSI in the function declarations. Looked at the website, you can see the clear XSI refrences here^[1]. Needed to define `_XOPEN_SOURCE` to make them work. This information should be avaliable to the man-page reader. But it was not included by the automatic manual generation. The XSI requirement information was in the format (raw HTML): <sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0"> ...functions that needs XSI extenion support goes here... <img src="../images/opt-end.gif" alt="[Option End]" border="0"> Note that this can include more than one function at a time. The guys at IEEE suck designing anything. - [1] https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/unistd.h.html#tag_13_77_03_06