Where is renameat2 on Catalina? https://www.unix.com/man-page/osx/2/renameat/
I see osx has renameat2 as shown here. But I don't find it on Catalina. Could anybody where I can find the manpage of renameat2?
EDIT: man renameat gives me something like this. But renameat2 does not exist on the manpage.
RENAME(2)                   BSD System Calls Manual                  RENAME(2)

NAME
     rename, renameat, renamex_np, renameatx_np -- change the name of a file

SYNOPSIS
     #include &lt;stdio.h&gt;

     int
     rename(const char *old, const char *new);

     int
     renameat(int fromfd, const char *from, int tofd, const char *to);

     int
     renamex_np(const char *from, const char *to, unsigned int flags);

     int
     renameatx_np(int fromfd, const char *from, int tofd, const char *to, unsigned int flags);

The path of renameat's manpage is here.
$ man -w renameat
/Library/Developer/CommandLineTools/SDKs/MacOSX10.15.sdk/usr/share/man/man2/rename.2
The man page you link to says:
renameat2() is Linux-specific.

It's never going to be in macOS.
Several other references point to that man page being Linux, not BSD 4.2. It's clearly a mistake.