dirfd() did not appear in 4.2BSD.  History added in CSRG got it wrong.

https://www.tuhs.org/cgi-bin/utree.pl?file=4.3BSD/usr/src/sys/h/dir.h
https://www.tuhs.org/cgi-bin/utree.pl?file=4.3BSD-Tahoe/usr/src/sys/h/dir.h

Index: lib/libc/gen/opendir.3
===================================================================
RCS file: /cvs/src/lib/libc/gen/opendir.3,v
diff -u -p -r1.3 opendir.3
--- lib/libc/gen/opendir.3	23 Mar 2024 16:30:01 -0000	1.3
+++ lib/libc/gen/opendir.3	19 Dec 2025 12:16:13 -0000
@@ -297,11 +297,14 @@ The
 .Fn telldir ,
 .Fn seekdir ,
 .Fn rewinddir ,
-.Fn closedir ,
 and
-.Fn dirfd
+.Fn closedir
 functions appeared in
 .Bx 4.2 .
+The
+.Fn dirfd
+function appeared in
+.Bx 4.3 Tahoe .
 The
 .Fn fdopendir
 function appeared in