From chdir function ...

...
chdir FILEHANDLE
chdir DIRHANDLE
...
  On systems that support fchdir(2), you may pass a filehandle or dire
+ctory handle as the argument. On systems that don't support fchdir(2)
+, passing handles raises an exception.
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... fchdir(2) ought to be present on POSIX-conforming systems, from "fchdir(2)" manual page of FreeBSD 14 ...

...
STANDARDS
     The chdir() system call is expected to conform to IEEE Std 1003.1
+-1990 (“POSIX.1”).

HISTORY
  The chdir() system call appeared in Version 1 AT&T UNIX. The fchdir(
+) system call appeared in 4.2BSD.
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