@node fchmodat
@section @code{fchmodat}
@findex fchmodat

POSIX specification:@* @url{http://www.opengroup.org/onlinepubs/9699919799/functions/fchmodat.html}

Gnulib module: fchmodat

Portability problems fixed by Gnulib:
@itemize
@item
This function is missing on some platforms:
glibc 2.3.6, Mac OS X 10.5, FreeBSD 6.0, NetBSD 5.0, OpenBSD 3.8, Minix 3.1.8,
AIX 5.1, HP-UX 11, IRIX 6.5, OSF/1 5.1, Solaris 10, Cygwin 1.5.x, mingw, MSVC 14, Interix 3.5, BeOS.
But the replacement function is not safe to be used in libraries and is not multithread-safe.
@end itemize

Portability problems not fixed by Gnulib:
@itemize
@item
Some platforms do not allow changing the access bits on symbolic
links.  POSIX states that @code{fchmodat(@dots{},AT_SYMLINK_NOFOLLOW)}
may fail with @code{EOPNOTSUPP} when called on a symlink, but some
platforms, as well as the gnulib replacement, fail for any use of
AT_SYMLINK_NOFOLLOW even if the target was not a symlink:
glibc, Cygwin.
@end itemize