@node fstatat
@subsection @code{fstatat}
@findex fstatat

POSIX specification:@* @url{https://pubs.opengroup.org/onlinepubs/9799919799/functions/fstatat.html}

Gnulib module: fstatat
@mindex fstatat

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, Cygwin 1.5.x, mingw, MSVC 14.
But when the function is missing, its Gnulib substitute
is not safe to be used in libraries and is not
thread-safe.
@item
On platforms with @code{AT_EMPTY_PATH},
this function does not work when @code{AT_EMPTY_PATH}
is used with a null pointer file name:
glibc 2.40, Linux kernel 6.10, Cygwin 3.6, FreeBSD 15.1.
@item
On platforms where @code{off_t} is a 32-bit type, @code{fstatat} may
not correctly report the size of files or block devices larger than 2
GB@.  @xref{Large File Support}.
@item
On some platforms, @code{fstatat(fd,"file/",buf,flag)} succeeds instead of
failing with @code{ENOTDIR}.
Solaris 9.
@item
For symlinks, when the argument ends in a slash, some platforms don't
dereference the argument:
Solaris 9.
@item
On macOS 12.6, when this function yields a timestamp with a
nonpositive @code{tv_sec} value, @code{tv_nsec} might be in the range
@minus{}999999999..@minus{}1, representing a negative nanoseconds
offset from @code{tv_sec}.  Solaris 11.4 is similar, except that
@code{tv_sec} might also be @minus{}1000000000.
@end itemize

Portability problems not fixed by Gnulib:
@itemize
@item
This function does not fail when the second argument is an empty string
on some platforms, even when @code{AT_EMPTY_PATH} is not used:
glibc 2.7, Linux kernel 2.6.38.
@item
This function sets @code{st_ino} only to the low-order 32 bits of
the inode number of a socket or pipe, which thus can disagree
with the @code{st_ino} obtained by @code{fstat}:
macOS 14.
@item
@xref{sys/stat.h}, for general portability problems with @code{struct stat}.
@end itemize
