open (GNU Gnulib)

Gnulib module: open, fchdir

Portability problems fixed by the Gnulib module open:

Some platforms do not support O_CLOEXEC: Mac OS X 10.6, FreeBSD 8.4, NetBSD 5.1, OpenBSD 4.9, Minix 3.1.8, AIX 7.1, HP-UX 11, Solaris 10, Cygwin 1.7.x, mingw, MSVC 14.
Some platforms do not support O_DIRECTORY: glibc 2.0, Mac OS X 10.4, FreeBSD 7.4, NetBSD 4.0.1, OpenBSD 4.9, HP-UX 11, Solaris 10, Cygwin 1.5.x, mingw, MSVC 14.
On platforms where off_t is a 32-bit type, open may not work correctly with files 2 GiB and larger. See Large File Support.
This function does not fail when the file name argument ends in a slash and (without the slash) names a nonexistent file or a file that is not a directory, on some platforms: macOS 14, FreeBSD 7.2, AIX 7.1, HP-UX 11.00, Solaris 9.
This function does not support the O_NONBLOCK flag when it is defined by the gnulib module nonblocking on some platforms: mingw, MSVC 14.
On Windows platforms (excluding Cygwin), this function does usually not recognize the /dev/null filename.

Portability problems fixed by the Gnulib module fchdir:

On Windows platforms (excluding Cygwin), this function fails to open a read-only descriptor for directories.

Portability problems not fixed by Gnulib:

The Gnulib replacement for O_CLOEXEC is not atomic, and so is not safe in the presence of multiple threads or signal handlers.
The Gnulib replacement for O_SEARCH may require read access instead of search/execute access.
On some platforms, O_SEARCH may reject directories where you have search access even though O_SEARCH is not replaced: macOS 12.6.
When the file does not exist, POSIX says the behavior of O_CREAT | O_DIRECTORY is unspecified. Most platforms fail with EINVAL in this case. However, in Linux kernels 6.3 and earlier, this function creates a regular file and then either returns successfully (Linux kernel 5.6 and earlier) or fails with ENOTDIR (Linux kernels 5.7–6.3).
open ("symlink", O_CREAT ...) fails when the argument points to a nonexistent file in an existing directory on some platforms: Haiku.
open ("symlink", O_NOFOLLOW ...) fails with errno set to EMLINK instead of the POSIX-required ELOOP on some platforms: FreeBSD 14.2.
open ("symlink", O_NOFOLLOW ...) fails with errno set to EFTYPE instead of the POSIX-required ELOOP on some platforms: NetBSD 10.0.
On Windows, this function returns a file handle in O_TEXT mode by default; this means that it translates '\n' to CR/LF by default. Use the O_BINARY flag if you need reliable binary I/O.