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>>> n = os.open('/tmp', os.O_RDONLY)
>>> l = os.listdir(n)
>>> os.listdir in os.supports_dir_fd
False

I want to mark this as wontfix.
>>> os.listdir in os.supports_fd
True
The concept we're struggling with here: is the "fd" you pass in to os.listdir a "dir_fd"? I claim that it isn't. I'm trying to enforce the concept, in both the documentation and the code, that "dir_fd" is a directory fd *accompanying a path*. With listdir, it isn't accompanied by a path, it replaces the path. So I suggest it's not a "dir_fd", it's just an "fd" which by sheer coincidence happens to reference a directory.
I proposed making os.listdir accept dir_fd, and internally use open and listdir to emulate the behavior. But someone (Antoine?) rightly pointed out, this would break the guideline that POSIX os.* functions on Unix-y OSes are atomic.
I might go so far as to say this needs a documentation fix. But I won't condone any sort of code fix (like adding os.listdir to os.supports_dir_fd).

I don't really care about the name but I'd really like some way to check whether listdir supports fds.

Like I said: use os.supports_fd.

Ah sorry, that wasn't in the mail (stupid >>>).

I'm closing this. os.listdir should not be listed in supports_dir_fd, because it has no dir_fd parameter.
For reference, we discussed all this previously in issue #15176.

> I proposed making os.listdir accept dir_fd, and internally use open and listdir to emulate the behavior.
Hmm, I understood the issue as the request for adding dir_fd argument to
os.listdir. openat+fdopendir+readdir+closedir+close or, in Python,
def listdir2(path, dir_fd=None):
 fd = os.open(path, dir_fd)
 try:
 return os.listdir(fd)
 finally:
 os.close(fd)
> But someone (Antoine?) rightly pointed out, this would break the guideline that POSIX os.* functions on Unix-y OSes are atomic.
os.listdir is not atomic. opendir+readdir+closedir+close or fdup
+fdopendir+readdir+closedir+close.

Storchaka: please take it up with Antoine, he's the defender of the realm for POSIX-functions-are-atomic iirc. I'd be happy with dir_fd for os.listdir, though it may be too late for 3.3 anyway.

Just in my defense: Larry suggested in msg164245 to me to check for listdir in supports_dir_fd so I just assumed it's broken as it didn't work. I'm totally fine with the current behavior, the discussion about dir_fd support in listdir isn't what I intended with this ticket.

> Storchaka: please take it up with Antoine, he's the defender of the realm for POSIX-functions-are-atomic iirc. I'd be happy with dir_fd for os.listdir, though it may be too late for 3.3 anyway.
I know that this is possible (and relatively easy), but I don't think
it's useful. If you use at-functions, then after listdir should be
at-function, and for this purpose you need to get directory's fd in any
case. I don't see useful use cases for listdir(name, dir_fd). So I'm not
going to open a new issue and I'm happy with closing this one.

WFM. That is, unless people want to bring up additional only-tangentially-related topics to annoy Hynek ;-)
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