Missing Flag For nix::unistd::fchownat

[gatoWololo]

Hello!

Currently fchownat<P: ?Sized + NixPath>(dirfd: Option<RawFd>, path: &P, owner: Option<Uid>, group: Option<Gid>, flag: FchownatFlags) -> Result<()> takes an enum as it's flag argument nix::unistd::FchownatFlags. Where the variants are either FollowSymlink or NoFollowSymlink. According to man 2 fchownat since Linux 2.6.39 fchownat() may also takes AT_EMPTY_PATH as part of the flags bitmask.

This is currently not possible with the current implementation provided by Nix, the enum will probably have to be changed to a bitflag.

[asomers]

This sounds like an easy thing to fix. Would you like to write a PR to add the new flag?

[gatoWololo]

Sure! I can do that.

[otavio]

I was looking at the flags and the AT_EMPTY_PATH is Linux specific. Couldn't same thing to be done using fchown()?

[dubiousjim]

Bump. Would be great to get the functionality of fchown exposed, either as a standalone, or via the AT_EMPTY_PATH flag for fchownat. If the latter is Linux-specific, then the former seems preferable.

[asomers]

Yes, I think fchown would be a good addition. And an easy one. Would you care to submit a PR< @dubiousjim ?