fchown

fn fchown(fd: c.fd_t, owner: ?File.Uid, group: ?File.Gid) File.SetOwnerError!void {
    const uid = owner orelse std.math.maxInt(c.uid_t);
    const gid = group orelse std.math.maxInt(c.gid_t);
    while (true) switch (c.errno(c.fchown(fd, uid, gid))) {
        .SUCCESS => return,
        .INTR => {},
        .BADF => |err| return errnoBug(err), // likely fd refers to directory opened without `Dir.OpenOptions.iterate`
        .FAULT => |err| return errnoBug(err),
        .INVAL => |err| return errnoBug(err),
        .ACCES => return error.AccessDenied,
        .IO => return error.InputOutput,
        .LOOP => return error.SymLinkLoop,
        .NOENT => return error.FileNotFound,
        .NOMEM => return error.SystemResources,
        .NOTDIR => return error.FileNotFound,
        .PERM => return error.PermissionDenied,
        .ROFS => return error.ReadOnlyFileSystem,
        else => |err| return unexpectedErrno(err),
    };
}