On Thu, Sep 09, 2004 at 03:32:28PM -0400, Beman Dawes wrote:
Yes, is_accessable() might be useful. But the use cases I can think of are a bit theoretical. Anyone else have an opinion? I think I'd like to hear about so real-life needs (rather than theoretical or hypothetical needs) before deciding.
It makes sense. The only reasonable result for is_directory() when a parent directory in the path is not reachable, is to return false or throwing. But you can't return 'false' because it is possible that the path really is a directory OR it doesn't exist even; and the policy is to thrwo when it doesn't exist. You also can't throw because, like you said, that should be a real error; I don't think that inaccessibility for a mere query should be considered a serious error of this type. My conclusion is that throwing is the only option, but that the coder should get a fair chance of avoiding the need to catch that exception by providing the additional test is_accessable. is_accessable then should return false when it is not possible to determine the existance and/or type of the path passed to it. I understand that the original proposal also tried to solve a possible race condition. For example, code now will look like: if (is_accessable(p) && is_directory(p)) in an attempt to avoid exceptions. However, it is possible that right after the call to is_accessable - a parent directory is made in-accessable; in which case you still get an exception; that doesn't seem right I have to admit. Not that I'd care ;) Thanks -- Carlo Wood <carlo@alinoe.com>