[wfunction]

> Cutler pretended to not like the "everything is a file" approach, but NT does basically the same thing with "everything is a handle". And soon enough, you hit exactly the same conceptual limitations (except not in the same places) that not everything is actually the same, so that cute abstraction leaks soon enough (well, it does in any OS).

Explain? Pretty much the only thing you can do with a handle is to release it. That's very different from a file, which you can read, write, delete, modify, add metadata to, etc... handles aren't even an abstraction over anything, they're just a resource management mechanism.

[xorblurb]

You are right, but those points are details. FD under modern Unixes (esp. Linux, but probably others) serves exactly the same purpose (resource management). The FD where read/write can't be used just don't define those (same principle for other syscalls) -- similarly if you try to NtReadFile on an incompatible Handle it will also give you an error back. Both are in a single numbering space per process. NT largely makes use of NtReadFile / NtWriteFile to communicate with drivers, even in quite core Windows components (Winsock and AFD). And NT Handles do serve at least an abstraction (I know of): they can be signaled, and waited for with WaitFor*Objects.

So the naming distinction is quite arbitrary.

[wfunction]

> You are right, but those points are details.

Uh, no, they are very crucial details. For example, it means the difference between letting root delete /dev/null like any other "file" on Linux, versus an admin not being able to delete \Device\Null on Windows because it isn't a "file". The nonsense Linux lets you do because it treats everything like a "file" is the problem here. It's not a naming issue.

[strcat]

Linux has plenty of file descriptor types that do not correspond to a path, along with virtual file systems where files cannot be deleted...

Your example of device files is hardly universal, and the way it works is useful.

[wfunction]

And to give you another example, look at how many people bricked their computers because Linux decided EFI variables were files. You can blame the vendors all you want, but the reality is this would not have happened (and, mind you, it would have been INTUITIVE to every damn user) if the OS was sane and just let people use efibootmgr instead of treating every bit and its mother as files. Just because you have a gun doesn't mean you HAVE to try shooting youself, you know? That holds even if the manufacturer was supposed to have put a safety lock on the trigger, by the way. Sometimes some things just don't make sense, if that makes sense.

[jamespo]

How many people really did this compared to eg windows users attacked by cryptolocker?

[wfunction]

"The way it works is useful?"! When was the last time you found it useful to delete something like /dev/null via command line? And how many poor people do you think have screwed up their systems and had to reboot because they deleted not-really-files by accident? Do you think the two numbers are even comparable if the first one isn't outright zero?

It literally doesn't make any sense whatsoever for many of these devices to behave like physical files, e.g. be deletable or whatnot. Yes there is an exception to every nonsense like this, so yes, some devices do make sense as files, but you completely miss the point when you ignore the widespread nonsense and justify it with the exceptions.

[wahern]

Your complaint is with the semantics of the particular file. There's no reason why files in /dev need be deletable using unlink. That's an historical artifact, and one that's being rectified.

"Everything is a file" is about reducing most operations to 4 very abstract operations--open, read, write, and close. The latter three take handles, and it's only the former that takes a path. But you're conflating the details of the underlying filesystem implementation with the relevant abstraction--being a file implies that it's part of an easily addressable, hierarchical namespace. Being a file doesn't imply it needs to be deletable. unlink/remove is not part of the core abstraction. But they are hints that the abstraction is a little more leaky than people let on. Instantiating and destroying the addressable character of a file poses difficult questions regarding what the proper semantics should be, though historically they're deletable simply because using major/minor device nodes sitting atop the regular persistent storage filesystem was the simplest and most obvious implementation at the time.

[xorblurb]

Hm I was more thinking about open FD, not just special file entries on the FS. Well, I agree with you: it's a little weird and in some cases dangerous to have the char/block devices in the FS, and it has already been worked-around multiple times in different ways, and even in some cases simultaneously with multiple different work-around. NT is better on that point. But not once the "files" are open and you've got FD.