Re: light weight user level semaphores

Linus Torvalds
2001-04-19T20:56:19Z

On Thu, 19 Apr 2001, Ingo Oeser wrote:

> On Thu, Apr 19, 2001 at 09:11:56AM -0700, Linus Torvalds wrote:
> > No, this is NOT what the UNIX dogmas are all about.
> >
> > When UNIX says "everything is a file", it really means that "everything is
> > a stream of bytes". Things like magic operations on file desciptors are
> > _anathema_ to UNIX. ioctl() is the worst wart of UNIX. Having magic
> > semantics of file descriptors is NOT Unix dogma at all, it is a horrible
> > corruption of the original UNIX cleanlyness.
>
> Right. And on semaphores, this stream is exactly 0 bytes long.
> This is perfectly normal and can be handled by all applications
> I'm aware of.

It's perfectly normal, but it does NOT conform to the idea "everything is
a file".

The fact that there are other ugly examples (ioctls and special files)
does not mean that adding a new one is a good idea.

When people say "everything is a file", they mean that it can be _used_ as
a file, not that it can passably return a valid error code.

Linus