Interprocess communication on multi-user machine

[Lawrence D'Oliveiro]

In article <e8323i$r79$1 at gemini.csx.cam.ac.uk>,
 nmm1 at cus.cam.ac.uk (Nick Maclaren) wrote:

>In article <ldo-AFFA8C.22542230062006 at lust.ihug.co.nz>,
>Lawrence D'Oliveiro <ldo at geek-central.gen.new_zealand> writes:
>|> >
>|> >Sockets are often accessed via special files, but are not files.
>|> 
>|> They are files. They are not _regular_ files.
>
>Yes, I know about UNIX-domain sockets, but even when they give the
>appearance of being files, 90% of the time that is the API only,
>and the underlying facility is very different.

Irrelevant. The userland API requires accessing a file, which is subject 
to standard *nix file ownerships and protections.

>Dammit, processes
>are not files just because they happen to have a /proc entry under
>many systems!

They are files. They have all the semantics of files. Under Linux they 
are in fact directories, but those are still files.

They are not files with blocks allocated on some physical disk 
partition, but that doesn't make them any the less files.

>|> I wasn't talking about FIFOs. Even if I was, they _are_ still subject to 
>|> regular file permissions (on Linux, at least).
>
>They aren't on most Unices - Linux is not UNIX, you know :-)

I'm not aware of any *nix system worthy of the name where they are not. 
The "everything-is-a-file" concept is deeply ingrained into the whole 
*nix philosophy.

>I shall not respond further on this.

One can hope...