SHMOP (SYSV) - really shmat(2)

[Henry Spencer]

> The interprocess communication primitives included in System V (message
> queues, semaphores, and shared memory) are all very messed up.  They were
> clearly not thought out too well in either their design or implementation.

It's no particular secret that the SysV IPC swill was devised by taking the
union of several different sets of IPC mechanisms devised by different groups
within the Bell System.  This is why there's virtually no software in the
distributed Unixes that employs them:  they were invented for Bell internal
applications work, too specialized to be distributed widely.  Since each
group invented its own mechanism, software using them was very specific
to individual groups and didn't transport well enough to gain general
acceptance.  Remember that System V started out as the attempt to pull all
of the Bell-internal Unix variants together.  Naturally, each of those groups
leaned heavily on the System V people to include *their* favorite IPC scheme,
unchanged, so they wouldn't have to fix all their software.  Given that
the System V group was short on both the technical creativity to do it right
and the political clout to make the result stick, it was inevitable that they
would implement the union of the schemes rather than the intersection.

> With any luck, they'll go away soon and be replaced by something that works.

Don't get your hopes too high, given that they got into the SysV Interface
Definition (despite attempts to keep them out).
-- 
				Henry Spencer @ U of Toronto Zoology
				{allegra,ihnp4,linus,decvax}!utzoo!henry