On Sun, 23 May 1999, Juanjo Marin wrote:
> Hi Hosam,
>
> You can find more information about Linux and POSIX.4 (POSIX 1003.1b after
> the big renumbering) in the following url:
> ftp://ftp.informatik.uni-erlangen.de/local/cip/mskuhn/misc/linux-posix.1b
>
> One thing that you have to take into account is the fact that POSIX.1b is
> structured as a set of options that a vendor can support or not. Only some
> functions are compulsory to say that a system is POSIX.1b compliant (If 'm
> not wrong these options are the queue signals and not much more).
>
to add another word of caution is that support for POSIX.1b options
does not necessarily mean that the system is good for hard real time.
especially with Linux. the options NOT supported so far are
_POSIX_TIMERS (not implemented)
_POSIX_PRIORITIZED_IO (not implemented)
_POSIX_MESSAGE_PASSING (not implemented - that's for message queues)
_POSIX_SHARED_MEMORY_OBJECTS (not implemented)
all other options (see that paper above or the book below) are
supported in teh new kernel 2.2.x with glibc-2.1. posix semaphores are
partially supported. the missing options in teh previous kernel are
real time signals I think. and that's not to say that other non posix
options are not there for message queues or shared memory (system V).
and a last note is taht the use of RTLinux forfeits tha LINUX support for
POSIX since it's all part of LInux whihc is now a low priority process.
Some POSIX.1b calls seem to be implemented as part of RTLinux in that new
beta version for 2.2.9 but taht too appears to be a work in progress.
> RTLinux, as far I know, is not a POSIX way but is a REAL way to get a RT
> system working. Another POSIXish alternative is QNX (www.qnx.com) for
> example, but it's commercial.
>
> Finally, if you're interested in the POSIX way I strongly recommend the
> following book "POSIX.4: Programming for the real world, Bill O.
> Gallmeister, O'Reilly & Associates, 1995"
>
> best regards,
>
> Juanjo
- Vladimir
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