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====== POSIX and MINIX 3 ======
MINIX 3 is POSIX conformant. This document discusses what that means.

=====  What is POSIX?  =====

<code> 
"To make it possible to write programs that could run on any UNIX
system, IEEE developed a standard for UNIX, called POSIX, that most
versions of UNIX now support.  POSIX defines a minimal system call
interface that conformant UNIX systems must support.  In fact, some
other operating systems now also support the POSIX interface."
    -- Operating Systems Design and Implementation, 2nd ed., p. 11
</code>



Before the release of Minix 2.0.0, efforts were made to check
it against the then-current version of the official POSIX standard,
//International Standard ISO/IEC 9945-1//, also known as 
//ANSI/IEEE Std 1003.1, First edition, 1990-12-07//.  
The full name of the document is ''Information Technology -- Portable Operating System Interface (POSIX)
part 1: System Application Programming Interface (API) [C Language]''. 
There have been a number of revisions and extensions since 1990. As of early
2005, the latest version of the basic document is known as
''IEEE Std 1003.1, 2004 Edition, Single UNIX Specification Version 3
''.

=====  Where Can I Get a Copy of the POSIX Standard? =====


Hard copy is available from the
[[http://www.ieee.org/ |IEEE (Institute of Electrical and Electronics Engineers)]] 
in New York.  It's expensive, however.  Even paying to have a PDF document e-mailed to you is quite
expensive.  You can get information on purchasing IEEE documents
on-line at [[http://standards.ieee.org/ | http://standards.ieee.org/]].  
You might also do well to look in the engineering library of a local university.  




Possibly more useful than the IEEE document, and certainly considerably
less expensive, is the book 
[[http://www.oreilly.com/catalog/posix/index.html|POSIX Programmer's Guide]], 
by Donald Lewine, published by O'Reilly.  It's listed at about US$35 on
[[http://www.amazon.com/exec/obidos/tg/detail/-/0937175730/qid=1109451696/sr=1-6/ref=sr_1_6/103-8500237-7807003?v=glance&amp;s=books|Amazon]], 
with used copies from US$16 (prices noted Feb 2005) .




The 
[[http://www.opengroup.org/|Open Group]]
has the [[http://www.unix.org/version3/|Single Unix Specification]] 
online.  They want you to register, but you can read documents on-line
for free.  You can also buy hard copy or text on CD-ROMs, from their
site, but these are expensive, too.  


=====  Does POSIX Compliance Mean I Can Compile Any Program from Another POSIX-Compliant System on MINIX 3?  =====



Well, maybe...  in principle, yes, but many systems (Minix included)
provide extensions to the basic C library functions defined by POSIX,
so you may have to deal with these in porting a program.  Also,
standards, no matter how carefully defined, may contain elements that
can be interpreted more than one way.  Many things outside the scope of
a standards document may make porting a program difficult.  The GNU
version of the //make(1)// utility, for instance, provides
facilities that are not present in the Minix version; you might have to
either port GNU make first or devote some effort to modifying a
Makefile before you could compile on Minix a package developed on a
GNU-ish system.  Finally there may be basic assumptions about system
resources that affect how a program works.  One that often affects
Minix users is the lack of virtual memory -- programmers writing for
environments that provide virtual memory may assume that memory is
effectively unlimited.  This is very much a problem with 16-bit Minix;
for 32-bit Minix it is becoming less problematic as newer computers
come equipped with amounts of physical memory undreamed of just a few
years ago.
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