Copyright © 1998 The Open Group

Product Standard
Operating System and Languages: Base
Document Number: X98XB

©January 1998, The Open Group All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior permission of the copyright owners.

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Product Standard






This is the original Base Product Standard which was introduced in 1992, at a time when the IEEE Std. 1003.2 was at Draft 11.2 and nearing ratification. It was intended as a transition Product Standard to encourage migration to the new POSIX-2 standard (ISO/IEC 9945-2:1993 (POSIX-2)1).

As far as the Commands and Utilities Product Standard is concerned, a product registered as conformant to this Product Standard can be anywhere in the transition path between the XPG3 state and the POSIX standard, but its actual state must be clearly defined in its Commands and Utilities Conformance Statement.

Apart from the Commands and Utilities Product Standard, all other aspects of this Product Standard are firmly defined, and are identical to those defined for the Base 95 Product Standard.


A single configuration of the system shall meet all of the conformance requirements defined in the following Product Standards:

Except where it would imply the use of language features that require both X/Open Common Usage C and ISO C semantics, a single source program written in X/Open Common Usage C or in ISO C shall be able to use all the services provided by the Portability Interfaces of all those Product Standards.


Refer to the Product Standards listed in Conformance Requirements.


Refer to the Product Standards listed in Conformance Requirements.


Refer to the Product Standards listed in Conformance Requirements.


Refer to the Product Standards listed in Conformance Requirements.


All the mandatory functionality defined in the XPG3 Base Product Standard is included in the Base Product Standard. There are, however, some minor differences in behavior from XPG3, particularly in the area of the commands and utilities arising primarily from the transition towards the formal standard. The X/Open XPG3-XPG4 Base Migration Guide2 describes these differences and contains advice about how to avoid problems associated with the use of application code which may have depended upon implementation-defined behavior.

It should be noted that conformance to the Commands and Utilities Product Standard required to register a product to the Base Product Standard is loosely defined. A conformant system can be anywhere in the migration path between the XPG3 Commands and Utilities Product Standard and the Commands and Utilities V2 Product Standard. The degree of migration involved in moving from an XPG3 Base system to a Base system is therefore system-dependent, but can be ascertained by consulting the Conformance Statement of the Commands and Utilities Product Standard of the latter.

Any comments relating to the material contained in this document may be submitted to The Open Group at:

The Open Group
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ISO/IEC 9945-2:1993, Information Technology - Portable Operating System Interface (POSIX) - Part 2: Shell and Utilities (identical to IEEE Std 1003.2-1992).

Guide, July 1992, XPG3-XPG4 Base Migration Guide (ISBN: 1-872630-49-9, G204).