The Single UNIX® Specification, Version 3 and UNIX 03
A Technical White Paper from the Open Group.
Version 1.01 Last update April 2004.
- Developed through the The Open Group consensus process the Single UNIX Specification Version 3
and the UNIX 03 Product Standards enhance the latest generation of UNIX systems, and reinforce the UNIX trademark as the industry
recognized mark for the leading open operating environment. The specification brings all the benefits of a single standard
operating system, namely application and information portability, scalability, flexibility and freedom of choice for customers.
Continuing its commitment to Open Systems and open availability to its specifications, The Open Group is pleased to announce
availability of the Single UNIX Specification, Version 3 on the World Wide Web at URL http://www.UNIX.org/version3/
1.1 Introduction - The Common Base Specifications
Version 3 of the Single UNIX Specification is built on the common foundation of the Austin Group
specifications (see figure below) , which are simultaneously an IEEE Standard, an Open Group Technical Standard and an ISO/IEC
International Standard. This Base document set is the common update to IEEE Std 1003.1,1996 Edition, IEEE Std 1003.2, 1992 Edition,
their ISO/IEC counterparts and the previous version of the Single UNIX Specification. The common base specifications are widely supported by the
industry, and also referenced by other specifications efforts such as
the ELC and LSB specifications.
The complete Single UNIX Specification adds X/Open Curses Issue 4 Version 2 to the Base document set
Benefits for Application Developers
- Guaranteed consistency of services and behavior amongst UNIX® operating system
- Improved portability
- Backward compatibility.
- Faster development through the increased number of standard interfaces.
- More innovation is possible, due to the reduced time spent porting applications
Benefits for Users
- An evolutionary approach that protects investment in existing systems, data and
- The availability of UNIX systems from multiple suppliers gives users freedom of choice rather than
being locked in to a single supplier.
1.3 Changes to the Single UNIX Specification
The Single UNIX Specification Version 3 incorporates the following changes:
- Extensive changes have been made to the Base Specification document set so it can simultaneously be
a standard in all three sponsoring organizations. This includes reorganization of options handling and introduction of rationale
sections in manual pages and the rationale volume.
- The following amendments to IEEE Std 1003.1-1990 (POSIX.1) are now
- IEEE P1003.1a draft standard (Additional System Services)
- IEEE Std 1003.1d-1999 (Additional Realtime Extensions)
- IEEE Std 1003.1g-2000 (Protocol-Independent Interfaces (PII))
- IEEE Std 1003.1j-2000 (Advanced Realtime Extensions)
- IEEE Std 1003.1q-2000 (Tracing)
The additions due to IEEE P1003.1a draft standard and IEEE Std 1003.1g-2000 have been
added to the mandatory requirements for the Single UNIX Specification, Version 3. The additions from
IEEE Std 1003.1d-1999, IEEE Std 1003.1j-2000, and IEEE Std 1003.1q-2000 have in general been added as
options. The reader-writer locks from IEEE Std 1003.1j-2000 duplicate the reader-writer locks already contained in the
Single UNIX Specification, Version 2 and are still mandatory.
- Sockets functionality from the Networking Services specification, Issue 5.2 (XNS5.2) has been
The 5.2 issue of the Networking Services specification superseded the version included in the Single
UNIX Specification, Version 2. The main change was the addition of IPv6 functionality.
- Alignment with ISO/IEC 9899:1999, Programming Languages - C (ISO C)
This is the latest version of the C programming language standard and is a change from the Single
UNIX Specification, Version 2.
- The 1003.2b draft standard has been incorporated adding symbolic links to the Shell and
- IEEE Std 1003.2d has been incorporated adding an optional batch service environment.
1.4 Interface Counts
As a result of the addition of new materials into the specification the interface count has risen.
The Single UNIX Specification Version 3 now has over 1700 programming interfaces, and compares with other specifications as shown
in the diagram below:
2.1 What is UNIX 03 ?
UNIX 03 is the mark for systems that a vendor guarantees as conforming to Version 3 of the Single
UNIX 03 is
If a product is registered as conformant to UNIX 03 the vendor warrants and represents that it:
- A brand that can be applied to systems (subject to license terms) that conform to the Single UNIX
Specification Version 3.
- A significant enhancement over XPG4 UNIX (UNIX 95) and UNIX 98.
- Complies with the specifications
- Will continue to comply with the specifications
- If a non-compliance is found it will be fixed in a prescribed timescale.
UNIX 03 is organized as a series of product standards addressing different market needs. The first
two of these are as follows (note that others may follow subsequently)
The following diagram shows the internet services included in the UNIX 03 Server product
- UNIX 03
- The base product standard.
UNIX 03 is made up of four constituent product standards drawn from the specifications, as shown in the diagram below:
- UNIX 03 Server
- Captures existing de-facto practice for internet/intranet services. The additional functionality
over the base UNIX 03 functionality includes:
- The Internet Protocol Suite
- Java Support
- Internet capabilities to support network clients
3.1 More Information
More information on the Single UNIX Specification, Version 3 can be obtained from the following
- The Open Group Source Book "The Single UNIX Specification, The Authorized Guide to Version 3", 480
pages, ISBN 1-85912-27709. This book provides complete information on what's new in Version 3 , and a CD-ROM containing the
complete 4000 page specification in both HTML and PDF formats (including PDF reader software). For more information see URL http://www.unix.org/version3/theguide.html.
- More information on the Single UNIX Specification , including the online version of the
specification can be obtained at The Open Group's official UNIX system world wide web site, see the URL
Copyright The Open Group, © 2004
UNIX is a registered trademark of The Open Group