ISO/IEC/IEEE FDIS 9945
(Main)Information technology — Portable Operating System Interface (POSIX®) Base Specifications, Issue 8
Information technology — Portable Operating System Interface (POSIX®) Base Specifications, Issue 8
ISO/IEC/IEEE 9945:2009 defines a standard operating system interface and environment, including a command interpreter (or "shell"), and common utility programs to support applications portability at the source code level. ISO/IEC/IEEE 9945:2009 is intended to be used by both application developers and system implementers and comprises four major components (each in an associated volume). General terms, concepts, and interfaces common to all volumes of this standard, including utility conventions and C-language header definitions, are included in the Base Definitions volume. Definitions for system service functions and subroutines, language-specific system services for the C programming language, function issues, including portability, error handling, and error recovery, are included in the System Interfaces volume. Definitions for a standard source code-level interface to command interpretation services (a "shell") and common utility programs for application programs are included in the Shell and Utilities volume. Extended rationale that did not fit well into the rest of the document structure, which contains historical information concerning the contents of ISO/IEC/IEEE 9945:2009 and why features were included or discarded by the ISO/IEC/IEEE 9945:2009 developers, is included in the Rationale (Informative) volume. The following areas are outside the scope of ISO/IEC/IEEE 9945:2009: graphics interfaces; database management system interfaces; record I/O considerations; object or binary code portability; system configuration and resource availability. ISO/IEC/IEEE 9945:2009 describes the external characteristics and facilities that are of importance to application developers, rather than the internal construction techniques employed to achieve these capabilities. Special emphasis is placed on those functions and facilities that are needed in a wide variety of commercial applications.
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FINAL DRAFT
International
Standard
ISO/IEC/IEEE
FDIS
ISO/IEC JTC 1/SC 22
Information technology — Portable
Secretariat: ANSI
Operating System Interface
Voting begins on:
(POSIX®) Base Specifications, Issue
2025-09-18
Voting terminates on:
2026-02-05
This document is circulated as received from the committee secretariat.
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
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MADE IN NATIONAL REGULATIONS.
Reference number
FINAL DRAFT
International
Standard
ISO/IEC/IEEE
FDIS
ISO/IEC JTC 1/SC 22
Information technology — Portable
Secretariat: ANSI
Operating System Interface
Voting begins on:
(POSIX®) Base Specifications, Issue 8
Voting terminates on:
This document is circulated as received from the committee secretariat.
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPORTING D OCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
© IEEE 2025
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO
FAST TRACK PROCEDURE
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
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Published in Switzerland Reference number
© IEEE 2024
© IEEE 2025 – All rights reserved
ii
ISO/IEC/IEEE 9945:2025(en)
Foreword
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical
Commission) form the specialized system for worldwide standardization. National bodies that are members
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In the IEC, see www.iec.ch/understanding-standards.
ISO/IEC/IEEE 9945 was prepared by the Microprocessor Committee of the IEEE Computer Society (as IEEE
Std 1003.1-2024) and The Open Group (as The Open Group Technical Standard Base Specifications, Issue 8)
and drafted in accordance with its editorial rules. It was adopted, under the “fast-track procedure” defined in
the Partner Standards Development Organization cooperation agreement between ISO and IEEE, by Joint
Technical Committee ISO/IEC JTC 1, Information technology, Subcommittee SC 22, Programming languages,
their environments and system software interfaces.
This second edition cancels and replaces the first edition (ISO/IEC/IEEE 9945:2009), which has been
technically revised. It also incorporates the Technical Corrigenda ISO/IEC/IEEE 9945:2009/Cor. 1:2013 and
ISO/IEC/IEEE 9945:2009/Cor. 2:2017.
The main changes are as follows:
— Change history is described in the Rationale (Informative) volume of POSIX.1-2024 and in the CHANGE
HISTORY section of reference pages.
© IEEE 2024 – All rights reserved
iii
ISO/IEC/IEEE 9945:2025(en)
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html and www.iec.ch/national-
committees.
© IEEE 2024 – All rights reserved
iv
IEEE Std 1003.1™-2024
(Revision of IEEE Std 1003.1-2017)
The Open Group Standard, Base Specifications, Issue 8
IEEE Standard for Information
Technology—Portable Operating
System Interface (POSIX™)
Base Specifications, Issue 8
Developed by the
Microprocessor Committee
of the
IEEE Computer Society
and
The Open Group
Approved 20 May 2024
IEEE SA Standards Board
ISO/IEC/IEEE 9945:2025(en)
TM
IEEE Std 1003.1 -2024 (Revision of IEEE Std 1003.1-2017)
IEEE Standard for Information Technology—Portable Operating System Interface (POSIX®)
The Open Group Standard, Base Specifications, Issue 8
Abstract: POSIX.1-2024 is simultaneously IEEE Std 1003.1™-2024 and The Open Group
Standard Base Specifications, Issue 8.
POSIX.1-2024 defines a standard operating system interface and environment, including a
command interpreter (or “shell”), and common utility programs to support applications portability at
the source code level. POSIX.1-2024 is intended to be used by both application developers and
system implementors and comprises four major components (each in an associated volume):
x General terms, concepts, and interfaces common to all volumes of this standard, including
utility conventions and C-language header definitions, are included in the Base Definitions
volume.
x Definitions for system service functions and subroutines, language-specific system
services for the C programming language, function issues, including portability, error
handling, and error recovery, are included in the System Interfaces volume.
x Definitions for a standard source code-level interface to command interpretation services
(a “shell”) and common utility programs for application programs are included in the Shell
and Utilities volume.
x Extended rationale that did not fit well into the rest of the document structure, which
contains historical information concerning the contents of POSIX.1-2024 and why features
were included or discarded by the standard developers, is included in the Rationale
(Informative) volume.
x
The Institute of Electrical and Electronics Engineers, Inc.
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The Open Group
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All rights reserved.
Published 14 June 2024 by IEEE in the United States of America.
PDF: ISBN 979-8-8557-0793-9 STD26978
Print: ISBN 979-8-8557-0794-6 STDPD26978
Published 14 June 2024 by The Open Group in the United Kingdom
Doc. Number: C243
ISBN: 1-957866-40-6
IEEE is a registered trademark in the U.S. Patent & Trademark Office and POSIX is a trademark owned by The Institute of Electrical and
Electronics Engineers, Incorporated.
This release of this standard is dedicated to the memory of Jörg Schilling and Donn Terry.
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ii Copyright © 2024 IEEE and The Open Group. All rights reserved.
© IEEE 2024 – All rights reserved
ISO/IEC/IEEE 9945:2025(en)
TM
IEEE Std 1003.1 -2024 (Revision of IEEE Std 1003.1-2017)
IEEE Standard for Information Technology—Portable Operating System Interface (POSIX®)
The Open Group Standard, Base Specifications, Issue 8
The following areas are outside the scope of POSIX.1-2024:
x Graphics interfaces
x Database management system interfaces
x Record I/O considerations
x Object or binary code portability
x System configuration and resource availability
POSIX.1-2024 describes the external characteristics and facilities that are of importance to
application developers, rather than the internal construction techniques employed to achieve these
capabilities. Special emphasis is placed on those functions and facilities that are needed in a wide
variety of commercial applications.
Keywords: application program interface (API), argument, asynchronous, basic regular expression
(BRE), built-in utility, byte, child, command language interpreter, CPU, extended regular expression
(ERE), FIFO, file access control mechanism, IEEE 1003.1™, input/output (I/O), job control,
network, parent, portable operating system interface (POSIX™), shell, stream, string, synchronous,
system, thread, X/Open System Interface (XSI)
The Open Group
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technology standards and open standards by fostering a culture of collaboration, inclusivity, and mutual
respect among our diverse membership of more than 900 organizations. Our membership includes customers,
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The mission of The Open Group is to drive the creation of Boundaryless Information Flow™ achieved by:
x Working with customers to capture, understand, and address current and emerging requirements,
establish policies, and share best practices
x Working with suppliers, consortia, and standards bodies to develop consensus and facilitate
interoperability, to evolve and integrate specifications and open source technologies
x Offering a comprehensive set of services to enhance the operational efficiency of consortia
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Further information on The Open Group is available at https://www.opengroup.org.
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development of Standards and Guides, but which also includes white papers, technical studies, certification
and testing documentation, and business titles. Full details and a catalog are available at
https://www.opengroup.org/library.
© IEEE 2024 – All rights reserved
ISO/IEC/IEEE 9945:2025(en)
TM
IEEE Std 1003.1 -2024 (Revision of IEEE Std 1003.1-2017)
IEEE Standard for Information Technology—Portable Operating System Interface (POSIX®)
The Open Group Standard, Base Specifications, Issue 8
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