ISO/IEC/IEEE FDIS 9945

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.

Technologies de l'information — Spécifications de base de l'interface pour la portabilité des systèmes (POSIX®), Issue 8

General Information

• Status: Not Published
• ICS: 35.060 - Languages used in information technology
• Technical Committee: ISO/IEC JTC 1/SC 22 - Programming languages, their environments and system software interfaces
• Drafting Committee: ISO/IEC JTC 1/SC 22 - Programming languages, their environments and system software interfaces
• Current Stage: 5020 - FDIS ballot initiated: 2 months. Proof sent to secretariat
• Start Date: 18-Sep-2025
• Completion Date: 18-Sep-2025

Relations

• Revises: ISO/IEC/IEEE 9945:2009 - Information technology - Portable Operating System Interface (POSIX®) Base Specifications, Issue 7
• Effective Date: 10-May-2025

Overview

ISO/IEC/IEEE FDIS 9945, also known as POSIX® Base Specifications, Issue 8, is an international standard that defines a portable operating system interface. Developed collaboratively by ISO, IEC, and IEEE, this specification establishes a standardized environment for operating systems that supports application portability at the source code level. It includes definitions for command interpreters (shells), standard utility programs, programming interfaces, and system services primarily aimed at application developers and system implementers.

Released in 2025 and maintained by The Open Group and the IEEE Computer Society, POSIX.1-2024 (Issue 8) supersedes the 2009 edition and its successive corrigenda to reflect modern computing needs. This standard emphasizes external operating system characteristics essential for commercial and industrial applications, ensuring interoperability and consistency across diverse platforms.

Key Topics

• Standard Operating System Interface
  Defines the application programming interfaces (APIs) that provide uniform access to system resources, facilitating source-level application portability.

• Command Interpreter and Utilities
  Specifies a standard shell environment and sets of utility programs to support common system tasks and scripting functionalities.

• System Interfaces and Services
  Details system functions, subroutines, and language bindings-especially for the C programming language-that handle process control, file I/O, error handling, and thread management.

• Base Definitions and Conventions
  Includes common terminology, general utilities behavior, and C-language header definitions essential for developing software aligned with POSIX standards.

• Rationale and Historical Context
  Offers informative explanations about design choices, feature inclusions, and deprecations to assist developers and implementers in understanding the standard’s evolution.

• Scope Exclusions
  This standard does not cover graphics interfaces, database management system interfaces, record-oriented I/O considerations, binary code portability, and system configuration or resource availability.

Applications

ISO/IEC/IEEE 9945:2025 is vital for systems where source code portability is a priority, including:

• Cross-Platform Software Development
  Enables developers to write applications that run consistently on multiple UNIX-like and POSIX-compliant systems without modification.

• Embedded Systems
  Provides standardized interfaces critical for embedded operating systems requiring robust and portable system calls.

• Commercial and Industrial Software
  Ensures predictable system behavior, process control, and error handling mechanisms important for business-critical applications.

• Operating System Implementers
  Acts as a guideline for OS vendors aiming to deliver POSIX-compliant environments that support third-party software compatibility.

• Shell Scripting and Automation
  Standardizes command-line interpreters and utilities for reliable script execution across compliant systems.

Related Standards

• IEEE Std 1003.1™-2024
  The IEEE version of the POSIX standard that aligns with ISO/IEC/IEEE 9945:2025, sharing identical technical content.

• X/Open System Interface (XSI)
  A supplementary interface definition extending POSIX standards focusing on interoperability and extended system features.

• ISO/IEC 9899 (C Programming Language Standard)
  Closely related due to the importance of C in providing system interface definitions and API specifications in POSIX environments.

• The Open Group Base Specifications
  Encompasses the same POSIX requirements as ISO/IEC/IEEE 9945 under The Open Group stewardship emphasizing practical conformity and certification.

Conclusion

ISO/IEC/IEEE FDIS 9945:2025 represents a cornerstone standard for operating system portability, defining robust and consistent APIs, shell behavior, and utility programs. Its broad adoption aids developers and vendors in delivering interoperable and maintainable software across diverse platforms. By adhering to POSIX Base Specifications, organizations enhance software compatibility, reduce development costs, and foster a shared ecosystem of dependable technology solutions.

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Keywords: POSIX® Base Specifications, ISO/IEC/IEEE 9945, portable operating system interface, POSIX.1-2024, system interfaces, operating system standards, application portability, command interpreter, POSIX shell, IEEE Std 1003.1, The Open Group, standard utilities, API portability.

Standards Content (Sample)

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.
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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.
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AND TO PROVIDE SUPPORTING D OCUMENTATION.
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Foreword
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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.
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ISO/IEC/IEEE 9945:2025(en)
Any feedback or questions on this document should be directed to the user’s national standards body. A
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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
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Published 14 June 2024 by IEEE in the United States of America.
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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)
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IEEE Standard for Information Technology—Portable Operating System Interface (POSIX®)
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Steve Bartolomei Richard Hansen Bastien Roucaries
Petr Baudis Guy Harris Daniel Sabogal
Fabrice Bauzac Mark Harris Askar Safin
Eric Blake Gavin Howard Jörg Schilling
Mark S. Brown Elliott Hughes Ed Schouten
Erik Cederstrand Roland Illig Konrad Schwarz
Stéphane Chazelas
Jarmo Jaakkola Ingo Schwarze
Scott Cheloha Andrew Josey Martin Sebor
Alexander Cherepanov Nickolas Raymond Kaczynski Olaf 'Rhialto' Seibert
Geoff Clare Nate Karstens Joel Sherrill
Robert Clausecker Michael Kerrisk Curtis Smith
Daniel Colascione Alexey Khoroshilov Paul Smith
Garrett Cooper
Elad Lahav Job Snijders
Alan Coopersmith Jeff Layton Oliver Soong
Ralph Corderoy Vincent Lefèvre Dimitri Staessens
Ciprian Dorin Craciun Mark Lundblad Nicholas M. Stoughton
Donald W. Cragun Roger Marquis Sören Tempel
Mike Crowe Nikos Mavrogiannopoulos Jilles Tjoelker
Martijn Dekker Davin McCall William Toth
Andrés Delfino Mihail Mihaylov Fred J. Tydeman
D.J. Delorie Todd C. Miller Stijn van Dronrgelen
Matthew Dempsky Christoph Anton Mitterer Lawrence Velázquez
Antonio Diaz Mihai Moldovan Evgeny Vereshchagin
Ulrich Drepper Ed Morton
Rasmus Villemoes
Paul Eggert Joseph S. Myers Dennis Wölfing
Robert Elz Szabolcs Nagy Jonathan Wakely
Steve Emmerson
Jonathan Nieder Colin Watson
Laszlo Ersek Danny Niu Nathan Weeks
Andras Farkas Steffen Nurpmeso Florian Weimer
Richard Felker
Richard Palethorpe Zack Weinberg
Dirk Fieldhouse Daniele Palumbo David A. Wheeler
Mike Frysinger Isabella Parakiss Nicolas Williams
Mark Galeck Ben Pfaff Yousong Zhou
Enrique Garcia J. William Piggott Mark Ziegast
Thorsten Glaser Wayne Pollock Roman Žilka
viii  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
Austin Group Working Group Members
Hans Aberg Jan Hafer Chet Ramey
Eric Ackermann Bruno Haible Gabriel Ravier
Godmar Back Richard Hansen G. Branden Robinson
Eric Blake Mark Harris Eric Sanchis
Volodymyr Boyko David Holland Daniel Santos
Andries E. Brouwer Gavin Howard Jörg Schilling
Mark S. Brown Elliott Hughes
Ed Schouten
Jefferson Carpenter Roland Illig Konrad Schwarz
Olivier Certner Lennart Jablonka Ingo Schwarze
Stéphane Chazelas Chris F.A. Johns
John Scott
Tom Cherry Darrin Johnson Simon Ser
Earl Chew Andrew Josey Joel Sherrill
Geoff Clare Nate Karstens
Thor Lancelot Simon
Joshua M. Clulow Dan Kegel Keld Simonsen
Alan Coopersmith Michael Kerrisk Paul Smith
Donald W. Cragun
Anton Khikhlukha Job Snijders
Mike Crowe Ukko Koknevics Gabriel Soldani
Martijn Dekker Bruce Korb Oliver Soong
Matthew Dempsky David Korn Dimitri Staessens
Drew DeVault Rob Landley Marc J. Stephenson
Casper Dik Vincent Lefèvre Nicholas M. Stoughton
Deepa Dinamani Wojtek Lerch Oskar Sveinsen
Dan Douglas Charlie Lin Alfred M. Szmidt
Niall Douglas Scott Lurndal Tapani Tarvainen
Ulrich Drepper Roger Marquis Alexander Terekhov
Lawrence D.K.B. Dwyer Davin McCall Donn Terry
Paul Eggert Stephen Michell
Jilles Tjoelker
Daniel Eischen Per Mildner Fred J. Tydeman
Julian Elischer Christoph Anton Mitterer O÷uz Uysal
Robert Elz
Thomas Mueller Harald van Dijk
Bruce Evans Wilhelm Mueller Lawrence Velázquez
Richard Felker Koichi Murase Oleksii Vilchansk
Jeffrey K. Fellin
Joseph S. Myers Corinna Vinschen
Dirk Fieldhouse Danny Niu Jonathan Wakely
Hal Finkel Gian Ntzik L.A. Walsh
Michael Forney Steffen Nurpmeso David A. Wheeler
Mike Frysinger Carlos O'Donell Jakub Wilk
Mark Galeck Andrew Pennebaker Dennis Wölfing
Thorsten Glaser Steven Penny Garrett Wollman
Andreas Grapentin Colin Percival Jörg Wunsch
Michael Greenberg J. William Piggott Ryan Zezeski
Philip Guenther Wayne Pollock Mark Ziegast
Joseph M. Gwinn Quentin Rameau Jason Zions
The Open Group
When The Open Group approved the Base Specifications, Issue 8, (technically identical to this standard) on
21 March 2024, the membership of The Open Group Base Working Group was as follows:
Andrew Josey, Chair
Eric Blake, Austin Group Liaison
Cathy Fox, Geoff Clare, Technical Editor
Base Working Group Members
Joe Auricchio Geoff Clare Andrew Josey
Eric Blake Donald W. Cragun Mark Ziegast
© 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
IEEE
At the time this standard was completed, the Microprocessor Committee had the following membership:
Ralph Baker Kearfott, Chair
Leonard Tsai, Vice Chair and P754 Chair
Andrew Josey, P1003.1 Chair
Donald W. Cragun, Austin Group Liaison
Joseph M. Gwinn, Ex-officio Emeritus
Richard Bugg, P1722.1 Chair
Kiran Gunnam, P3109 Chair
David Hough, Outgoing P754 Chair
Dave Olsen, P1722 Chair
Nathalie Revol, P1788 Chair
Blaise Vignon, P3109 Chair
The following members of the individual Standards Association balloting group voted on this standard.
Balloters may have voted for approval, disapproval, or abstention.
Boon Chong Ang Jie Guan Rajesh Murthy
Steven Bezner Joseph M. Gwinn Venkatesha Prasad
Diego Chiozzi Werner Hoelzl Stephen Schwarm
Donald W. Cragun Andrew Josey Walter Struppler
Andrew Fieldsend Piotr Karocki Oren Yuen
David Fuschi Kenneth Lang Janusz Zalewski
When the IEEE SA Standards Board approved this standard on 20 May 2024, it had the following
membership:
David J. Law, Chair
Jon Walter Rosdahl, Vice Chair
Gary Hoffman, Past Chair
Alpesh Shah, Secretary
Sara R. Biyabani Hao Hu Paul Nikolich
Ted Burse Yousef Kimiagar Robby Robson
Stephen Dukes Joseph L. Koepfinger* Lei Wang
Doug Edwards Howard Li F. Keith Waters
J. Travis Griffith Xiaohui Liu Sha Wei
Guido R. Hiertz John Haiying Lu Philip B. Winston
Ronald W Hotchkiss Kevin W. Lu Don Wright
Hiroshi Mano
*Member Emeritus
x  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
Introduction
This introduction is not part of IEEE Std 1003.1™-2024, IEEE Standard for Information Technology—Portable
Operating System Interface (POSIX™)—Base Specifications, Issue 8.
This draft standard was developed, and is maintained, by a joint working group of members of the IEEE
Microprocessor Standards Committee, members of The Open Group, and members of ISO/IEC Joint
Technical Committee 1. This joint working group is known as the Austin Group.
The Austin Group arose out of discussions amongst the parties which started in early 1998, leading to an
initial meeting and formation of the group in September 1998. The purpose of the Austin Group is to develop
and maintain the core open systems interfaces that are the POSIX 1003.1 (and former 1003.2) standards, ®
ISO/IEC 9945, and the core of the Single UNIX Specification.
The approach to specification development has been one of “write once, adopt everywhere”, with the
deliverables being a set of specifications that carry the IEEE POSIX designation, The Open Group Standard
designation, and an ISO/IEC designation.
This unique development has combined both the industry-led efforts and the formal standardization activities
into a single initiative, and included a wide spectrum of participants. The Austin Group continues as the
maintenance body for this document.
Anyone wishing to participate in the Austin Group should contact the chair with their request. There are no
fees for participation or membership. You may participate as an observer or as a contributor. You do not have
to attend face-to-face meetings to participate; electronic participation is most welcome. For more information
on the Austin Group and how to participate, see www.opengroup.org/austin.
Background
The developers of POSIX.1-2024 represent a cross-section of hardware manufacturers, vendors of operating
systems and other software development tools, software designers, consultants, academics, authors,
applications programmers, and others.
Conceptually, POSIX.1-2024 describes a set of fundamental services needed for the efficient construction of
application programs. Access to these services has been provided by defining an interface, using the C
programming language, a command interpreter, and common utility programs that establish standard
semantics and syntax. Since this interface enables application developers to write portable applications – it
was developed with that goal in mind – it has been designated POSIX, an acronym for Portable Operating
System Interface.
Although originated to refer to the original IEEE Std 1003.1-1988, the name POSIX more correctly refers to
a family of related standards: IEEE Std 1003.n and the parts of ISO/IEC 9945. In earlier editions of the IEEE
Standard, the term POSIX was used as a synonym for IEEE Std 1003.1-1988. A preferred term, POSIX.1,
emerged. This maintained the advantages of readability of the symbol “POSIX” without being ambiguous
with the POSIX family of standards.
The Austin Group is named after the location of the inaugural meeting held at the IBM facility in Austin, Texas in September 1998.
The name POSIX was suggested by Richard Stallman. It is expected to be pronounced with the first two syllables as in positive, not
poh-six, or other variations. The pronunciation has been published in an attempt to promulgate a standardized way of referring to
a standard operating system interface.
© 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
Audience
The intended audience for POSIX.1-2024 is all persons concerned with an industry-wide standard operating
system based on the UNIX system. This includes at least four groups of people:
x Persons buying hardware and software systems
x Persons managing companies that are deciding on future corporate computing directions
x Persons implementing operating systems, and especially
x Persons developing applications where portability is an objective
Purpose
Several principles guided the development of POSIX.1-2024:
x Application-Oriented – The basic goal was to promote portability of application programs across
UNIX system environments by developing a clear, consistent, and unambiguous standard for the
interface specification of a portable operating system based on the UNIX system documentation.
POSIX.1-2024 codifies the common, existing definition of the UNIX system.
x Interface, Not Implementation – POSIX.1-2024 defines an interface, not an implementation. No
distinction is made between library functions and system calls; both are referred to as functions. No
details of the implementation of any function are given (although historical practice is sometimes
indicated in the RATIONALE section). Symbolic names are given for constants (such as signals and
error numbers) rather than numbers.
x Source, Not Object, Portability – POSIX.1-2024 has been written so that a program written and
translated for execution on one conforming implementation may also be translated for execution on
another conforming implementation. POSIX.1-2024 does not guarantee that executable (object or
binary) code will execute under a different conforming implementation than that for which it was
translated, even if the underlying hardware is identical.
x The C Language – The system interfaces and header definitions are written in terms of the standard
C language as specified in the ISO C standard.
x No Superuser, No System Administration – There was no intention to specify all aspects of an
operating system. System administration facilities and functions are excluded from this standard,
and functions usable only by the superuser have not been included. Still, an implementation of the
standard interface may also implement features not in POSIX.1-2024. POSIX.1-2024 is also not
concerned with hardware constraints or system maintenance.
x Minimal Interface, Minimally Defined – In keeping with the historical design principles of the
UNIX system, the mandatory core facilities of POSIX.1-2024 have been kept as minimal as
possible. Additional capabilities have been added as optional extensions.
x Broadly Implementable – The developers of POSIX.1-2024 endeavored to make all specified
functions implementable across a wide range of existing and potential systems, including:
— All of the current major systems that are ultimately derived from the original UNIX
system code (Version 7 or later)
— Compatible systems that are not derived from the original UNIX system code
— Emulations hosted on entirely different operating systems
— Networked systems
— Distributed systems
xii  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

— Systems running on a broad range of hardware
No direct references to this goal appear in POSIX.1-2024, but some results of it are mentioned in the
Rationale (Informative) volume.
x Minimal Changes to Historical Implementations – When the original version – IEEE Std 1003.1-
1988 – was published, there were no known historical implementations that did not have to change.
However, there was a broad consensus on a set of functions, types, definitions, and concepts that
formed an interface that was common to most historical implementations.
The adoption of the 1988 and 1990 IEEE system interface standards, the 1992 IEEE shell and
utilities standard, the various The Open Group (formerly X/Open) specifications, and IEEE Std
1003.1-2001 and its technical corrigenda have consolidated this consensus, and this version reflects
the significantly increased level of consensus arrived at since the original versions. The authors of
the original versions tried, as much as possible, to follow the principles below when creating new
specifications:
— By standardizing an interface like one in an historical implementation; for example,
directories
— By specifying an interface that is readily implementable in terms of, and backwards-
compatible with, historical implementations, such as the extended tar format defined in the pax
utility
— By specifying an interface that, when added to an historical implementation, will not
conflict with it; for example, the sigaction() function

POSIX.1-2024 is specifically not a codification of a particular vendor’s product.
It should be noted that implementations will have different kinds of extensions. Some will reflect
“historical usage” and will be preserved for execution of pre-existing applications. These functions
should be considered “obsolescent” and the standard functions used for new applications. Some
extensions will represent functions beyond the scope of POSIX.1-2024. These need to be used with
careful management to be able to adapt to future extensions of POSIX.1-2024 and/or port to
implementations that provide these services in a different manner.
x Minimal Changes to Existing Application Code—A goal of POSIX.1-2024 was to minimize
addi
...