NAME | DESCRIPTION | SEE ALSO | COLOPHON
STANDARDS(7) Linux Programmer's Manual STANDARDS(7)
standards - C and UNIX Standards
The CONFORMING TO section that appears in many manual pages identifies various
standards to which the documented interface conforms. The following list
briefly describes these standards.
V7 Version 7, the ancestral UNIX from Bell Labs.
4.2BSD This is an implementation standard defined by the 4.2 release of the
Berkeley Software Distribution, released by the University of
California at Berkeley. This was the first Berkeley release that
contained a TCP/IP stack and the sockets API. 4.2BSD was released in
1983.
Earlier major BSD releases included 3BSD (1980), 4BSD (1980), and
4.1BSD (1981).
4.3BSD The successor to 4.2BSD, released in 1986.
4.4BSD The successor to 4.3BSD, released in 1993. This was the last major
Berkeley release.
System V
This is an implementation standard defined by AT&T's milestone 1983
release of its commercial System V (five) release. The previous major
AT&T release was System III, released in 1981.
System V release 2 (SVr2)
This was the next System V release, made in 1985. The SVr2 was
formally described in the System V Interface Definition version 1 (SVID
1) published in 1985.
System V release 3 (SVr3)
This was the successor to SVr2, released in 1986. This release was
formally described in the System V Interface Definition version 2 (SVID
2).
System V release 4 (SVr4)
This was the successor to SVr3, released in 1989. This version of
System V is described in the "Programmer's Reference Manual: Operating
System API (Intel processors)" (Prentice-Hall 1992, ISBN 0-13-951294-2)
This release was formally described in the System V Interface
Definition version 3 (SVID 3), and is considered the definitive System
V release.
SVID 4 System V Interface Definition version 4, issued in 1995. Available
online at http://www.sco.com/developers/devspecs/ .
C89 This was the first C language standard, ratified by ANSI (American
National Standards Institute) in 1989 (X3.159-1989). Sometimes this is
known as ANSI C, but since C99 is also an ANSI standard, this term is
ambiguous. This standard was also ratified by ISO (International
Standards Organization) in 1990 (ISO/IEC 9899:1990), and is thus
occasionally referred to as ISO C90.
C99 This revision of the C language standard was ratified by ISO in 1999
(ISO/IEC 9899:1999). Available online at http://www.open-
std.org/jtc1/sc22/wg14/www/standards.
POSIX.1-1990
"Portable Operating System Interface for Computing Environments". IEEE
1003.1-1990 part 1, ratified by ISO in 1990 (ISO/IEC 9945-1:1990).
Further information can be found in Donald Lewine's "POSIX Programmer's
Guide" (O'Reilly & Associates, Inc., 1991, ISBN 0-937175-73-0). The
term "POSIX" was coined by Richard Stallman.
POSIX.2
IEEE Std 1003.2-1992, describing commands and utilities, ratified by
ISO in 1993 (ISO/IEC 9945-2:1993).
POSIX.1b (formerly known as POSIX.4)
IEEE Std 1003.1b-1993 describing real-time facilities for portable
operating systems, ratified by ISO in 1996 (ISO/IEC 9945-1:1996). For
further information, see "POSIX.4: Programming for the real world" by
Bill O. Gallmeister (O'Reilly & Associates, Inc. ISBN 1-56592-074-0).
POSIX.1c
IEEE Std 1003.1c-1995 describing the POSIX threads interfaces.
POSIX.1d
IEEE Std 1003.1c-1999 describing additional real-time extensions.
POSIX.1g
IEEE Std 1003.1g-2000 describing networking APIs (including sockets).
POSIX.1j
IEEE Std 1003.1j-2000 describing advanced real-time extensions.
POSIX.1-1996
A 1996 revision of POSIX.1 which incorporated POSIX.1b and POSIX.1c.
XPG3 Released in 1989, this was the first significant release of the X/Open
Portability Guide, produced by the X/Open Company, a multi-vendor
consortium. This multi-volume guide was based on the POSIX standards.
XPG4 A revision of the X/Open Portability Guide, released in 1992.
XPG4v2 A 1994 revision of XPG4. This is also referred to as Spec 1170, where
1170 referred to the number of interfaces defined by this standard.
SUS (SUSv1)
Single UNIX Specification. This was a repackaging of XPG4v2 and other
X/Open standards (X/Open Curses Issue 4 version 2, X/Open Networking
Service (XNS) Issue 4). Systems conforming to this standard can be
branded UNIX 95.
SUSv2 Single UNIX Specification version 2. Sometimes also referred to as
XPG5. This standard appeared in 1997. Systems conforming to this
standard can be branded UNIX 98. See also http://www.UNIX-
systems.org/version2/ .)
POSIX.1-2001, SUSv3
This was a 2001 revision and consolidation of the POSIX.1, POSIX.2, and
SUS standards into a single document, conducted under the auspices of
the Austin group (http://www.opengroup.org/austin/ .) The standard is
available online at http://www.unix-systems.org/version3/ , and the
interfaces that it describes are also available in the Linux manual
pages package under sections 1p and 3p (e.g., "man 3p open").
The standard defines two levels of conformance: POSIX conformance,
which is a baseline set of interfaces required of a conforming system;
and XSI Conformance, which additionally mandates a set of interfaces
(the "XSI extension") which are only optional for POSIX conformance.
XSI-conformant systems can be branded UNIX 03. (XSI conformance
constitutes the Single UNIX Specification version 3 (SUSv3).)
The POSIX.1-2001 document is broken into four parts:
XBD: Definitions, terms and concepts, header file specifications.
XSH: Specifications of functions (i.e., system calls and library
functions in actual implementations).
XCU: Specifications of commands and utilities (i.e., the area formerly
described by POSIX.2).
XRAT: Informative text on the other parts of the standard.
POSIX.1-2001 is aligned with C99, so that all of the library functions
standardized in C99 are also standardized in POSIX.1-2001.
Two Technical Corrigenda (minor fixes and improvements) of the original
2001 standard have occurred: TC1 in 2003 (referred to as POSIX.1-2003),
and TC2 in 2004 (referred to as POSIX.1-2004).
POSIX.1-200x, SUSv4
Work on the next revision of POSIX.1/SUS is near completion. The
balloting on the revision is expected to be completed in 2008, so that
the revision is likely to be named POSIX.1-2008.
The changes in this revision are not as large as those that occurred
for POSIX.1-2001/SUSv3, but a number of new interfaces are added and
various details of existing specifications are modified. Many of the
interfaces that were optional in POSIX.1-2001 become mandatory in the
next revision of the standard. A few interfaces that are present in
POSIX.1-2001 are marked as obsolete in POSIX.1-2001, or removed from
the standard altogether.
The revised standard is broken into the same four parts as
POSIX.1-2001, and again there are two levels of conformance: the
baseline POSIX Conformance, and XSI Conformance, which mandates an
additional set of interfaces beyond those in the base specification.
In general, where the CONFORMING TO section of a manual page lists
POSIX.1-2001, it can be assumed that the interface also conforms to
POSIX.1-2008, unless otherwise noted.
Further information can be found on the Austin group web site,
http://www.opengroup.org/austin/ .
feature_test_macros(7), posixoptions(7)
This page is part of release 3.08 of the Linux man-pages project. A
description of the project, and information about reporting bugs, can be found
at http://www.kernel.org/doc/man-pages/.
Linux 2008-08-07 STANDARDS(7)