standards(7) Miscellaneous Information Manual standards(7)
NAME
standards - C and UNIX Standards
DESCRIPTION
The STANDARDS section that appears in many manual pages identifies var-
ious standards to which the documented interface conforms. The follow-
ing list briefly describes these standards.
V7 Version 7 (also known as Seventh Edition) UNIX, released by
AT&T/Bell Labs in 1979. After this point, UNIX systems diverged
into two main dialects: BSD and System V.
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 ver-
sion 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 consid-
ered the definitive System V release.
SVID 4 System V Interface Definition version 4, issued in 1995. Avail-
able online at ]8;;http://www.sco.com/developers/devspecs/\http://www.sco.com/developers/devspecs/]8;;\.
C89 This was the first C language standard, ratified by ANSI (Ameri-
can National Standards Institute) in 1989 (X3.159-1989). Some-
times this is known as ANSI C, but since C99 is also an ANSI
standard, this term is ambiguous. This standard was also rati-
fied 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
]8;;http://www.open-std.org/jtc1/sc22/wg14/www/standards\http://www.open-std.org/jtc1/sc22/wg14/www/standards]8;;\.
C11 This revision of the C language standard was ratified by ISO in
2011 (ISO/IEC 9899:2011).
LFS The Large File Summit specification, completed in 1996. This
specification defined mechanisms that allowed 32-bit systems to
support the use of large files (i.e., 64-bit file offsets). See
]8;;https://www.opengroup.org/platform/lfs.html\https://www.opengroup.org/platform/lfs.html]8;;\.
POSIX.1-1988
This was the first POSIX standard, ratified by IEEE as IEEE Std
1003.1-1988, and subsequently adopted (with minor revisions) as
an ISO standard in 1990. The term "POSIX" was coined by Richard
Stallman.
POSIX.1-1990
"Portable Operating System Interface for Computing Environ-
ments". IEEE 1003.1-1990 part 1, ratified by ISO in 1990
(ISO/IEC 9945-1:1990).
POSIX.2
IEEE Std 1003.2-1992, describing commands and utilities, rati-
fied 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).
POSIX.1c (formerly known as POSIX.4a)
IEEE Std 1003.1c-1995, which describes the POSIX threads inter-
faces.
POSIX.1d
IEEE Std 1003.1d-1999, which describes additional real-time ex-
tensions.
POSIX.1g
IEEE Std 1003.1g-2000, which describes networking APIs (includ-
ing sockets).
POSIX.1j
IEEE Std 1003.1j-2000, which describes advanced real-time exten-
sions.
POSIX.1-1996
A 1996 revision of POSIX.1 which incorporated POSIX.1b and
POSIX.1c.
XPG3 Released in 1989, this was the first release of the X/Open
Portability Guide to be based on a POSIX standard
(POSIX.1-1988). This multivolume guide was developed by the
X/Open Group, a multivendor consortium.
XPG4 A revision of the X/Open Portability Guide, released in 1992.
This revision incorporated POSIX.2.
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
(incorrectly) as XPG5. This standard appeared in 1997. Systems
conforming to this standard can be branded UNIX 98. See also
]8;;http://www.unix.org/version2/\http://www.unix.org/version2/]8;;\.)
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 un-
der the auspices of the Austin Group ]8;;http://www.opengroup.org/austin/\http://www.opengroup.org
/austin/]8;;\. The standard is available online at
]8;;http://www.unix.org/version3/\http://www.unix.org/version3/]8;;\.
The standard defines two levels of conformance: POSIX confor-
mance, which is a baseline set of interfaces required of a con-
forming system; and XSI Conformance, which additionally mandates
a set of interfaces (the "XSI extension") which are only op-
tional for POSIX conformance. XSI-conformant systems can be
branded UNIX 03.
The POSIX.1-2001 document is broken into four parts:
XBD: Definitions, terms, and concepts, header file specifica-
tions.
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.
The Single UNIX Specification version 3 (SUSv3) comprises the
Base Specifications containing XBD, XSH, XCU, and XRAT as above,
plus X/Open Curses Issue 4 version 2 as an extra volume that is
not in POSIX.1-2001.
Two Technical Corrigenda (minor fixes and improvements) of the
original 2001 standard have occurred: TC1 in 2003 and TC2 in
2004.
POSIX.1-2008
SUSv4 Work on the next revision of POSIX.1/SUS was completed and rati-
fied in 2008. The standard is available online at
]8;;http://www.unix.org/version4/\http://www.unix.org/version4/]8;;\.
The changes in this revision are not as large as those that oc-
curred 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 2008 revision of the stan-
dard. A few interfaces that are present in POSIX.1-2001 are
marked as obsolete in POSIX.1-2008, or removed from the standard
altogether.
The revised standard is structured in the same way as its prede-
cessor. The Single UNIX Specification version 4 (SUSv4) com-
prises the Base Specifications containing XBD, XSH, XCU, and
XRAT, plus X/Open Curses Issue 7 as an extra volume that is not
in POSIX.1-2008.
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 STANDARDS 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.
Technical Corrigendum 1 (minor fixes and improvements) of this
standard was released in 2013.
Technical Corrigendum 2 of this standard was released in 2016.
Further information can be found on the Austin Group web site,
]8;;http://www.opengroup.org/austin/\http://www.opengroup.org/austin/]8;;\.
SUSv4 2016 edition
This is equivalent to POSIX.1-2008, with the addition of Techni-
cal Corrigenda 1 and 2 and the XCurses specification.
POSIX.1-2017
This revision of POSIX is technically identical to POSIX.1-2008
with Technical Corrigenda 1 and 2 applied.
SUSv4 2018 edition
This is equivalent to POSIX.1-2017, with the addition of the
XCurses specification.
The interfaces documented in POSIX.1/SUS are available as manual pages
under sections 0p (header files), 1p (commands), and 3p (functions);
thus one can write "man 3p open".
SEE ALSO
getconf(1), confstr(3), pathconf(3), sysconf(3), attributes(7), fea-
ture_test_macros(7), libc(7), posixoptions(7), system_data_types(7)
Linux man-pages 6.7 2023-10-31 standards(7)
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