man > standards(7)

standards(7)                      Miscellaneous Information Manual                      standards(7)

NAME
       standards - C and UNIX Standards

DESCRIPTION
       The STANDARDS 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  (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 version 2 (SVID 2).

       System V release 4 (SVr4)
              This  was  the  successor  to SVr3, released in 1989.  This version of System V is de‐
              scribed in the "Programmer's Reference Manual: Operating  System  API  (Intel  proces‐
              sors)" (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
              ]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 (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 occa‐
              sionally 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 sub‐
              sequently 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  Environments".   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, 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).

       POSIX.1c (formerly known as POSIX.4a)
              IEEE Std 1003.1c-1995, which describes the POSIX threads interfaces.

       POSIX.1d
              IEEE Std 1003.1d-1999, which describes additional real-time extensions.

       POSIX.1g
              IEEE Std 1003.1g-2000, which describes networking APIs (including sockets).

       POSIX.1j
              IEEE Std 1003.1j-2000, which describes 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 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 incorpo‐
              rated 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 stan‐
              dards (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  under  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 conformance, which is a baseline
              set of interfaces required of a conforming system; and XSI  Conformance,  which  addi‐
              tionally  mandates  a  set of interfaces (the "XSI extension") which are only optional
              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 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.

              The Single UNIX Specification version 3 (SUSv3) comprises the Base Specifications con‐
              taining 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  ratified  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  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 2008 revision of the standard.  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  predecessor.   The  Single
              UNIX Specification version 4 (SUSv4) comprises 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.open‐
              group.org/austin/]8;;\.

       SUSv4 2016 edition
              This is equivalent to POSIX.1-2008, with the addition of Technical Corrigenda 1 and  2
              and the XCurses specification.

       POSIX.1-2017
              This  revision of POSIX is technically identical to POSIX.1-2008 with Technical Corri‐
              genda 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),  feature_test_macros(7),
       libc(7), posixoptions(7), system_data_types(7)

Linux man-pages 6.7                          2023-10-31                                 standards(7)