1STANDARDS(7)               Linux Programmer's Manual              STANDARDS(7)
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NAME

6       standards - C and UNIX Standards
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DESCRIPTION

9       The  CONFORMING TO section that appears in many manual pages identifies
10       various standards to which the documented interface conforms.  The fol‐
11       lowing list briefly describes these standards.
12
13       V7     Version  7  (also  known  as  Seventh Edition) UNIX, released by
14              AT&T/Bell Labs in 1979.  After this point, UNIX systems diverged
15              into two main dialects: BSD and System V.
16
17       4.2BSD This is an implementation standard defined by the 4.2 release of
18              the Berkeley Software Distribution, released by  the  University
19              of  California at Berkeley.  This was the first Berkeley release
20              that contained a TCP/IP stack and the sockets API.   4.2BSD  was
21              released in 1983.
22
23              Earlier  major  BSD  releases included 3BSD (1980), 4BSD (1980),
24              and 4.1BSD (1981).
25
26       4.3BSD The successor to 4.2BSD, released in 1986.
27
28       4.4BSD The successor to 4.3BSD, released in 1993.  This  was  the  last
29              major Berkeley release.
30
31       System V
32              This  is  an implementation standard defined by AT&T's milestone
33              1983 release of its commercial System  V  (five)  release.   The
34              previous major AT&T release was System III, released in 1981.
35
36       System V release 2 (SVr2)
37              This  was the next System V release, made in 1985.  The SVr2 was
38              formally described in the System V Interface Definition  version
39              1 (SVID 1) published in 1985.
40
41       System V release 3 (SVr3)
42              This  was the successor to SVr2, released in 1986.  This release
43              was formally described in the System V Interface Definition ver‐
44              sion 2 (SVID 2).
45
46       System V release 4 (SVr4)
47              This  was the successor to SVr3, released in 1989.  This version
48              of System V is described in the "Programmer's Reference  Manual:
49              Operating  System  API  (Intel processors)" (Prentice-Hall 1992,
50              ISBN 0-13-951294-2) This release was formally described  in  the
51              System V Interface Definition version 3 (SVID 3), and is consid‐
52              ered the definitive System V release.
53
54       SVID 4 System V Interface Definition version 4, issued in 1995.  Avail‐
55              able online at ⟨http://www.sco.com/developers/devspecs/⟩.
56
57       C89    This was the first C language standard, ratified by ANSI (Ameri‐
58              can National Standards Institute) in 1989 (X3.159-1989).   Some‐
59              times  this  is  known  as ANSI C, but since C99 is also an ANSI
60              standard, this term is ambiguous.  This standard was also  rati‐
61              fied  by  ISO  (International  Standards  Organization)  in 1990
62              (ISO/IEC 9899:1990), and is thus occasionally referred to as ISO
63              C90.
64
65       C99    This  revision of the C language standard was ratified by ISO in
66              1999    (ISO/IEC    9899:1999).      Available     online     at
67http://www.open-std.org/jtc1/sc22/wg14/www/standards⟩.
68
69       C11    This  revision of the C language standard was ratified by ISO in
70              2011 (ISO/IEC 9899:2011).
71
72       POSIX.1-1990
73              "Portable Operating  System  Interface  for  Computing  Environ‐
74              ments".   IEEE  1003.1-1990  part  1,  ratified  by  ISO in 1990
75              (ISO/IEC 9945-1:1990).  The term "POSIX" was coined  by  Richard
76              Stallman.
77
78       POSIX.2
79              IEEE  Std  1003.2-1992, describing commands and utilities, rati‐
80              fied by ISO in 1993 (ISO/IEC 9945-2:1993).
81
82       POSIX.1b (formerly known as POSIX.4)
83              IEEE Std 1003.1b-1993, describing real-time facilities for  por‐
84              table  operating  systems,  ratified  by  ISO  in  1996 (ISO/IEC
85              9945-1:1996).
86
87       POSIX.1c
88              IEEE Std 1003.1c-1995, which describes the POSIX threads  inter‐
89              faces.
90
91       POSIX.1d
92              IEEE  Std  1003.1c-1999,  which  describes  additional real-time
93              extensions.
94
95       POSIX.1g
96              IEEE Std 1003.1g-2000, which describes networking APIs  (includ‐
97              ing sockets).
98
99       POSIX.1j
100              IEEE Std 1003.1j-2000, which describes advanced real-time exten‐
101              sions.
102
103       POSIX.1-1996
104              A 1996 revision  of  POSIX.1  which  incorporated  POSIX.1b  and
105              POSIX.1c.
106
107       XPG3   Released  in 1989, this was the first significant release of the
108              X/Open Portability Guide, produced by the X/Open Company, a mul‐
109              tivendor  consortium.   This  multivolume guide was based on the
110              POSIX standards.
111
112       XPG4   A revision of the X/Open Portability Guide, released in 1992.
113
114       XPG4v2 A 1994 revision of XPG4.  This is also referred to as Spec 1170,
115              where  1170 referred to the number of interfaces defined by this
116              standard.
117
118       SUS (SUSv1)
119              Single UNIX Specification.  This was a repackaging of XPG4v2 and
120              other  X/Open standards (X/Open Curses Issue 4 version 2, X/Open
121              Networking Service (XNS) Issue 4).  Systems conforming  to  this
122              standard can be branded UNIX 95.
123
124       SUSv2  Single UNIX Specification version 2.  Sometimes also referred to
125              as XPG5.  This standard appeared in 1997.  Systems conforming to
126              this    standard   can   be   branded   UNIX   98.    See   also
127http://www.UNIX-systems.org/version2/⟩.)
128
129       POSIX.1-2001, SUSv3
130              This was a 2001  revision  and  consolidation  of  the  POSIX.1,
131              POSIX.2,  and  SUS  standards  into a single document, conducted
132              under the auspices of the Austin Group ⟨http://www.opengroup.org
133              /austin/⟩.     The    standard    is    available    online   at
134http://www.unix-systems.org/version3/⟩, and the interfaces that
135              it  describes are also available in the Linux manual pages pack‐
136              age under sections 1p and 3p (e.g., "man 3p open").
137
138              The standard defines two levels of  conformance:  POSIX  confor‐
139              mance,  which is a baseline set of interfaces required of a con‐
140              forming system; and XSI Conformance, which additionally mandates
141              a  set  of  interfaces  (the  "XSI  extension")  which  are only
142              optional for POSIX conformance.  XSI-conformant systems  can  be
143              branded  UNIX  03.  (XSI conformance constitutes the Single UNIX
144              Specification version 3 (SUSv3).)
145
146              The POSIX.1-2001 document is broken into four parts:
147
148              XBD: Definitions, terms and  concepts,  header  file  specifica‐
149              tions.
150
151              XSH: Specifications of functions (i.e., system calls and library
152              functions in actual implementations).
153
154              XCU: Specifications of commands and utilities  (i.e.,  the  area
155              formerly described by POSIX.2).
156
157              XRAT: Informative text on the other parts of the standard.
158
159              POSIX.1-2001  is  aligned  with  C99, so that all of the library
160              functions  standardized  in  C99  are   also   standardized   in
161              POSIX.1-2001.
162
163              Two  Technical  Corrigenda (minor fixes and improvements) of the
164              original 2001 standard have occurred: TC1 in 2003 (also known as
165              POSIX.1-2003), and TC2 in 2004 (also known as POSIX.1-2004).
166
167       POSIX.1-2008, SUSv4
168              Work on the next revision of POSIX.1/SUS was completed and rati‐
169              fied in 2008.
170
171              The changes in this revision are not  as  large  as  those  that
172              occurred  for POSIX.1-2001/SUSv3, but a number of new interfaces
173              are added and various details  of  existing  specifications  are
174              modified.    Many  of  the  interfaces  that  were  optional  in
175              POSIX.1-2001 become mandatory in the 2008 revision of the  stan‐
176              dard.   A  few  interfaces  that are present in POSIX.1-2001 are
177              marked as obsolete in POSIX.1-2008, or removed from the standard
178              altogether.
179
180              The  revised  standard  is  broken  into  the same four parts as
181              POSIX.1-2001, and again there are two levels of conformance: the
182              baseline  POSIX Conformance, and XSI Conformance, which mandates
183              an additional set of interfaces beyond those in the base  speci‐
184              fication.
185
186              In  general,  where  the  CONFORMING TO section of a manual page
187              lists POSIX.1-2001, it can be assumed that  the  interface  also
188              conforms to POSIX.1-2008, unless otherwise noted.
189
190              Technical  Corrigendum  1 (minor fixes and improvements) of this
191              standard was released in 2013 (also known as POSIX.1-2013).
192
193              Technical Corrigendum 2 of this standard was  released  in  2016
194              (also known as POSIX.1-2016).
195
196              Further  information  can be found on the Austin Group web site,
197http://www.opengroup.org/austin/⟩.
198

SEE ALSO

200       getconf(1), confstr(3), pathconf(3),  sysconf(3),  attributes(7),  fea‐
201       ture_test_macros(7), libc(7), posixoptions(7)
202

COLOPHON

204       This  page  is  part of release 4.16 of the Linux man-pages project.  A
205       description of the project, information about reporting bugs,  and  the
206       latest     version     of     this    page,    can    be    found    at
207       https://www.kernel.org/doc/man-pages/.
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211Linux                             2017-11-26                      STANDARDS(7)
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