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24 .TH STANDARDS 7 2020-11-01 "Linux" "Linux Programmer's Manual"
25 .SH NAME
26 standards \- C and UNIX Standards
27 .SH DESCRIPTION
28 The CONFORMING TO section that appears in many manual pages identifies
29 various standards to which the documented interface conforms.
30 The following list briefly describes these standards.
31 .TP
32 .B V7
33 Version 7 (also known as Seventh Edition) UNIX,
34 released by AT&T/Bell Labs in 1979.
35 After this point, UNIX systems diverged into two main dialects:
36 BSD and System V.
37 .TP
38 .B 4.2BSD
39 This is an implementation standard defined by the 4.2 release
40 of the
41 .IR "Berkeley Software Distribution",
42 released by the University of California at Berkeley.
43 This was the first Berkeley release that contained a TCP/IP
44 stack and the sockets API.
45 4.2BSD was released in 1983.
46 .IP
47 Earlier major BSD releases included
48 .IR 3BSD
49 (1980),
50 .I 4BSD
51 (1980),
52 and
53 .I 4.1BSD
54 (1981).
55 .TP
56 .B 4.3BSD
57 The successor to 4.2BSD, released in 1986.
58 .TP
59 .B 4.4BSD
60 The successor to 4.3BSD, released in 1993.
61 This was the last major Berkeley release.
62 .TP
63 .B System V
64 This is an implementation standard defined by AT&T's milestone 1983
65 release of its commercial System V (five) release.
66 The previous major AT&T release was
67 .IR "System III" ,
68 released in 1981.
69 .TP
70 .B System V release 2 (SVr2)
71 This was the next System V release, made in 1985.
72 The SVr2 was formally described in the
73 .I "System V Interface Definition version 1"
74 .RI ( "SVID 1" )
75 published in 1985.
76 .TP
77 .B System V release 3 (SVr3)
78 This was the successor to SVr2, released in 1986.
79 This release was formally described in the
80 .I "System V Interface Definition version 2"
81 .RI ( "SVID 2" ).
82 .TP
83 .B System V release 4 (SVr4)
84 This was the successor to SVr3, released in 1989.
85 This version of System V is described in the "Programmer's Reference
86 Manual: Operating System API (Intel processors)" (Prentice-Hall
87 1992, ISBN 0-13-951294-2)
88 This release was formally described in the
89 .I "System V Interface Definition version 3"
90 .RI ( "SVID 3" ),
91 and is considered the definitive System V release.
92 .TP
93 .B SVID 4
94 System V Interface Definition version 4, issued in 1995.
95 Available online at
96 .UR http://www.sco.com\:/developers\:/devspecs/
97 .UE .
98 .TP
99 .B C89
100 This was the first C language standard, ratified by ANSI
101 (American National Standards Institute) in 1989
102 .RI ( X3.159-1989 ).
103 Sometimes this is known as
104 .IR "ANSI C" ,
105 but since C99 is also an
106 ANSI standard, this term is ambiguous.
107 This standard was also ratified by
108 ISO (International Standards Organization) in 1990
109 .RI ( "ISO/IEC 9899:1990" ),
110 and is thus occasionally referred to as
111 .IR "ISO C90" .
112 .TP
113 .B C99
114 This revision of the C language standard was ratified by ISO in 1999
115 .RI ( "ISO/IEC 9899:1999" ).
116 Available online at
117 .UR http://www.open\-std.org\:/jtc1\:/sc22\:/wg14\:/www\:/standards
118 .UE .
119 .TP
120 .B C11
121 This revision of the C language standard was ratified by ISO in 2011
122 .RI ( "ISO/IEC 9899:2011" ).
123 .IP
124 .B LFS
125 The Large File Summit specification, completed in 1996.
126 This specification defined mechanisms that allowed 32-bit systems
127 to support the use of large files (i.e., 64-bit file offsets).
128 See
129 .UR https://www.opengroup.org\:/platform\:/lfs.html
130 .UE .
131 .TP
132 .B POSIX.1-1988
133 This was the first POSIX standard,
134 ratified by IEEE as IEEE Std 1003.1-1988,
135 and subsequently adopted (with minor revisions) as an ISO standard in 1990.
136 The term "POSIX" was coined by Richard Stallman.
137 .TP
138 .B POSIX.1-1990
139 "Portable Operating System Interface for Computing Environments".
140 IEEE 1003.1-1990 part 1, ratified by ISO in 1990
141 .RI ( "ISO/IEC 9945-1:1990" ).
142 .TP
143 .B POSIX.2
144 IEEE Std 1003.2-1992,
145 describing commands and utilities, ratified by ISO in 1993
146 .RI ( "ISO/IEC 9945-2:1993" ).
147 .TP
148 .BR POSIX.1b " (formerly known as \fIPOSIX.4\fP)"
149 IEEE Std 1003.1b-1993,
150 describing real-time facilities
151 for portable operating systems, ratified by ISO in 1996
152 .RI ( "ISO/IEC 9945-1:1996" ).
153 .TP
154 .B POSIX.1c " (formerly known as \fIPOSIX.4a\fP)"
155 IEEE Std 1003.1c-1995, which describes the POSIX threads interfaces.
156 .TP
157 .BR POSIX.1d
158 IEEE Std 1003.1c-1999, which describes additional real-time extensions.
159 .TP
160 .B POSIX.1g
161 IEEE Std 1003.1g-2000, which describes networking APIs (including sockets).
162 .TP
163 .B POSIX.1j
164 IEEE Std 1003.1j-2000, which describes advanced real-time extensions.
165 .TP
166 .B POSIX.1-1996
167 A 1996 revision of POSIX.1 which incorporated POSIX.1b and POSIX.1c.
168 .TP
169 .B XPG3
170 Released in 1989, this was the first release of the X/Open
171 Portability Guide to be based on a POSIX standard (POSIX.1-1988).
172 This multivolume guide was developed by the X/Open Group,
173 a multivendor consortium.
174 .TP
175 .B XPG4
176 A revision of the X/Open Portability Guide, released in 1992.
177 This revision incorporated POSIX.2.
178 .TP
179 .B XPG4v2
180 A 1994 revision of XPG4.
181 This is also referred to as
182 .IR "Spec 1170" ,
183 where 1170 referred to the number of interfaces
184 defined by this standard.
185 .TP
186 .B "SUS (SUSv1)"
187 Single UNIX Specification.
188 This was a repackaging of XPG4v2 and other X/Open standards
189 (X/Open Curses Issue 4 version 2,
190 X/Open Networking Service (XNS) Issue 4).
191 Systems conforming to this standard can be branded
192 .IR "UNIX 95" .
193 .TP
194 .B SUSv2
195 Single UNIX Specification version 2.
196 Sometimes also referred to (incorrectly) as
197 .IR XPG5 .
198 This standard appeared in 1997.
199 Systems conforming to this standard can be branded
200 .IR "UNIX 98" .
201 See also
202 .UR http://www.unix.org\:/version2/
203 .UE .)
204 .TP
205 .B POSIX.1-2001, SUSv3
206 This was a 2001 revision and consolidation of the
207 POSIX.1, POSIX.2, and SUS standards into a single document,
208 conducted under the auspices of the Austin Group
209 .UR http://www.opengroup.org\:/austin/
210 .UE .
211 The standard is available online at
212 .UR http://www.unix.org\:/version3/
213 .UE .
214 .IP
215 The standard defines two levels of conformance:
216 .IR "POSIX conformance" ,
217 which is a baseline set of interfaces required of a conforming system;
218 and
219 .IR "XSI Conformance",
220 which additionally mandates a set of interfaces
221 (the "XSI extension") which are only optional for POSIX conformance.
222 XSI-conformant systems can be branded
223 .IR "UNIX 03" .
224 .IP
225 The POSIX.1-2001 document is broken into four parts:
226 .IP
227 .BR XBD :
228 Definitions, terms, and concepts, header file specifications.
229 .IP
230 .BR XSH :
231 Specifications of functions (i.e., system calls and library
232 functions in actual implementations).
233 .IP
234 .BR XCU :
235 Specifications of commands and utilities
236 (i.e., the area formerly described by POSIX.2).
237 .IP
238 .BR XRAT :
239 Informative text on the other parts of the standard.
240 .IP
241 POSIX.1-2001 is aligned with C99, so that all of the
242 library functions standardized in C99 are also
243 standardized in POSIX.1-2001.
244 .IP
245 The Single UNIX Specification version 3 (SUSv3) comprises the
246 Base Specifications containing XBD, XSH, XCU, and XRAT as above,
247 plus X/Open Curses Issue 4 version 2 as an extra volume that is
248 not in POSIX.1-2001.
249 .IP
250 Two Technical Corrigenda (minor fixes and improvements)
251 of the original 2001 standard have occurred:
252 TC1 in 2003
253 and TC2 in 2004.
254 .TP
255 .B POSIX.1-2008, SUSv4
256 Work on the next revision of POSIX.1/SUS was completed and
257 ratified in 2008.
258 The standard is available online at
259 .UR http://www.unix.org\:/version4/
260 .UE .
261 .IP
262 The changes in this revision are not as large as those
263 that occurred for POSIX.1-2001/SUSv3,
264 but a number of new interfaces are added
265 and various details of existing specifications are modified.
266 Many of the interfaces that were optional in
267 POSIX.1-2001 become mandatory in the 2008 revision of the standard.
268 A few interfaces that are present in POSIX.1-2001 are marked
269 as obsolete in POSIX.1-2008, or removed from the standard altogether.
270 .IP
271 The revised standard is structured in the same way as its predecessor.
272 The Single UNIX Specification version 4 (SUSv4) comprises the
273 Base Specifications containing XBD, XSH, XCU, and XRAT,
274 plus X/Open Curses Issue 7 as an extra volume that is
275 not in POSIX.1-2008.
276 .IP
277 Again there are two levels of conformance: the baseline
278 .IR "POSIX Conformance" ,
279 and
280 .IR "XSI Conformance" ,
281 which mandates an additional set of interfaces
282 beyond those in the base specification.
283 .IP
284 In general, where the CONFORMING TO section of a manual page
285 lists POSIX.1-2001, it can be assumed that the interface also
286 conforms to POSIX.1-2008, unless otherwise noted.
287 .IP
288 Technical Corrigendum 1 (minor fixes and improvements)
289 of this standard was released in 2013.
290 .IP
291 Technical Corrigendum 2 of this standard was released in 2016.
292 .IP
293 Further information can be found on the Austin Group web site,
294 .UR http://www.opengroup.org\:/austin/
295 .UE .
296 .TP
297 .B SUSv4 2016 edition
298 This is equivalent to POSIX.1-2008, with the addition of
299 Technical Corrigenda 1 and 2 and the XCurses specification.
300 .TP
301 .B POSIX.1-2017
302 This revision of POSIX is technically identical to POSIX.1-2008 with
303 Technical Corrigenda 1 and 2 applied.
304 .TP
305 .B SUSv4 2018 edition
306 This is equivalent to POSIX.1-2017, with the addition of
307 the XCurses specification.
308 .PP
309 The interfaces documented in POSIX.1/SUS are available as
310 manual pages under sections 0p (header files), 1p (commands),
311 and 3p (functions);
312 thus one can write "man 3p open".
313 .SH SEE ALSO
314 .BR getconf (1),
315 .BR confstr (3),
316 .BR pathconf (3),
317 .BR sysconf (3),
318 .BR attributes (7),
319 .BR feature_test_macros (7),
320 .BR libc (7),
321 .BR posixoptions (7),
322 .BR system_data_types (7)