📛 NAME
standards - C and UNIX Standards
🚀 Quick Reference
| Use Case | Command | Description |
|---|
| Identify standard for a documented interface | man 7 standards | 📖 Lists all C and UNIX standards |
| Check POSIX conformance | man 3p function_name | ⚙️ View POSIX specification for a function |
| Understand standard acronyms | man 7 standards | 🔍 See descriptions of V7, 4.2BSD, System V, POSIX, SUS, etc. |
📖 DESCRIPTION
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 (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 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.
- 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 https://www.opengroup.org/platform/lfs.html.
- 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 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 1003.1c-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 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 http://www.unix.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.org/version3/. 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. The POSIX.1-2001 document is broken into four parts: XBD, XSH, XCU, XRAT. POSIX.1-2001 is aligned with C99. 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. Two Technical Corrigenda (TC1 in 2003 and TC2 in 2004) have occurred.
- 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 http://www.unix.org/version4/. Changes are not as large as for POSIX.1-2001/SUSv3, but many new interfaces added and some made mandatory. A few interfaces are marked obsolete. The revised standard is structured the same way. The Single UNIX Specification version 4 (SUSv4) comprises the Base Specifications plus X/Open Curses Issue 7. Two levels of conformance: POSIX Conformance and XSI Conformance. Technical Corrigendum 1 in 2013, Technical Corrigendum 2 in 2016. Further information at http://www.opengroup.org/austin/.
- 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 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
📜 COLOPHON
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