2.2 unix standardization

1． ISO c的标准。

ANSI C 1989 通过ISO认证，成为ISO/IEC标准

ANSI C 1999 通过ISO认证，成为…，增加了restrict关键字，在函数prototype声明时来限制pointer的使用。

C 的标准中不只用来定义C语言的语法和语义，他还包括了对standard C library的定义。

2. posix 标准

Posix 属于IEEE的标准，是一个标准集合，后来通过ISO认证，也成了ISO标准。称为posix.1。Posix初衷是为了制定一个unix个个版本之间portable operating system的interface，提高应用程序在各个unix版本之间的兼容性，后来这个标准被别的os也采用了。后来依次加入了real time扩展，pthreads的扩展，即multithread programming，event tracing，以及一些utilities。ISO C标准也被包括了进来。如下：

·         ISO/IEC 9945-1 (IEEE Standard 1003.1-1996), which includes

o        IEEE Standard 1003.1-1990

o        IEEE Standard 1003.1b-1993 (real-time extensions)

o        IEEE Standard 1003.1c-1995 (pthreads)

o        IEEE Standard 1003.1i-1995 (real-time technical corrigenda)

·         IEEE P1003.1a draft standard (system interface revision)

·         IEEE Standard 1003.1d-1999 (advanced real-time extensions)

·         IEEE Standard 1003.1j-2000 (more advanced real-time extensions)

·         IEEE Standard 1003.1q-2000 (tracing)

·         IEEE Standard 1003.2d-1994 (batch extensions)

·         IEEE P1003.2b draft standard (additional utilities)

·         Parts of IEEE Standard 1003.1g-2000 (protocol-independent interfaces)

·         ISO/IEC 9945-2 (IEEE Standard 1003.2-1993)

·         The Base Specifications of the Single UNIX Specification, version 2, which include

o        System Interface Definitions, Issue 5

o        Commands and Utilities, Issue 5

o        System Interfaces and Headers, Issue 5

·         Open Group Technical Standard, Networking Services, Issue 5.2

·         ISO/IEC 9899:1999, Programming Languages - C

Posix.1标准中并没有定义类似superuser的内容，但是某些function依赖于有一定权限的用户，而具体的定义要看具体的实现了。Posix.现在由Austin Group负责维护。

3．The Single Unix Specification (SUS)

The Single UNIX Specification, a superset of the POSIX.1 standard, specifies additional interfaces that extend the functionality provided by the basic POSIX.1 specification. The complete set of system interfaces is called the X/Open System Interface (XSI).

是posix.1的超集，简称XSI。

." Only XSI-conforming implementations can be called UNIX systems.

只有兼容XSI的系统才可以被称为是unix系统。

The Single UNIX Specification (SUS) is a publication of The Open Group, which was formed in 1996 as a merger of X/Open and the Open Software Foundation (OSF),

SUSv3的base definition和IEEE 1003.1-2001是一样的，可见SUS和Posix已经原来越接近。