UnixStandards < Training2

%SECTION0{name=UnixStandards}% Standards and Portability in the Unix world

_"The nice thing about standards is that there are so many of them to choose from."_ A. S. Tanenbaum

*C*
   * ANSI C (1989)
   * currently: C99 (1999)

*portability of other languages:*
   * perl, python, c++, shell scripts

*Unix*
   * early diversity of early Unices provoked standardization at early as 1983 (UDS83)
   * POSIX (name suggested by R. Stallman), first release 1990

relevant today:

   * SUS (Single Unix Specification)
      * SUS conformance test required to use "UNIX" name
      * specifies the POSIX base (1003.1)
      * in contrast to POSIX freely available

   * POSIX (by IEEE) defines
      * 1003.1: C API
      * 1003.2: Shells and helper programs (ksh, vi, awk, sed)
      * 1003.1b: realtime extensions
      * 1003.1c: threads
      * -> is the basis of all later standards 

    * FHS (Filesystem Hierarchy Standard)
      * above standards specify "what"
      * FHS specifies "where"

   * Linux Standard Base
      * Meta-Standard
      * incorporates the above specifications and extends

   * IETF RFCs
      * working implementation required!

   * best way to achieve portability is use of Free Software
4.2.1. Licensing Models		1. Denx Training Topics		4.2.3. Working with Free Software
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