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diff --git a/posix-compliance/preface.rst b/posix-compliance/preface.rst new file mode 100644 index 0000000..48505d3 --- /dev/null +++ b/posix-compliance/preface.rst @@ -0,0 +1,33 @@ +.. comment SPDX-License-Identifier: CC-BY-SA-4.0 + +.. COMMENT: COPYRIGHT (c) 1988-2017. +.. COMMENT: On-Line Applications Research Corporation (OAR). +.. COMMENT: All rights reserved. + +Preface +======= + +RTEMS supports a variety of POSIX and BSD features including some POSIX +methods that are now deemed obsolete and some methods for compatibility +with GNU/Linux and FreeBSD. There are multiple POSIX standard versions +as well as multiple efforts to tailor (e.g. profile) POSIX for embedded +environments. They range in size from less than 200 required capabilities +to the full POSIX standard which has over 1200 required capabilities. This +document reports on the alignment of RTEMS with various standard versions +and defined profiles. + +RTEMS supports a number of POSIX process, user, and group oriented +routines in what is referred to as a "SUSP" (Single-User, Single +Process) manner. RTEMS supports a single process, multithreaded +POSIX environment. In a pure world, there would be no reason to even +include routines like ``getpid()`` when there can only be one process. +But providing routines like ``getpid()`` and making them work in +a sensible fashion for an embedded environment while not returning +``ENOSYS`` (for not implemented) makes it significantly easier to port +code from a UNIX environment without modifying it. + +Each chapter in this document presents the alignment of RTEMS with +a specific standard version or defined profile. Each section with a +chapter details the alignment of a specific header file relative to the +chapter's standard or profile. The implementation status of the items +required by the standard are listed. |