source: rtems-docs/filesystem/preface.rst @ 14d532b

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Last change on this file since 14d532b was 14d532b, checked in by Amar Takhar <verm@…>, on 01/16/16 at 15:41:31

Fix section numbering, create TOC, seperate preface.

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1=======
2Preface
3=======
4
5This document describes the implementation of the RTEMS filesystem
6infrastructure.  This infrastructure supports the following
7capabilities:
8
9- Mountable file systems
10
11- Hierarchical file system directory structure
12
13- POSIX compliant set of routines for the manipulation of files and directories
14
15- Individual file and directory support for the following:
16  # Permissions for read, write and execute
17  # User ID
18  # Group ID
19  # Access time
20  # Modification time
21  # Creation time
22
23- Hard links to files and directories
24
25- Symbolic links to files and directories
26
27This has been implemented to provide the framework for a UNIX-like
28file system support. POSIX file and directory functions have been
29implemented that allow a standard method of accessing file, device and
30directory information within file systems. The file system concept that
31has been implemented allows for expansion and adaptation of the file
32system to a variety of existing and future data storage devices. To this
33end, file system mount and unmount capabilities have been included in this
34RTEMS framework.
35
36This framework slightly alters the manner in which devices are handled
37under RTEMS from that of public release 4.0.0 and earlier.  Devices that
38are defined under a given RTEMS configuration will now be registered as
39files in a mounted file system.  Access to these device drivers and their
40associated devices may now be performed through the traditional file system
41open(), read(), write(), lseek(), fstat() and ioctl() functions in addition
42to the interface provided by the IO Manager in the RTEMS Classic API.
43
44An In-Memory File System (IMFS) is included which provides full POSIX
45filesystem functionality yet is RAM based.  The IMFS maintains a
46node structure for each file, device, and directory in each mounted
47instantiation of its file system. The node structure is used to
48manage ownership, access rights, access time, modification time,
49and creation time.  A union of structures within the IMFS nodal
50structure provide for manipulation of file data, device selection,
51or directory content as required by the nodal type. Manipulation of
52these properties is accomplished through the POSIX set of file and
53directory functions.  In addition to being useful in its own right,
54the IMFS serves as a full featured example filesystem.
55
56The intended audience for this document is those persons implementing
57their own filesystem.  Users of the filesystem may find information
58on the implementation useful.  But the user interface to the filesystem
59is through the ISO/ANSI C Library and POSIX 1003.1b file and directory
60APIs.
61
62.. COMMENT: COPYRIGHT (c) 1988-2002.
63
64.. COMMENT: On-Line Applications Research Corporation (OAR).
65
66.. COMMENT: All rights reserved.
67
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