88 lines
4.1 KiB
HTML
88 lines
4.1 KiB
HTML
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<html>
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<meta name="Copyright" content="Copyright (c) 2006 by IBM Corporation">
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<title>HFS Concepts</title>
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<!-- All rights reserved. Licensed Materials Property of IBM -->
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<!--File Edited November 2001 -->
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<link rel="stylesheet" type="text/css" href="../rzahg/ic.css">
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</head>
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<body>
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</script>
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<h2>HFS Concepts</h2>
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<p>The HFS APIs work with units of information or objects that belong to
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existing, hierarchical file systems. A <strong>file system</strong> is the
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operating system's method of controlling the format of information on storage
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media and performing input and output operations to the objects that contain
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the information. The document library services (DLS) file system is one example
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of a file system.</p>
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<p>The basic units of nonrelational information in a file system are usually
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called <strong>files</strong>. Files are sometimes called <strong>byte-stream
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files</strong> or <strong>stream files</strong> because they consist of a
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stream of bytes with no specific record structure.</p>
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<p>A <strong>hierarchical file system</strong> arranges information units in a
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multilevel, tree-like structure, as IBM<SUP>(R)</SUP> DOS does. Files are grouped into larger
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units usually called directories. A <strong>directory</strong> can contain both
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files and subordinate directories. A directory contains no data of its own but
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is simply a named group of files and other directories. Two objects with the
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same name cannot exist in the same directory, but one directory can contain
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directories or files with the same names as those in another directory.</p>
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<p><strong><a name="HDRHDIRSC">HFS
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Directory--Scenario:</a></strong> The following diagram illustrates
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the structure of a hierarchical directory:</p>
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<center><img src="RBAFX506.gif" alt="Structure of a hierarchical directory">
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</center>
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<p>In the preceding diagram, the topmost directory, DIRA, contains both
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directories, DIRB and DIRD, and files, FILEW and FILEX. Directory DIRD contains
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only files. Directory DIRB contains only directories. In this structure, there
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are two directories named DIRD, one in directory DIRA and one in directory
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DIRA/DIRB. There are also three files named FILEX, one in directory DIRA, one
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in DIRA/DIRD, and one in DIRA/DIRB/DIRC.</p>
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<p>The specific location and name of a file or directory are represented in a
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multipart name called a path name. A <strong>path name</strong> starts with a
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slash (/) and consists of elements separated by slashes. The first element of
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the path name is the name of the file system. The remaining elements specify
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the applicable directory and file names; the last element can be either a file
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or a directory, but the rest must be directories.</p>
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<p><strong><a name="HDRHPATHEX">HFS Path
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Name--Example:</a></strong> The path name /QDLS/DIRA/FILEW refers
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to file FILEW in directory DIRA in file system QDLS.</p>
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<p><strong><a name="HDROPATHEX">Optical Path
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Name--Example:</a></strong> The path name /QOPT/VOL1/DIR1/FILEA
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refers to file FILEA in directory DIR1 on volume VOL1 in file system QOPT.</p>
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<p><strong>Note:</strong> The optical file system requires an optical volume
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name following the file system name in the path.</p>
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<hr>
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<center>
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<table cellpadding="2" cellspacing="2">
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<tr align="center">
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<td valign="middle" align="center"><a href="#Top_Of_Page">Top</a> | <a href=
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"hfs1.htm">Hierarchical File System APIs</a> | <a href="aplist.htm">APIs by
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category</a></td>
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</tr>
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</table>
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</center>
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</body>
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</html>
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