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191 lines
7.7 KiB
HTML
191 lines
7.7 KiB
HTML
4 years ago
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<html>
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<!-- Copyright (C) 1988-2019 Free Software Foundation, Inc.
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.3 or
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any later version published by the Free Software Foundation; with the
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Invariant Sections being "Free Software" and "Free Software Needs
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Free Documentation", with the Front-Cover Texts being "A GNU Manual,"
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and with the Back-Cover Texts as in (a) below.
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(a) The FSF's Back-Cover Text is: "You are free to copy and modify
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this GNU Manual. Buying copies from GNU Press supports the FSF in
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developing GNU and promoting software freedom." -->
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<!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ -->
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<head>
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<title>Searching Memory (Debugging with GDB)</title>
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<meta name="description" content="Searching Memory (Debugging with GDB)">
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<meta name="keywords" content="Searching Memory (Debugging with GDB)">
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<meta name="resource-type" content="document">
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<meta name="distribution" content="global">
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<meta name="Generator" content="makeinfo">
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<link href="index.html#Top" rel="start" title="Top">
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<link href="Concept-Index.html#Concept-Index" rel="index" title="Concept Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="Data.html#Data" rel="up" title="Data">
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<link href="Value-Sizes.html#Value-Sizes" rel="next" title="Value Sizes">
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<link href="Caching-Target-Data.html#Caching-Target-Data" rel="prev" title="Caching Target Data">
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<style type="text/css">
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<!--
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a.summary-letter {text-decoration: none}
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blockquote.indentedblock {margin-right: 0em}
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blockquote.smallindentedblock {margin-right: 0em; font-size: smaller}
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blockquote.smallquotation {font-size: smaller}
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div.display {margin-left: 3.2em}
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div.example {margin-left: 3.2em}
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div.lisp {margin-left: 3.2em}
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div.smalldisplay {margin-left: 3.2em}
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div.smallexample {margin-left: 3.2em}
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div.smalllisp {margin-left: 3.2em}
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kbd {font-style: oblique}
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pre.display {font-family: inherit}
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pre.format {font-family: inherit}
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pre.menu-comment {font-family: serif}
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pre.menu-preformatted {font-family: serif}
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pre.smalldisplay {font-family: inherit; font-size: smaller}
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pre.smallexample {font-size: smaller}
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pre.smallformat {font-family: inherit; font-size: smaller}
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pre.smalllisp {font-size: smaller}
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span.nolinebreak {white-space: nowrap}
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span.roman {font-family: initial; font-weight: normal}
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span.sansserif {font-family: sans-serif; font-weight: normal}
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ul.no-bullet {list-style: none}
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-->
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</style>
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</head>
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<body lang="en">
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<a name="Searching-Memory"></a>
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<div class="header">
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<p>
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Next: <a href="Value-Sizes.html#Value-Sizes" accesskey="n" rel="next">Value Sizes</a>, Previous: <a href="Caching-Target-Data.html#Caching-Target-Data" accesskey="p" rel="prev">Caching Target Data</a>, Up: <a href="Data.html#Data" accesskey="u" rel="up">Data</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<a name="Search-Memory"></a>
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<h3 class="section">10.22 Search Memory</h3>
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<a name="index-searching-memory"></a>
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<p>Memory can be searched for a particular sequence of bytes with the
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<code>find</code> command.
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</p>
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<dl compact="compact">
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<dd><a name="index-find"></a>
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</dd>
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<dt><code>find <span class="roman">[</span>/<var>sn</var><span class="roman">]</span> <var>start_addr</var>, +<var>len</var>, <var>val1</var> <span class="roman">[</span>, <var>val2</var>, …<span class="roman">]</span></code></dt>
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<dt><code>find <span class="roman">[</span>/<var>sn</var><span class="roman">]</span> <var>start_addr</var>, <var>end_addr</var>, <var>val1</var> <span class="roman">[</span>, <var>val2</var>, …<span class="roman">]</span></code></dt>
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<dd><p>Search memory for the sequence of bytes specified by <var>val1</var>, <var>val2</var>,
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etc. The search begins at address <var>start_addr</var> and continues for either
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<var>len</var> bytes or through to <var>end_addr</var> inclusive.
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</p></dd>
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</dl>
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<p><var>s</var> and <var>n</var> are optional parameters.
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They may be specified in either order, apart or together.
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</p>
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<dl compact="compact">
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<dt><span class="roman"><var>s</var>, search query size</span></dt>
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<dd><p>The size of each search query value.
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</p>
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<dl compact="compact">
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<dt><code>b</code></dt>
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<dd><p>bytes
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</p></dd>
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<dt><code>h</code></dt>
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<dd><p>halfwords (two bytes)
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</p></dd>
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<dt><code>w</code></dt>
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<dd><p>words (four bytes)
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</p></dd>
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<dt><code>g</code></dt>
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<dd><p>giant words (eight bytes)
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</p></dd>
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</dl>
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<p>All values are interpreted in the current language.
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This means, for example, that if the current source language is C/C<tt>++</tt>
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then searching for the string “hello” includes the trailing ’\0’.
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The null terminator can be removed from searching by using casts,
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e.g.: ‘<samp>{char[5]}"hello"</samp>’.
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</p>
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<p>If the value size is not specified, it is taken from the
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value’s type in the current language.
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This is useful when one wants to specify the search
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pattern as a mixture of types.
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Note that this means, for example, that in the case of C-like languages
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a search for an untyped 0x42 will search for ‘<samp>(int) 0x42</samp>’
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which is typically four bytes.
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</p>
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</dd>
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<dt><span class="roman"><var>n</var>, maximum number of finds</span></dt>
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<dd><p>The maximum number of matches to print. The default is to print all finds.
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</p></dd>
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</dl>
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<p>You can use strings as search values. Quote them with double-quotes
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(<code>"</code>).
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The string value is copied into the search pattern byte by byte,
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regardless of the endianness of the target and the size specification.
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</p>
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<p>The address of each match found is printed as well as a count of the
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number of matches found.
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</p>
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<p>The address of the last value found is stored in convenience variable
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‘<samp>$_</samp>’.
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A count of the number of matches is stored in ‘<samp>$numfound</samp>’.
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</p>
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<p>For example, if stopped at the <code>printf</code> in this function:
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</p>
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<div class="smallexample">
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<pre class="smallexample">void
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hello ()
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{
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static char hello[] = "hello-hello";
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static struct { char c; short s; int i; }
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__attribute__ ((packed)) mixed
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= { 'c', 0x1234, 0x87654321 };
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printf ("%s\n", hello);
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}
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</pre></div>
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<p>you get during debugging:
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</p>
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<div class="smallexample">
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<pre class="smallexample">(gdb) find &hello[0], +sizeof(hello), "hello"
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0x804956d <hello.1620+6>
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1 pattern found
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(gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
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0x8049567 <hello.1620>
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0x804956d <hello.1620+6>
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2 patterns found.
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(gdb) find &hello[0], +sizeof(hello), {char[5]}"hello"
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0x8049567 <hello.1620>
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0x804956d <hello.1620+6>
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2 patterns found.
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(gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
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0x8049567 <hello.1620>
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1 pattern found
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(gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
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0x8049560 <mixed.1625>
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1 pattern found
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(gdb) print $numfound
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$1 = 1
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(gdb) print $_
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$2 = (void *) 0x8049560
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</pre></div>
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<hr>
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<div class="header">
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<p>
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Next: <a href="Value-Sizes.html#Value-Sizes" accesskey="n" rel="next">Value Sizes</a>, Previous: <a href="Caching-Target-Data.html#Caching-Target-Data" accesskey="p" rel="prev">Caching Target Data</a>, Up: <a href="Data.html#Data" accesskey="u" rel="up">Data</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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</body>
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</html>
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