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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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+<head>
+<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
+<!-- This document describes the GNU History library
+(version 8.2, 19 September 2022),
+a programming tool that provides a consistent user interface for
+recalling lines of previously typed input.
+
+Copyright (C) 1988-2022 Free Software Foundation, Inc.
+
+Permission is granted to copy, distribute and/or modify this document
+under the terms of the GNU Free Documentation License, Version 1.3 or
+any later version published by the Free Software Foundation; with no
+Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.
+A copy of the license is included in the section entitled
+"GNU Free Documentation License".
+ -->
+<title>GNU History Library</title>
+
+<meta name="description" content="GNU History Library">
+<meta name="keywords" content="GNU History Library">
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+
+<link href="#Top" rel="start" title="Top">
+<link href="#Concept-Index" rel="index" title="Concept Index">
+<link href="#SEC_Contents" rel="contents" title="Table of Contents">
+<link href="#Using-History-Interactively" rel="next" title="Using History Interactively">
+<style type="text/css">
+<!--
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+</head>
+
+<body lang="en">
+<h1 class="settitle" align="center">GNU History Library</h1>
+
+
+
+
+
+
+
+
+
+<div class="top" id="Top">
+<div class="header">
+<p>
+Next: <a href="#Using-History-Interactively" accesskey="n" rel="next">Using History Interactively</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Concept-Index" title="Index" rel="index">Index</a>]</p>
+</div>
+<span id="GNU-History-Library"></span><h1 class="top">GNU History Library</h1>
+
+<p>This document describes the GNU History library, a programming tool that
+provides a consistent user interface for recalling lines of previously
+typed input.
+</p>
+
+
+
+<div class="Contents_element" id="SEC_Contents">
+<h2 class="contents-heading">Table of Contents</h2>
+
+<div class="contents">
+
+<ul class="no-bullet">
+ <li><a id="toc-Using-History-Interactively-1" href="#Using-History-Interactively">1 Using History Interactively</a>
+ <ul class="no-bullet">
+ <li><a id="toc-History-Expansion-1" href="#History-Interaction">1.1 History Expansion</a>
+ <ul class="no-bullet">
+ <li><a id="toc-Event-Designators-1" href="#Event-Designators">1.1.1 Event Designators</a></li>
+ <li><a id="toc-Word-Designators-1" href="#Word-Designators">1.1.2 Word Designators</a></li>
+ <li><a id="toc-Modifiers-1" href="#Modifiers">1.1.3 Modifiers</a></li>
+ </ul></li>
+ </ul></li>
+ <li><a id="toc-Programming-with-GNU-History-1" href="#Programming-with-GNU-History">2 Programming with GNU History</a>
+ <ul class="no-bullet">
+ <li><a id="toc-Introduction-to-History-1" href="#Introduction-to-History">2.1 Introduction to History</a></li>
+ <li><a id="toc-History-Storage-1" href="#History-Storage">2.2 History Storage</a></li>
+ <li><a id="toc-History-Functions-1" href="#History-Functions">2.3 History Functions</a>
+ <ul class="no-bullet">
+ <li><a id="toc-Initializing-History-and-State-Management-1" href="#Initializing-History-and-State-Management">2.3.1 Initializing History and State Management</a></li>
+ <li><a id="toc-History-List-Management-1" href="#History-List-Management">2.3.2 History List Management</a></li>
+ <li><a id="toc-Information-About-the-History-List-1" href="#Information-About-the-History-List">2.3.3 Information About the History List</a></li>
+ <li><a id="toc-Moving-Around-the-History-List-1" href="#Moving-Around-the-History-List">2.3.4 Moving Around the History List</a></li>
+ <li><a id="toc-Searching-the-History-List-1" href="#Searching-the-History-List">2.3.5 Searching the History List</a></li>
+ <li><a id="toc-Managing-the-History-File-1" href="#Managing-the-History-File">2.3.6 Managing the History File</a></li>
+ <li><a id="toc-History-Expansion-2" href="#History-Expansion">2.3.7 History Expansion</a></li>
+ </ul></li>
+ <li><a id="toc-History-Variables-1" href="#History-Variables">2.4 History Variables</a></li>
+ <li><a id="toc-History-Programming-Example-1" href="#History-Programming-Example">2.5 History Programming Example</a></li>
+ </ul></li>
+ <li><a id="toc-GNU-Free-Documentation-License-1" href="#GNU-Free-Documentation-License">Appendix A GNU Free Documentation License</a></li>
+ <li><a id="toc-Concept-Index-1" href="#Concept-Index" rel="index">Appendix B Concept Index</a></li>
+ <li><a id="toc-Function-and-Variable-Index-1" href="#Function-and-Variable-Index" rel="index">Appendix C Function and Variable Index</a></li>
+</ul>
+</div>
+</div>
+<hr>
+<div class="chapter" id="Using-History-Interactively">
+<div class="header">
+<p>
+Next: <a href="#Programming-with-GNU-History" accesskey="n" rel="next">Programming with GNU History</a>, Previous: <a href="#Top" accesskey="p" rel="prev">GNU History Library</a>, Up: <a href="#Top" accesskey="u" rel="up">GNU History Library</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Concept-Index" title="Index" rel="index">Index</a>]</p>
+</div>
+<span id="Using-History-Interactively-1"></span><h2 class="chapter">1 Using History Interactively</h2>
+
+
+<p>This chapter describes how to use the <small>GNU</small> History Library interactively,
+from a user&rsquo;s standpoint. It should be considered a user&rsquo;s guide. For
+information on using the <small>GNU</small> History Library in your own programs,
+see <a href="#Programming-with-GNU-History">Programming with GNU History</a>.
+</p>
+
+
+<ul class="section-toc">
+<li><a href="#History-Interaction" accesskey="1">History Expansion</a></li>
+</ul>
+<hr>
+<div class="section" id="History-Interaction">
+<div class="header">
+<p>
+Up: <a href="#Using-History-Interactively" accesskey="u" rel="up">Using History Interactively</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Concept-Index" title="Index" rel="index">Index</a>]</p>
+</div>
+<span id="History-Expansion-1"></span><h3 class="section">1.1 History Expansion</h3>
+<span id="index-history-expansion"></span>
+
+<p>The History library provides a history expansion feature that is similar
+to the history expansion provided by <code>csh</code>. This section
+describes the syntax used to manipulate the history information.
+</p>
+<p>History expansions introduce words from the history list into
+the input stream, making it easy to repeat commands, insert the
+arguments to a previous command into the current input line, or
+fix errors in previous commands quickly.
+</p>
+
+<p>History expansion takes place in two parts. The first is to determine
+which line from the history list should be used during substitution.
+The second is to select portions of that line for inclusion into the
+current one. The line selected from the history is called the
+<em>event</em>, and the portions of that line that are acted upon are
+called <em>words</em>. Various <em>modifiers</em> are available to manipulate
+the selected words. The line is broken into words in the same fashion
+that Bash does, so that several words
+surrounded by quotes are considered one word.
+History expansions are introduced by the appearance of the
+history expansion character, which is &lsquo;<samp>!</samp>&rsquo; by default.
+</p>
+<p>History expansion implements shell-like quoting conventions:
+a backslash can be used to remove the special handling for the next character;
+single quotes enclose verbatim sequences of characters, and can be used to
+inhibit history expansion;
+and characters enclosed within double quotes may be subject to history
+expansion, since backslash can escape the history expansion character,
+but single quotes may not, since they are not treated specially within
+double quotes.
+</p>
+
+
+
+<ul class="section-toc">
+<li><a href="#Event-Designators" accesskey="1">Event Designators</a></li>
+<li><a href="#Word-Designators" accesskey="2">Word Designators</a></li>
+<li><a href="#Modifiers" accesskey="3">Modifiers</a></li>
+</ul>
+<hr>
+<div class="subsection" id="Event-Designators">
+<div class="header">
+<p>
+Next: <a href="#Word-Designators" accesskey="n" rel="next">Word Designators</a>, Up: <a href="#History-Interaction" accesskey="u" rel="up">History Expansion</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Concept-Index" title="Index" rel="index">Index</a>]</p>
+</div>
+<span id="Event-Designators-1"></span><h4 class="subsection">1.1.1 Event Designators</h4>
+<span id="index-event-designators"></span>
+
+<p>An event designator is a reference to a command line entry in the
+history list.
+Unless the reference is absolute, events are relative to the current
+position in the history list.
+<span id="index-history-events"></span>
+</p>
+<dl compact="compact">
+<dt><span><code>!</code></span></dt>
+<dd><p>Start a history substitution, except when followed by a space, tab,
+the end of the line, or &lsquo;<samp>=</samp>&rsquo;.
+</p>
+</dd>
+<dt><span><code>!<var>n</var></code></span></dt>
+<dd><p>Refer to command line <var>n</var>.
+</p>
+</dd>
+<dt><span><code>!-<var>n</var></code></span></dt>
+<dd><p>Refer to the command <var>n</var> lines back.
+</p>
+</dd>
+<dt><span><code>!!</code></span></dt>
+<dd><p>Refer to the previous command. This is a synonym for &lsquo;<samp>!-1</samp>&rsquo;.
+</p>
+</dd>
+<dt><span><code>!<var>string</var></code></span></dt>
+<dd><p>Refer to the most recent command
+preceding the current position in the history list
+starting with <var>string</var>.
+</p>
+</dd>
+<dt><span><code>!?<var>string</var>[?]</code></span></dt>
+<dd><p>Refer to the most recent command
+preceding the current position in the history list
+containing <var>string</var>.
+The trailing
+&lsquo;<samp>?</samp>&rsquo; may be omitted if the <var>string</var> is followed immediately by
+a newline.
+If <var>string</var> is missing, the string from the most recent search is used;
+it is an error if there is no previous search string.
+</p>
+</dd>
+<dt><span><code>^<var>string1</var>^<var>string2</var>^</code></span></dt>
+<dd><p>Quick Substitution. Repeat the last command, replacing <var>string1</var>
+with <var>string2</var>. Equivalent to
+<code>!!:s^<var>string1</var>^<var>string2</var>^</code>.
+</p>
+</dd>
+<dt><span><code>!#</code></span></dt>
+<dd><p>The entire command line typed so far.
+</p>
+</dd>
+</dl>
+
+<hr>
+</div>
+<div class="subsection" id="Word-Designators">
+<div class="header">
+<p>
+Next: <a href="#Modifiers" accesskey="n" rel="next">Modifiers</a>, Previous: <a href="#Event-Designators" accesskey="p" rel="prev">Event Designators</a>, Up: <a href="#History-Interaction" accesskey="u" rel="up">History Expansion</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Concept-Index" title="Index" rel="index">Index</a>]</p>
+</div>
+<span id="Word-Designators-1"></span><h4 class="subsection">1.1.2 Word Designators</h4>
+
+<p>Word designators are used to select desired words from the event.
+A &lsquo;<samp>:</samp>&rsquo; separates the event specification from the word designator. It
+may be omitted if the word designator begins with a &lsquo;<samp>^</samp>&rsquo;, &lsquo;<samp>$</samp>&rsquo;,
+&lsquo;<samp>*</samp>&rsquo;, &lsquo;<samp>-</samp>&rsquo;, or &lsquo;<samp>%</samp>&rsquo;. Words are numbered from the beginning
+of the line, with the first word being denoted by 0 (zero). Words are
+inserted into the current line separated by single spaces.
+</p>
+<p>For example,
+</p>
+<dl compact="compact">
+<dt><span><code>!!</code></span></dt>
+<dd><p>designates the preceding command. When you type this, the preceding
+command is repeated in toto.
+</p>
+</dd>
+<dt><span><code>!!:$</code></span></dt>
+<dd><p>designates the last argument of the preceding command. This may be
+shortened to <code>!$</code>.
+</p>
+</dd>
+<dt><span><code>!fi:2</code></span></dt>
+<dd><p>designates the second argument of the most recent command starting with
+the letters <code>fi</code>.
+</p></dd>
+</dl>
+
+<p>Here are the word designators:
+</p>
+<dl compact="compact">
+<dt><span><code>0 (zero)</code></span></dt>
+<dd><p>The <code>0</code>th word. For many applications, this is the command word.
+</p>
+</dd>
+<dt><span><code><var>n</var></code></span></dt>
+<dd><p>The <var>n</var>th word.
+</p>
+</dd>
+<dt><span><code>^</code></span></dt>
+<dd><p>The first argument; that is, word 1.
+</p>
+</dd>
+<dt><span><code>$</code></span></dt>
+<dd><p>The last argument.
+</p>
+</dd>
+<dt><span><code>%</code></span></dt>
+<dd><p>The first word matched by the most recent &lsquo;<samp>?<var>string</var>?</samp>&rsquo; search,
+if the search string begins with a character that is part of a word.
+</p>
+</dd>
+<dt><span><code><var>x</var>-<var>y</var></code></span></dt>
+<dd><p>A range of words; &lsquo;<samp>-<var>y</var></samp>&rsquo; abbreviates &lsquo;<samp>0-<var>y</var></samp>&rsquo;.
+</p>
+</dd>
+<dt><span><code>*</code></span></dt>
+<dd><p>All of the words, except the <code>0</code>th. This is a synonym for &lsquo;<samp>1-$</samp>&rsquo;.
+It is not an error to use &lsquo;<samp>*</samp>&rsquo; if there is just one word in the event;
+the empty string is returned in that case.
+</p>
+</dd>
+<dt><span><code><var>x</var>*</code></span></dt>
+<dd><p>Abbreviates &lsquo;<samp><var>x</var>-$</samp>&rsquo;
+</p>
+</dd>
+<dt><span><code><var>x</var>-</code></span></dt>
+<dd><p>Abbreviates &lsquo;<samp><var>x</var>-$</samp>&rsquo; like &lsquo;<samp><var>x</var>*</samp>&rsquo;, but omits the last word.
+If &lsquo;<samp>x</samp>&rsquo; is missing, it defaults to 0.
+</p>
+</dd>
+</dl>
+
+<p>If a word designator is supplied without an event specification, the
+previous command is used as the event.
+</p>
+<hr>
+</div>
+<div class="subsection" id="Modifiers">
+<div class="header">
+<p>
+Previous: <a href="#Word-Designators" accesskey="p" rel="prev">Word Designators</a>, Up: <a href="#History-Interaction" accesskey="u" rel="up">History Expansion</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Concept-Index" title="Index" rel="index">Index</a>]</p>
+</div>
+<span id="Modifiers-1"></span><h4 class="subsection">1.1.3 Modifiers</h4>
+
+<p>After the optional word designator, you can add a sequence of one or more
+of the following modifiers, each preceded by a &lsquo;<samp>:</samp>&rsquo;.
+These modify, or edit, the word or words selected from the history event.
+</p>
+<dl compact="compact">
+<dt><span><code>h</code></span></dt>
+<dd><p>Remove a trailing pathname component, leaving only the head.
+</p>
+</dd>
+<dt><span><code>t</code></span></dt>
+<dd><p>Remove all leading pathname components, leaving the tail.
+</p>
+</dd>
+<dt><span><code>r</code></span></dt>
+<dd><p>Remove a trailing suffix of the form &lsquo;<samp>.<var>suffix</var></samp>&rsquo;, leaving
+the basename.
+</p>
+</dd>
+<dt><span><code>e</code></span></dt>
+<dd><p>Remove all but the trailing suffix.
+</p>
+</dd>
+<dt><span><code>p</code></span></dt>
+<dd><p>Print the new command but do not execute it.
+</p>
+
+</dd>
+<dt><span><code>s/<var>old</var>/<var>new</var>/</code></span></dt>
+<dd><p>Substitute <var>new</var> for the first occurrence of <var>old</var> in the
+event line.
+Any character may be used as the delimiter in place of &lsquo;<samp>/</samp>&rsquo;.
+The delimiter may be quoted in <var>old</var> and <var>new</var>
+with a single backslash. If &lsquo;<samp>&amp;</samp>&rsquo; appears in <var>new</var>,
+it is replaced by <var>old</var>. A single backslash will quote
+the &lsquo;<samp>&amp;</samp>&rsquo;.
+If <var>old</var> is null, it is set to the last <var>old</var>
+substituted, or, if no previous history substitutions took place,
+the last <var>string</var>
+in a !?<var>string</var><code>[?]</code>
+search.
+If <var>new</var> is null, each matching <var>old</var> is deleted.
+The final delimiter is optional if it is the last
+character on the input line.
+</p>
+</dd>
+<dt><span><code>&amp;</code></span></dt>
+<dd><p>Repeat the previous substitution.
+</p>
+</dd>
+<dt><span><code>g</code></span></dt>
+<dt><span><code>a</code></span></dt>
+<dd><p>Cause changes to be applied over the entire event line. Used in
+conjunction with &lsquo;<samp>s</samp>&rsquo;, as in <code>gs/<var>old</var>/<var>new</var>/</code>,
+or with &lsquo;<samp>&amp;</samp>&rsquo;.
+</p>
+</dd>
+<dt><span><code>G</code></span></dt>
+<dd><p>Apply the following &lsquo;<samp>s</samp>&rsquo; or &lsquo;<samp>&amp;</samp>&rsquo; modifier once to each word
+in the event.
+</p>
+</dd>
+</dl>
+
+<hr>
+</div>
+</div>
+</div>
+<div class="chapter" id="Programming-with-GNU-History">
+<div class="header">
+<p>
+Next: <a href="#GNU-Free-Documentation-License" accesskey="n" rel="next">GNU Free Documentation License</a>, Previous: <a href="#Using-History-Interactively" accesskey="p" rel="prev">Using History Interactively</a>, Up: <a href="#Top" accesskey="u" rel="up">GNU History Library</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Concept-Index" title="Index" rel="index">Index</a>]</p>
+</div>
+<span id="Programming-with-GNU-History-1"></span><h2 class="chapter">2 Programming with GNU History</h2>
+
+<p>This chapter describes how to interface programs that you write
+with the <small>GNU</small> History Library.
+It should be considered a technical guide.
+For information on the interactive use of <small>GNU</small> History, see <a href="#Using-History-Interactively">Using History Interactively</a>.
+</p>
+
+<ul class="section-toc">
+<li><a href="#Introduction-to-History" accesskey="1">Introduction to History</a></li>
+<li><a href="#History-Storage" accesskey="2">History Storage</a></li>
+<li><a href="#History-Functions" accesskey="3">History Functions</a></li>
+<li><a href="#History-Variables" accesskey="4">History Variables</a></li>
+<li><a href="#History-Programming-Example" accesskey="5">History Programming Example</a></li>
+</ul>
+<hr>
+<div class="section" id="Introduction-to-History">
+<div class="header">
+<p>
+Next: <a href="#History-Storage" accesskey="n" rel="next">History Storage</a>, Up: <a href="#Programming-with-GNU-History" accesskey="u" rel="up">Programming with GNU History</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Concept-Index" title="Index" rel="index">Index</a>]</p>
+</div>
+<span id="Introduction-to-History-1"></span><h3 class="section">2.1 Introduction to History</h3>
+
+<p>Many programs read input from the user a line at a time. The <small>GNU</small>
+History library is able to keep track of those lines, associate arbitrary
+data with each line, and utilize information from previous lines in
+composing new ones.
+</p>
+<p>A programmer using the History library has available functions
+for remembering lines on a history list, associating arbitrary data
+with a line, removing lines from the list, searching through the list
+for a line containing an arbitrary text string, and referencing any line
+in the list directly. In addition, a history <em>expansion</em> function
+is available which provides for a consistent user interface across
+different programs.
+</p>
+<p>The user using programs written with the History library has the
+benefit of a consistent user interface with a set of well-known
+commands for manipulating the text of previous lines and using that text
+in new commands. The basic history manipulation commands are similar to
+the history substitution provided by <code>csh</code>.
+</p>
+<p>The programmer can also use the Readline library, which
+includes some history manipulation by default, and has the added
+advantage of command line editing.
+</p>
+<p>Before declaring any functions using any functionality the History
+library provides in other code, an application writer should include
+the file <code>&lt;readline/history.h&gt;</code> in any file that uses the
+History library&rsquo;s features. It supplies extern declarations for all
+of the library&rsquo;s public functions and variables, and declares all of
+the public data structures.
+</p>
+<hr>
+</div>
+<div class="section" id="History-Storage">
+<div class="header">
+<p>
+Next: <a href="#History-Functions" accesskey="n" rel="next">History Functions</a>, Previous: <a href="#Introduction-to-History" accesskey="p" rel="prev">Introduction to History</a>, Up: <a href="#Programming-with-GNU-History" accesskey="u" rel="up">Programming with GNU History</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Concept-Index" title="Index" rel="index">Index</a>]</p>
+</div>
+<span id="History-Storage-1"></span><h3 class="section">2.2 History Storage</h3>
+
+<p>The history list is an array of history entries. A history entry is
+declared as follows:
+</p>
+<div class="example">
+<pre class="example">typedef void *histdata_t;
+
+typedef struct _hist_entry {
+ char *line;
+ char *timestamp;
+ histdata_t data;
+} HIST_ENTRY;
+</pre></div>
+
+<p>The history list itself might therefore be declared as
+</p>
+<div class="example">
+<pre class="example">HIST_ENTRY **the_history_list;
+</pre></div>
+
+<p>The state of the History library is encapsulated into a single structure:
+</p>
+<div class="example">
+<pre class="example">/*
+ * A structure used to pass around the current state of the history.
+ */
+typedef struct _hist_state {
+ HIST_ENTRY **entries; /* Pointer to the entries themselves. */
+ int offset; /* The location pointer within this array. */
+ int length; /* Number of elements within this array. */
+ int size; /* Number of slots allocated to this array. */
+ int flags;
+} HISTORY_STATE;
+</pre></div>
+
+<p>If the flags member includes <code>HS_STIFLED</code>, the history has been
+stifled.
+</p>
+<hr>
+</div>
+<div class="section" id="History-Functions">
+<div class="header">
+<p>
+Next: <a href="#History-Variables" accesskey="n" rel="next">History Variables</a>, Previous: <a href="#History-Storage" accesskey="p" rel="prev">History Storage</a>, Up: <a href="#Programming-with-GNU-History" accesskey="u" rel="up">Programming with GNU History</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Concept-Index" title="Index" rel="index">Index</a>]</p>
+</div>
+<span id="History-Functions-1"></span><h3 class="section">2.3 History Functions</h3>
+
+<p>This section describes the calling sequence for the various functions
+exported by the <small>GNU</small> History library.
+</p>
+
+<ul class="section-toc">
+<li><a href="#Initializing-History-and-State-Management" accesskey="1">Initializing History and State Management</a></li>
+<li><a href="#History-List-Management" accesskey="2">History List Management</a></li>
+<li><a href="#Information-About-the-History-List" accesskey="3">Information About the History List</a></li>
+<li><a href="#Moving-Around-the-History-List" accesskey="4">Moving Around the History List</a></li>
+<li><a href="#Searching-the-History-List" accesskey="5">Searching the History List</a></li>
+<li><a href="#Managing-the-History-File" accesskey="6">Managing the History File</a></li>
+<li><a href="#History-Expansion" accesskey="7">History Expansion</a></li>
+</ul>
+<hr>
+<div class="subsection" id="Initializing-History-and-State-Management">
+<div class="header">
+<p>
+Next: <a href="#History-List-Management" accesskey="n" rel="next">History List Management</a>, Up: <a href="#History-Functions" accesskey="u" rel="up">History Functions</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Concept-Index" title="Index" rel="index">Index</a>]</p>
+</div>
+<span id="Initializing-History-and-State-Management-1"></span><h4 class="subsection">2.3.1 Initializing History and State Management</h4>
+
+<p>This section describes functions used to initialize and manage
+the state of the History library when you want to use the history
+functions in your program.
+</p>
+<dl class="def">
+<dt id="index-using_005fhistory"><span class="category">Function: </span><span><em>void</em> <strong>using_history</strong> <em>(void)</em><a href='#index-using_005fhistory' class='copiable-anchor'> &para;</a></span></dt>
+<dd><p>Begin a session in which the history functions might be used. This
+initializes the interactive variables.
+</p></dd></dl>
+
+<dl class="def">
+<dt id="index-history_005fget_005fhistory_005fstate"><span class="category">Function: </span><span><em>HISTORY_STATE *</em> <strong>history_get_history_state</strong> <em>(void)</em><a href='#index-history_005fget_005fhistory_005fstate' class='copiable-anchor'> &para;</a></span></dt>
+<dd><p>Return a structure describing the current state of the input history.
+</p></dd></dl>
+
+<dl class="def">
+<dt id="index-history_005fset_005fhistory_005fstate"><span class="category">Function: </span><span><em>void</em> <strong>history_set_history_state</strong> <em>(HISTORY_STATE *state)</em><a href='#index-history_005fset_005fhistory_005fstate' class='copiable-anchor'> &para;</a></span></dt>
+<dd><p>Set the state of the history list according to <var>state</var>.
+</p></dd></dl>
+
+<hr>
+</div>
+<div class="subsection" id="History-List-Management">
+<div class="header">
+<p>
+Next: <a href="#Information-About-the-History-List" accesskey="n" rel="next">Information About the History List</a>, Previous: <a href="#Initializing-History-and-State-Management" accesskey="p" rel="prev">Initializing History and State Management</a>, Up: <a href="#History-Functions" accesskey="u" rel="up">History Functions</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Concept-Index" title="Index" rel="index">Index</a>]</p>
+</div>
+<span id="History-List-Management-1"></span><h4 class="subsection">2.3.2 History List Management</h4>
+
+<p>These functions manage individual entries on the history list, or set
+parameters managing the list itself.
+</p>
+<dl class="def">
+<dt id="index-add_005fhistory"><span class="category">Function: </span><span><em>void</em> <strong>add_history</strong> <em>(const char *string)</em><a href='#index-add_005fhistory' class='copiable-anchor'> &para;</a></span></dt>
+<dd><p>Place <var>string</var> at the end of the history list. The associated data
+field (if any) is set to <code>NULL</code>.
+If the maximum number of history entries has been set using
+<code>stifle_history()</code>, and the new number of history entries would exceed
+that maximum, the oldest history entry is removed.
+</p></dd></dl>
+
+<dl class="def">
+<dt id="index-add_005fhistory_005ftime"><span class="category">Function: </span><span><em>void</em> <strong>add_history_time</strong> <em>(const char *string)</em><a href='#index-add_005fhistory_005ftime' class='copiable-anchor'> &para;</a></span></dt>
+<dd><p>Change the time stamp associated with the most recent history entry to
+<var>string</var>.
+</p></dd></dl>
+
+<dl class="def">
+<dt id="index-remove_005fhistory"><span class="category">Function: </span><span><em>HIST_ENTRY *</em> <strong>remove_history</strong> <em>(int which)</em><a href='#index-remove_005fhistory' class='copiable-anchor'> &para;</a></span></dt>
+<dd><p>Remove history entry at offset <var>which</var> from the history. The
+removed element is returned so you can free the line, data,
+and containing structure.
+</p></dd></dl>
+
+<dl class="def">
+<dt id="index-free_005fhistory_005fentry"><span class="category">Function: </span><span><em>histdata_t</em> <strong>free_history_entry</strong> <em>(HIST_ENTRY *histent)</em><a href='#index-free_005fhistory_005fentry' class='copiable-anchor'> &para;</a></span></dt>
+<dd><p>Free the history entry <var>histent</var> and any history library private
+data associated with it. Returns the application-specific data
+so the caller can dispose of it.
+</p></dd></dl>
+
+<dl class="def">
+<dt id="index-replace_005fhistory_005fentry"><span class="category">Function: </span><span><em>HIST_ENTRY *</em> <strong>replace_history_entry</strong> <em>(int which, const char *line, histdata_t data)</em><a href='#index-replace_005fhistory_005fentry' class='copiable-anchor'> &para;</a></span></dt>
+<dd><p>Make the history entry at offset <var>which</var> have <var>line</var> and <var>data</var>.
+This returns the old entry so the caller can dispose of any
+application-specific data. In the case
+of an invalid <var>which</var>, a <code>NULL</code> pointer is returned.
+</p></dd></dl>
+
+<dl class="def">
+<dt id="index-clear_005fhistory"><span class="category">Function: </span><span><em>void</em> <strong>clear_history</strong> <em>(void)</em><a href='#index-clear_005fhistory' class='copiable-anchor'> &para;</a></span></dt>
+<dd><p>Clear the history list by deleting all the entries.
+</p></dd></dl>
+
+<dl class="def">
+<dt id="index-stifle_005fhistory"><span class="category">Function: </span><span><em>void</em> <strong>stifle_history</strong> <em>(int max)</em><a href='#index-stifle_005fhistory' class='copiable-anchor'> &para;</a></span></dt>
+<dd><p>Stifle the history list, remembering only the last <var>max</var> entries.
+The history list will contain only <var>max</var> entries at a time.
+</p></dd></dl>
+
+<dl class="def">
+<dt id="index-unstifle_005fhistory"><span class="category">Function: </span><span><em>int</em> <strong>unstifle_history</strong> <em>(void)</em><a href='#index-unstifle_005fhistory' class='copiable-anchor'> &para;</a></span></dt>
+<dd><p>Stop stifling the history. This returns the previously-set
+maximum number of history entries (as set by <code>stifle_history()</code>).
+The value is positive if the history was
+stifled, negative if it wasn&rsquo;t.
+</p></dd></dl>
+
+<dl class="def">
+<dt id="index-history_005fis_005fstifled"><span class="category">Function: </span><span><em>int</em> <strong>history_is_stifled</strong> <em>(void)</em><a href='#index-history_005fis_005fstifled' class='copiable-anchor'> &para;</a></span></dt>
+<dd><p>Returns non-zero if the history is stifled, zero if it is not.
+</p></dd></dl>
+
+<hr>
+</div>
+<div class="subsection" id="Information-About-the-History-List">
+<div class="header">
+<p>
+Next: <a href="#Moving-Around-the-History-List" accesskey="n" rel="next">Moving Around the History List</a>, Previous: <a href="#History-List-Management" accesskey="p" rel="prev">History List Management</a>, Up: <a href="#History-Functions" accesskey="u" rel="up">History Functions</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Concept-Index" title="Index" rel="index">Index</a>]</p>
+</div>
+<span id="Information-About-the-History-List-1"></span><h4 class="subsection">2.3.3 Information About the History List</h4>
+
+<p>These functions return information about the entire history list or
+individual list entries.
+</p>
+<dl class="def">
+<dt id="index-history_005flist"><span class="category">Function: </span><span><em>HIST_ENTRY **</em> <strong>history_list</strong> <em>(void)</em><a href='#index-history_005flist' class='copiable-anchor'> &para;</a></span></dt>
+<dd><p>Return a <code>NULL</code> terminated array of <code>HIST_ENTRY *</code> which is the
+current input history. Element 0 of this list is the beginning of time.
+If there is no history, return <code>NULL</code>.
+</p></dd></dl>
+
+<dl class="def">
+<dt id="index-where_005fhistory"><span class="category">Function: </span><span><em>int</em> <strong>where_history</strong> <em>(void)</em><a href='#index-where_005fhistory' class='copiable-anchor'> &para;</a></span></dt>
+<dd><p>Returns the offset of the current history element.
+</p></dd></dl>
+
+<dl class="def">
+<dt id="index-current_005fhistory"><span class="category">Function: </span><span><em>HIST_ENTRY *</em> <strong>current_history</strong> <em>(void)</em><a href='#index-current_005fhistory' class='copiable-anchor'> &para;</a></span></dt>
+<dd><p>Return the history entry at the current position, as determined by
+<code>where_history()</code>. If there is no entry there, return a <code>NULL</code>
+pointer.
+</p></dd></dl>
+
+<dl class="def">
+<dt id="index-history_005fget"><span class="category">Function: </span><span><em>HIST_ENTRY *</em> <strong>history_get</strong> <em>(int offset)</em><a href='#index-history_005fget' class='copiable-anchor'> &para;</a></span></dt>
+<dd><p>Return the history entry at position <var>offset</var>.
+The range of valid
+values of <var>offset</var> starts at <code>history_base</code> and ends at
+<var>history_length</var> - 1 (see <a href="#History-Variables">History Variables</a>).
+If there is no entry there, or if <var>offset</var> is outside the valid
+range, return a <code>NULL</code> pointer.
+</p></dd></dl>
+
+<dl class="def">
+<dt id="index-history_005fget_005ftime"><span class="category">Function: </span><span><em>time_t</em> <strong>history_get_time</strong> <em>(HIST_ENTRY *entry)</em><a href='#index-history_005fget_005ftime' class='copiable-anchor'> &para;</a></span></dt>
+<dd><p>Return the time stamp associated with the history entry <var>entry</var>.
+If the timestamp is missing or invalid, return 0.
+</p></dd></dl>
+
+<dl class="def">
+<dt id="index-history_005ftotal_005fbytes"><span class="category">Function: </span><span><em>int</em> <strong>history_total_bytes</strong> <em>(void)</em><a href='#index-history_005ftotal_005fbytes' class='copiable-anchor'> &para;</a></span></dt>
+<dd><p>Return the number of bytes that the primary history entries are using.
+This function returns the sum of the lengths of all the lines in the
+history.
+</p></dd></dl>
+
+<hr>
+</div>
+<div class="subsection" id="Moving-Around-the-History-List">
+<div class="header">
+<p>
+Next: <a href="#Searching-the-History-List" accesskey="n" rel="next">Searching the History List</a>, Previous: <a href="#Information-About-the-History-List" accesskey="p" rel="prev">Information About the History List</a>, Up: <a href="#History-Functions" accesskey="u" rel="up">History Functions</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Concept-Index" title="Index" rel="index">Index</a>]</p>
+</div>
+<span id="Moving-Around-the-History-List-1"></span><h4 class="subsection">2.3.4 Moving Around the History List</h4>
+
+<p>These functions allow the current index into the history list to be
+set or changed.
+</p>
+<dl class="def">
+<dt id="index-history_005fset_005fpos"><span class="category">Function: </span><span><em>int</em> <strong>history_set_pos</strong> <em>(int pos)</em><a href='#index-history_005fset_005fpos' class='copiable-anchor'> &para;</a></span></dt>
+<dd><p>Set the current history offset to <var>pos</var>, an absolute index
+into the list.
+Returns 1 on success, 0 if <var>pos</var> is less than zero or greater
+than the number of history entries.
+</p></dd></dl>
+
+<dl class="def">
+<dt id="index-previous_005fhistory"><span class="category">Function: </span><span><em>HIST_ENTRY *</em> <strong>previous_history</strong> <em>(void)</em><a href='#index-previous_005fhistory' class='copiable-anchor'> &para;</a></span></dt>
+<dd><p>Back up the current history offset to the previous history entry, and
+return a pointer to that entry. If there is no previous entry, return
+a <code>NULL</code> pointer.
+</p></dd></dl>
+
+<dl class="def">
+<dt id="index-next_005fhistory"><span class="category">Function: </span><span><em>HIST_ENTRY *</em> <strong>next_history</strong> <em>(void)</em><a href='#index-next_005fhistory' class='copiable-anchor'> &para;</a></span></dt>
+<dd><p>If the current history offset refers to a valid history entry,
+increment the current history offset.
+If the possibly-incremented history offset refers to a valid history
+entry, return a pointer to that entry;
+otherwise, return a <code>BNULL</code> pointer.
+</p></dd></dl>
+
+<hr>
+</div>
+<div class="subsection" id="Searching-the-History-List">
+<div class="header">
+<p>
+Next: <a href="#Managing-the-History-File" accesskey="n" rel="next">Managing the History File</a>, Previous: <a href="#Moving-Around-the-History-List" accesskey="p" rel="prev">Moving Around the History List</a>, Up: <a href="#History-Functions" accesskey="u" rel="up">History Functions</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Concept-Index" title="Index" rel="index">Index</a>]</p>
+</div>
+<span id="Searching-the-History-List-1"></span><h4 class="subsection">2.3.5 Searching the History List</h4>
+<span id="index-History-Searching"></span>
+
+<p>These functions allow searching of the history list for entries containing
+a specific string. Searching may be performed both forward and backward
+from the current history position. The search may be <em>anchored</em>,
+meaning that the string must match at the beginning of the history entry.
+<span id="index-anchored-search"></span>
+</p>
+<dl class="def">
+<dt id="index-history_005fsearch"><span class="category">Function: </span><span><em>int</em> <strong>history_search</strong> <em>(const char *string, int direction)</em><a href='#index-history_005fsearch' class='copiable-anchor'> &para;</a></span></dt>
+<dd><p>Search the history for <var>string</var>, starting at the current history offset.
+If <var>direction</var> is less than 0, then the search is through
+previous entries, otherwise through subsequent entries.
+If <var>string</var> is found, then
+the current history index is set to that history entry, and the value
+returned is the offset in the line of the entry where
+<var>string</var> was found. Otherwise, nothing is changed, and a -1 is
+returned.
+</p></dd></dl>
+
+<dl class="def">
+<dt id="index-history_005fsearch_005fprefix"><span class="category">Function: </span><span><em>int</em> <strong>history_search_prefix</strong> <em>(const char *string, int direction)</em><a href='#index-history_005fsearch_005fprefix' class='copiable-anchor'> &para;</a></span></dt>
+<dd><p>Search the history for <var>string</var>, starting at the current history
+offset. The search is anchored: matching lines must begin with
+<var>string</var>. If <var>direction</var> is less than 0, then the search is
+through previous entries, otherwise through subsequent entries.
+If <var>string</var> is found, then the
+current history index is set to that entry, and the return value is 0.
+Otherwise, nothing is changed, and a -1 is returned.
+</p></dd></dl>
+
+<dl class="def">
+<dt id="index-history_005fsearch_005fpos"><span class="category">Function: </span><span><em>int</em> <strong>history_search_pos</strong> <em>(const char *string, int direction, int pos)</em><a href='#index-history_005fsearch_005fpos' class='copiable-anchor'> &para;</a></span></dt>
+<dd><p>Search for <var>string</var> in the history list, starting at <var>pos</var>, an
+absolute index into the list. If <var>direction</var> is negative, the search
+proceeds backward from <var>pos</var>, otherwise forward. Returns the absolute
+index of the history element where <var>string</var> was found, or -1 otherwise.
+</p></dd></dl>
+
+<hr>
+</div>
+<div class="subsection" id="Managing-the-History-File">
+<div class="header">
+<p>
+Next: <a href="#History-Expansion" accesskey="n" rel="next">History Expansion</a>, Previous: <a href="#Searching-the-History-List" accesskey="p" rel="prev">Searching the History List</a>, Up: <a href="#History-Functions" accesskey="u" rel="up">History Functions</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Concept-Index" title="Index" rel="index">Index</a>]</p>
+</div>
+<span id="Managing-the-History-File-1"></span><h4 class="subsection">2.3.6 Managing the History File</h4>
+
+<p>The History library can read the history from and write it to a file.
+This section documents the functions for managing a history file.
+</p>
+<dl class="def">
+<dt id="index-read_005fhistory"><span class="category">Function: </span><span><em>int</em> <strong>read_history</strong> <em>(const char *filename)</em><a href='#index-read_005fhistory' class='copiable-anchor'> &para;</a></span></dt>
+<dd><p>Add the contents of <var>filename</var> to the history list, a line at a time.
+If <var>filename</var> is <code>NULL</code>, then read from <samp>~/.history</samp>.
+Returns 0 if successful, or <code>errno</code> if not.
+</p></dd></dl>
+
+<dl class="def">
+<dt id="index-read_005fhistory_005frange"><span class="category">Function: </span><span><em>int</em> <strong>read_history_range</strong> <em>(const char *filename, int from, int to)</em><a href='#index-read_005fhistory_005frange' class='copiable-anchor'> &para;</a></span></dt>
+<dd><p>Read a range of lines from <var>filename</var>, adding them to the history list.
+Start reading at line <var>from</var> and end at <var>to</var>.
+If <var>from</var> is zero, start at the beginning. If <var>to</var> is less than
+<var>from</var>, then read until the end of the file. If <var>filename</var> is
+<code>NULL</code>, then read from <samp>~/.history</samp>. Returns 0 if successful,
+or <code>errno</code> if not.
+</p></dd></dl>
+
+<dl class="def">
+<dt id="index-write_005fhistory"><span class="category">Function: </span><span><em>int</em> <strong>write_history</strong> <em>(const char *filename)</em><a href='#index-write_005fhistory' class='copiable-anchor'> &para;</a></span></dt>
+<dd><p>Write the current history to <var>filename</var>, overwriting <var>filename</var>
+if necessary.
+If <var>filename</var> is <code>NULL</code>, then write the history list to
+<samp>~/.history</samp>.
+Returns 0 on success, or <code>errno</code> on a read or write error.
+</p></dd></dl>
+
+<dl class="def">
+<dt id="index-append_005fhistory"><span class="category">Function: </span><span><em>int</em> <strong>append_history</strong> <em>(int nelements, const char *filename)</em><a href='#index-append_005fhistory' class='copiable-anchor'> &para;</a></span></dt>
+<dd><p>Append the last <var>nelements</var> of the history list to <var>filename</var>.
+If <var>filename</var> is <code>NULL</code>, then append to <samp>~/.history</samp>.
+Returns 0 on success, or <code>errno</code> on a read or write error.
+</p></dd></dl>
+
+<dl class="def">
+<dt id="index-history_005ftruncate_005ffile"><span class="category">Function: </span><span><em>int</em> <strong>history_truncate_file</strong> <em>(const char *filename, int nlines)</em><a href='#index-history_005ftruncate_005ffile' class='copiable-anchor'> &para;</a></span></dt>
+<dd><p>Truncate the history file <var>filename</var>, leaving only the last
+<var>nlines</var> lines.
+If <var>filename</var> is <code>NULL</code>, then <samp>~/.history</samp> is truncated.
+Returns 0 on success, or <code>errno</code> on failure.
+</p></dd></dl>
+
+<hr>
+</div>
+<div class="subsection" id="History-Expansion">
+<div class="header">
+<p>
+Previous: <a href="#Managing-the-History-File" accesskey="p" rel="prev">Managing the History File</a>, Up: <a href="#History-Functions" accesskey="u" rel="up">History Functions</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Concept-Index" title="Index" rel="index">Index</a>]</p>
+</div>
+<span id="History-Expansion-2"></span><h4 class="subsection">2.3.7 History Expansion</h4>
+
+<p>These functions implement history expansion.
+</p>
+<dl class="def">
+<dt id="index-history_005fexpand"><span class="category">Function: </span><span><em>int</em> <strong>history_expand</strong> <em>(char *string, char **output)</em><a href='#index-history_005fexpand' class='copiable-anchor'> &para;</a></span></dt>
+<dd><p>Expand <var>string</var>, placing the result into <var>output</var>, a pointer
+to a string (see <a href="#History-Interaction">History Expansion</a>). Returns:
+</p><dl compact="compact">
+<dt><span><code>0</code></span></dt>
+<dd><p>If no expansions took place (or, if the only change in
+the text was the removal of escape characters preceding the history expansion
+character);
+</p></dd>
+<dt><span><code>1</code></span></dt>
+<dd><p>if expansions did take place;
+</p></dd>
+<dt><span><code>-1</code></span></dt>
+<dd><p>if there was an error in expansion;
+</p></dd>
+<dt><span><code>2</code></span></dt>
+<dd><p>if the returned line should be displayed, but not executed,
+as with the <code>:p</code> modifier (see <a href="#Modifiers">Modifiers</a>).
+</p></dd>
+</dl>
+
+<p>If an error occurred in expansion, then <var>output</var> contains a descriptive
+error message.
+</p></dd></dl>
+
+<dl class="def">
+<dt id="index-get_005fhistory_005fevent"><span class="category">Function: </span><span><em>char *</em> <strong>get_history_event</strong> <em>(const char *string, int *cindex, int qchar)</em><a href='#index-get_005fhistory_005fevent' class='copiable-anchor'> &para;</a></span></dt>
+<dd><p>Returns the text of the history event beginning at <var>string</var> +
+<var>*cindex</var>. <var>*cindex</var> is modified to point to after the event
+specifier. At function entry, <var>cindex</var> points to the index into
+<var>string</var> where the history event specification begins. <var>qchar</var>
+is a character that is allowed to end the event specification in addition
+to the &ldquo;normal&rdquo; terminating characters.
+</p></dd></dl>
+
+<dl class="def">
+<dt id="index-history_005ftokenize"><span class="category">Function: </span><span><em>char **</em> <strong>history_tokenize</strong> <em>(const char *string)</em><a href='#index-history_005ftokenize' class='copiable-anchor'> &para;</a></span></dt>
+<dd><p>Return an array of tokens parsed out of <var>string</var>, much as the
+shell might. The tokens are split on the characters in the
+<var>history_word_delimiters</var> variable,
+and shell quoting conventions are obeyed as described below.
+</p></dd></dl>
+
+<dl class="def">
+<dt id="index-history_005farg_005fextract"><span class="category">Function: </span><span><em>char *</em> <strong>history_arg_extract</strong> <em>(int first, int last, const char *string)</em><a href='#index-history_005farg_005fextract' class='copiable-anchor'> &para;</a></span></dt>
+<dd><p>Extract a string segment consisting of the <var>first</var> through <var>last</var>
+arguments present in <var>string</var>. Arguments are split using
+<code>history_tokenize</code>.
+</p></dd></dl>
+
+<hr>
+</div>
+</div>
+<div class="section" id="History-Variables">
+<div class="header">
+<p>
+Next: <a href="#History-Programming-Example" accesskey="n" rel="next">History Programming Example</a>, Previous: <a href="#History-Functions" accesskey="p" rel="prev">History Functions</a>, Up: <a href="#Programming-with-GNU-History" accesskey="u" rel="up">Programming with GNU History</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Concept-Index" title="Index" rel="index">Index</a>]</p>
+</div>
+<span id="History-Variables-1"></span><h3 class="section">2.4 History Variables</h3>
+
+<p>This section describes the externally-visible variables exported by
+the <small>GNU</small> History Library.
+</p>
+<dl class="def">
+<dt id="index-history_005fbase"><span class="category">Variable: </span><span><em>int</em> <strong>history_base</strong><a href='#index-history_005fbase' class='copiable-anchor'> &para;</a></span></dt>
+<dd><p>The logical offset of the first entry in the history list.
+</p></dd></dl>
+
+<dl class="def">
+<dt id="index-history_005flength"><span class="category">Variable: </span><span><em>int</em> <strong>history_length</strong><a href='#index-history_005flength' class='copiable-anchor'> &para;</a></span></dt>
+<dd><p>The number of entries currently stored in the history list.
+</p></dd></dl>
+
+<dl class="def">
+<dt id="index-history_005fmax_005fentries"><span class="category">Variable: </span><span><em>int</em> <strong>history_max_entries</strong><a href='#index-history_005fmax_005fentries' class='copiable-anchor'> &para;</a></span></dt>
+<dd><p>The maximum number of history entries. This must be changed using
+<code>stifle_history()</code>.
+</p></dd></dl>
+
+<dl class="def">
+<dt id="index-history_005fwrite_005ftimestamps"><span class="category">Variable: </span><span><em>int</em> <strong>history_write_timestamps</strong><a href='#index-history_005fwrite_005ftimestamps' class='copiable-anchor'> &para;</a></span></dt>
+<dd><p>If non-zero, timestamps are written to the history file, so they can be
+preserved between sessions. The default value is 0, meaning that
+timestamps are not saved.
+</p>
+<p>The current timestamp format uses the value of <var>history_comment_char</var>
+to delimit timestamp entries in the history file. If that variable does
+not have a value (the default), timestamps will not be written.
+</p></dd></dl>
+
+<dl class="def">
+<dt id="index-history_005fexpansion_005fchar"><span class="category">Variable: </span><span><em>char</em> <strong>history_expansion_char</strong><a href='#index-history_005fexpansion_005fchar' class='copiable-anchor'> &para;</a></span></dt>
+<dd><p>The character that introduces a history event. The default is &lsquo;<samp>!</samp>&rsquo;.
+Setting this to 0 inhibits history expansion.
+</p></dd></dl>
+
+<dl class="def">
+<dt id="index-history_005fsubst_005fchar"><span class="category">Variable: </span><span><em>char</em> <strong>history_subst_char</strong><a href='#index-history_005fsubst_005fchar' class='copiable-anchor'> &para;</a></span></dt>
+<dd><p>The character that invokes word substitution if found at the start of
+a line. The default is &lsquo;<samp>^</samp>&rsquo;.
+</p></dd></dl>
+
+<dl class="def">
+<dt id="index-history_005fcomment_005fchar"><span class="category">Variable: </span><span><em>char</em> <strong>history_comment_char</strong><a href='#index-history_005fcomment_005fchar' class='copiable-anchor'> &para;</a></span></dt>
+<dd><p>During tokenization, if this character is seen as the first character
+of a word, then it and all subsequent characters up to a newline are
+ignored, suppressing history expansion for the remainder of the line.
+This is disabled by default.
+</p></dd></dl>
+
+<dl class="def">
+<dt id="index-history_005fword_005fdelimiters"><span class="category">Variable: </span><span><em>char *</em> <strong>history_word_delimiters</strong><a href='#index-history_005fword_005fdelimiters' class='copiable-anchor'> &para;</a></span></dt>
+<dd><p>The characters that separate tokens for <code>history_tokenize()</code>.
+The default value is <code>&quot; \t\n()&lt;&gt;;&amp;|&quot;</code>.
+</p></dd></dl>
+
+<dl class="def">
+<dt id="index-history_005fsearch_005fdelimiter_005fchars"><span class="category">Variable: </span><span><em>char *</em> <strong>history_search_delimiter_chars</strong><a href='#index-history_005fsearch_005fdelimiter_005fchars' class='copiable-anchor'> &para;</a></span></dt>
+<dd><p>The list of additional characters which can delimit a history search
+string, in addition to space, TAB, &lsquo;<samp>:</samp>&rsquo; and &lsquo;<samp>?</samp>&rsquo; in the case of
+a substring search. The default is empty.
+</p></dd></dl>
+
+<dl class="def">
+<dt id="index-history_005fno_005fexpand_005fchars"><span class="category">Variable: </span><span><em>char *</em> <strong>history_no_expand_chars</strong><a href='#index-history_005fno_005fexpand_005fchars' class='copiable-anchor'> &para;</a></span></dt>
+<dd><p>The list of characters which inhibit history expansion if found immediately
+following <var>history_expansion_char</var>. The default is space, tab, newline,
+carriage return, and &lsquo;<samp>=</samp>&rsquo;.
+</p></dd></dl>
+
+<dl class="def">
+<dt id="index-history_005fquotes_005finhibit_005fexpansion"><span class="category">Variable: </span><span><em>int</em> <strong>history_quotes_inhibit_expansion</strong><a href='#index-history_005fquotes_005finhibit_005fexpansion' class='copiable-anchor'> &para;</a></span></dt>
+<dd><p>If non-zero, the history expansion code implements shell-like quoting:
+single-quoted words are not scanned for the history expansion
+character or the history comment character, and double-quoted words may
+have history expansion performed, since single quotes are not special
+within double quotes.
+The default value is 0.
+</p></dd></dl>
+
+<dl class="def">
+<dt id="index-history_005fquoting_005fstate"><span class="category">Variable: </span><span><em>int</em> <strong>history_quoting_state</strong><a href='#index-history_005fquoting_005fstate' class='copiable-anchor'> &para;</a></span></dt>
+<dd><p>An application may set this variable to indicate that the current line
+being expanded is subject to existing quoting. If set to &lsquo;<samp>'</samp>&rsquo;, the
+history expansion function will assume that the line is single-quoted and
+inhibit expansion until it reads an unquoted closing single quote; if set
+to &lsquo;<samp>&quot;</samp>&rsquo;, history expansion will assume the line is double quoted until
+it reads an unquoted closing double quote. If set to zero, the default,
+the history expansion function will assume the line is not quoted and
+treat quote characters within the line as described above.
+This is only effective if <var>history_quotes_inhibit_expansion</var> is set.
+</p></dd></dl>
+
+<dl class="def">
+<dt id="index-history_005finhibit_005fexpansion_005ffunction"><span class="category">Variable: </span><span><em>rl_linebuf_func_t *</em> <strong>history_inhibit_expansion_function</strong><a href='#index-history_005finhibit_005fexpansion_005ffunction' class='copiable-anchor'> &para;</a></span></dt>
+<dd><p>This should be set to the address of a function that takes two arguments:
+a <code>char *</code> (<var>string</var>)
+and an <code>int</code> index into that string (<var>i</var>).
+It should return a non-zero value if the history expansion starting at
+<var>string[i]</var> should not be performed; zero if the expansion should
+be done.
+It is intended for use by applications like Bash that use the history
+expansion character for additional purposes.
+By default, this variable is set to <code>NULL</code>.
+</p></dd></dl>
+
+<hr>
+</div>
+<div class="section" id="History-Programming-Example">
+<div class="header">
+<p>
+Previous: <a href="#History-Variables" accesskey="p" rel="prev">History Variables</a>, Up: <a href="#Programming-with-GNU-History" accesskey="u" rel="up">Programming with GNU History</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Concept-Index" title="Index" rel="index">Index</a>]</p>
+</div>
+<span id="History-Programming-Example-1"></span><h3 class="section">2.5 History Programming Example</h3>
+
+<p>The following program demonstrates simple use of the <small>GNU</small> History Library.
+</p>
+<div class="example">
+<pre class="example">#include &lt;stdio.h&gt;
+#include &lt;readline/history.h&gt;
+
+main (argc, argv)
+ int argc;
+ char **argv;
+{
+ char line[1024], *t;
+ int len, done = 0;
+
+ line[0] = 0;
+
+ using_history ();
+ while (!done)
+ {
+ printf (&quot;history$ &quot;);
+ fflush (stdout);
+ t = fgets (line, sizeof (line) - 1, stdin);
+ if (t &amp;&amp; *t)
+ {
+ len = strlen (t);
+ if (t[len - 1] == '\n')
+ t[len - 1] = '\0';
+ }
+
+ if (!t)
+ strcpy (line, &quot;quit&quot;);
+
+ if (line[0])
+ {
+ char *expansion;
+ int result;
+
+ result = history_expand (line, &amp;expansion);
+ if (result)
+ fprintf (stderr, &quot;%s\n&quot;, expansion);
+
+ if (result &lt; 0 || result == 2)
+ {
+ free (expansion);
+ continue;
+ }
+
+ add_history (expansion);
+ strncpy (line, expansion, sizeof (line) - 1);
+ free (expansion);
+ }
+
+ if (strcmp (line, &quot;quit&quot;) == 0)
+ done = 1;
+ else if (strcmp (line, &quot;save&quot;) == 0)
+ write_history (&quot;history_file&quot;);
+ else if (strcmp (line, &quot;read&quot;) == 0)
+ read_history (&quot;history_file&quot;);
+ else if (strcmp (line, &quot;list&quot;) == 0)
+ {
+ register HIST_ENTRY **the_list;
+ register int i;
+
+ the_list = history_list ();
+ if (the_list)
+ for (i = 0; the_list[i]; i++)
+ printf (&quot;%d: %s\n&quot;, i + history_base, the_list[i]-&gt;line);
+ }
+ else if (strncmp (line, &quot;delete&quot;, 6) == 0)
+ {
+ int which;
+ if ((sscanf (line + 6, &quot;%d&quot;, &amp;which)) == 1)
+ {
+ HIST_ENTRY *entry = remove_history (which);
+ if (!entry)
+ fprintf (stderr, &quot;No such entry %d\n&quot;, which);
+ else
+ {
+ free (entry-&gt;line);
+ free (entry);
+ }
+ }
+ else
+ {
+ fprintf (stderr, &quot;non-numeric arg given to `delete'\n&quot;);
+ }
+ }
+ }
+}
+</pre></div>
+
+<hr>
+</div>
+</div>
+<div class="appendix" id="GNU-Free-Documentation-License">
+<div class="header">
+<p>
+Next: <a href="#Concept-Index" accesskey="n" rel="next">Concept Index</a>, Previous: <a href="#Programming-with-GNU-History" accesskey="p" rel="prev">Programming with GNU History</a>, Up: <a href="#Top" accesskey="u" rel="up">GNU History Library</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Concept-Index" title="Index" rel="index">Index</a>]</p>
+</div>
+<span id="GNU-Free-Documentation-License-1"></span><h2 class="appendix">Appendix A GNU Free Documentation License</h2>
+
+<div align="center">Version 1.3, 3 November 2008
+</div>
+
+<div class="display">
+<pre class="display">Copyright &copy; 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc.
+<a href="http://fsf.org/">http://fsf.org/</a>
+
+Everyone is permitted to copy and distribute verbatim copies
+of this license document, but changing it is not allowed.
+</pre></div>
+
+<ol start="0">
+<li> PREAMBLE
+
+<p>The purpose of this License is to make a manual, textbook, or other
+functional and useful document <em>free</em> in the sense of freedom: to
+assure everyone the effective freedom to copy and redistribute it,
+with or without modifying it, either commercially or noncommercially.
+Secondarily, this License preserves for the author and publisher a way
+to get credit for their work, while not being considered responsible
+for modifications made by others.
+</p>
+<p>This License is a kind of &ldquo;copyleft&rdquo;, which means that derivative
+works of the document must themselves be free in the same sense. It
+complements the GNU General Public License, which is a copyleft
+license designed for free software.
+</p>
+<p>We have designed this License in order to use it for manuals for free
+software, because free software needs free documentation: a free
+program should come with manuals providing the same freedoms that the
+software does. But this License is not limited to software manuals;
+it can be used for any textual work, regardless of subject matter or
+whether it is published as a printed book. We recommend this License
+principally for works whose purpose is instruction or reference.
+</p>
+</li><li> APPLICABILITY AND DEFINITIONS
+
+<p>This License applies to any manual or other work, in any medium, that
+contains a notice placed by the copyright holder saying it can be
+distributed under the terms of this License. Such a notice grants a
+world-wide, royalty-free license, unlimited in duration, to use that
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+refers to any such manual or work. Any member of the public is a
+licensee, and is addressed as &ldquo;you&rdquo;. You accept the license if you
+copy, modify or distribute the work in a way requiring permission
+under copyright law.
+</p>
+<p>A &ldquo;Modified Version&rdquo; of the Document means any work containing the
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+<p>A &ldquo;Secondary Section&rdquo; is a named appendix or a front-matter section
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+Sections then there are none.
+</p>
+<p>The &ldquo;Cover Texts&rdquo; are certain short passages of text that are listed,
+as Front-Cover Texts or Back-Cover Texts, in the notice that says that
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+</p>
+<p>A &ldquo;Transparent&rdquo; copy of the Document means a machine-readable copy,
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+or discourage subsequent modification by readers is not Transparent.
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+of text. A copy that is not &ldquo;Transparent&rdquo; is called &ldquo;Opaque&rdquo;.
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+</p>
+<p>The Document may include Warranty Disclaimers next to the notice which
+states that this License applies to the Document. These Warranty
+Disclaimers are considered to be included by reference in this
+License, but only as regards disclaiming warranties: any other
+implication that these Warranty Disclaimers may have is void and has
+no effect on the meaning of this License.
+</p>
+</li><li> VERBATIM COPYING
+
+<p>You may copy and distribute the Document in any medium, either
+commercially or noncommercially, provided that this License, the
+copyright notices, and the license notice saying this License applies
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+conditions whatsoever to those of this License. You may not use
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+</p>
+<p>You may also lend copies, under the same conditions stated above, and
+you may publicly display copies.
+</p>
+</li><li> COPYING IN QUANTITY
+
+<p>If you publish printed copies (or copies in media that commonly have
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+Document&rsquo;s license notice requires Cover Texts, you must enclose the
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+Copying with changes limited to the covers, as long as they preserve
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+as verbatim copying in other respects.
+</p>
+<p>If the required texts for either cover are too voluminous to fit
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+</p>
+<p>If you publish or distribute Opaque copies of the Document numbering
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+</li><li> MODIFICATIONS
+
+<p>You may copy and distribute a Modified Version of the Document under
+the conditions of sections 2 and 3 above, provided that you release
+the Modified Version under precisely this License, with the Modified
+Version filling the role of the Document, thus licensing distribution
+and modification of the Modified Version to whoever possesses a copy
+of it. In addition, you must do these things in the Modified Version:
+</p>
+<ol type="A" start="1">
+<li> Use in the Title Page (and on the covers, if any) a title distinct
+from that of the Document, and from those of previous versions
+(which should, if there were any, be listed in the History section
+of the Document). You may use the same title as a previous version
+if the original publisher of that version gives permission.
+
+</li><li> List on the Title Page, as authors, one or more persons or entities
+responsible for authorship of the modifications in the Modified
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+Document (all of its principal authors, if it has fewer than five),
+unless they release you from this requirement.
+
+</li><li> State on the Title page the name of the publisher of the
+Modified Version, as the publisher.
+
+</li><li> Preserve all the copyright notices of the Document.
+
+</li><li> Add an appropriate copyright notice for your modifications
+adjacent to the other copyright notices.
+
+</li><li> Include, immediately after the copyright notices, a license notice
+giving the public permission to use the Modified Version under the
+terms of this License, in the form shown in the Addendum below.
+
+</li><li> Preserve in that license notice the full lists of Invariant Sections
+and required Cover Texts given in the Document&rsquo;s license notice.
+
+</li><li> Include an unaltered copy of this License.
+
+</li><li> Preserve the section Entitled &ldquo;History&rdquo;, Preserve its Title, and add
+to it an item stating at least the title, year, new authors, and
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+
+</li><li> Preserve the network location, if any, given in the Document for
+public access to a Transparent copy of the Document, and likewise
+the network locations given in the Document for previous versions
+it was based on. These may be placed in the &ldquo;History&rdquo; section.
+You may omit a network location for a work that was published at
+least four years before the Document itself, or if the original
+publisher of the version it refers to gives permission.
+
+</li><li> For any section Entitled &ldquo;Acknowledgements&rdquo; or &ldquo;Dedications&rdquo;, Preserve
+the Title of the section, and preserve in the section all the
+substance and tone of each of the contributor acknowledgements and/or
+dedications given therein.
+
+</li><li> Preserve all the Invariant Sections of the Document,
+unaltered in their text and in their titles. Section numbers
+or the equivalent are not considered part of the section titles.
+
+</li><li> Delete any section Entitled &ldquo;Endorsements&rdquo;. Such a section
+may not be included in the Modified Version.
+
+</li><li> Do not retitle any existing section to be Entitled &ldquo;Endorsements&rdquo; or
+to conflict in title with any Invariant Section.
+
+</li><li> Preserve any Warranty Disclaimers.
+</li></ol>
+
+<p>If the Modified Version includes new front-matter sections or
+appendices that qualify as Secondary Sections and contain no material
+copied from the Document, you may at your option designate some or all
+of these sections as invariant. To do this, add their titles to the
+list of Invariant Sections in the Modified Version&rsquo;s license notice.
+These titles must be distinct from any other section titles.
+</p>
+<p>You may add a section Entitled &ldquo;Endorsements&rdquo;, provided it contains
+nothing but endorsements of your Modified Version by various
+parties&mdash;for example, statements of peer review or that the text has
+been approved by an organization as the authoritative definition of a
+standard.
+</p>
+<p>You may add a passage of up to five words as a Front-Cover Text, and a
+passage of up to 25 words as a Back-Cover Text, to the end of the list
+of Cover Texts in the Modified Version. Only one passage of
+Front-Cover Text and one of Back-Cover Text may be added by (or
+through arrangements made by) any one entity. If the Document already
+includes a cover text for the same cover, previously added by you or
+by arrangement made by the same entity you are acting on behalf of,
+you may not add another; but you may replace the old one, on explicit
+permission from the previous publisher that added the old one.
+</p>
+<p>The author(s) and publisher(s) of the Document do not by this License
+give permission to use their names for publicity for or to assert or
+imply endorsement of any Modified Version.
+</p>
+</li><li> COMBINING DOCUMENTS
+
+<p>You may combine the Document with other documents released under this
+License, under the terms defined in section 4 above for modified
+versions, provided that you include in the combination all of the
+Invariant Sections of all of the original documents, unmodified, and
+list them all as Invariant Sections of your combined work in its
+license notice, and that you preserve all their Warranty Disclaimers.
+</p>
+<p>The combined work need only contain one copy of this License, and
+multiple identical Invariant Sections may be replaced with a single
+copy. If there are multiple Invariant Sections with the same name but
+different contents, make the title of each such section unique by
+adding at the end of it, in parentheses, the name of the original
+author or publisher of that section if known, or else a unique number.
+Make the same adjustment to the section titles in the list of
+Invariant Sections in the license notice of the combined work.
+</p>
+<p>In the combination, you must combine any sections Entitled &ldquo;History&rdquo;
+in the various original documents, forming one section Entitled
+&ldquo;History&rdquo;; likewise combine any sections Entitled &ldquo;Acknowledgements&rdquo;,
+and any sections Entitled &ldquo;Dedications&rdquo;. You must delete all
+sections Entitled &ldquo;Endorsements.&rdquo;
+</p>
+</li><li> COLLECTIONS OF DOCUMENTS
+
+<p>You may make a collection consisting of the Document and other documents
+released under this License, and replace the individual copies of this
+License in the various documents with a single copy that is included in
+the collection, provided that you follow the rules of this License for
+verbatim copying of each of the documents in all other respects.
+</p>
+<p>You may extract a single document from such a collection, and distribute
+it individually under this License, provided you insert a copy of this
+License into the extracted document, and follow this License in all
+other respects regarding verbatim copying of that document.
+</p>
+</li><li> AGGREGATION WITH INDEPENDENT WORKS
+
+<p>A compilation of the Document or its derivatives with other separate
+and independent documents or works, in or on a volume of a storage or
+distribution medium, is called an &ldquo;aggregate&rdquo; if the copyright
+resulting from the compilation is not used to limit the legal rights
+of the compilation&rsquo;s users beyond what the individual works permit.
+When the Document is included in an aggregate, this License does not
+apply to the other works in the aggregate which are not themselves
+derivative works of the Document.
+</p>
+<p>If the Cover Text requirement of section 3 is applicable to these
+copies of the Document, then if the Document is less than one half of
+the entire aggregate, the Document&rsquo;s Cover Texts may be placed on
+covers that bracket the Document within the aggregate, or the
+electronic equivalent of covers if the Document is in electronic form.
+Otherwise they must appear on printed covers that bracket the whole
+aggregate.
+</p>
+</li><li> TRANSLATION
+
+<p>Translation is considered a kind of modification, so you may
+distribute translations of the Document under the terms of section 4.
+Replacing Invariant Sections with translations requires special
+permission from their copyright holders, but you may include
+translations of some or all Invariant Sections in addition to the
+original versions of these Invariant Sections. You may include a
+translation of this License, and all the license notices in the
+Document, and any Warranty Disclaimers, provided that you also include
+the original English version of this License and the original versions
+of those notices and disclaimers. In case of a disagreement between
+the translation and the original version of this License or a notice
+or disclaimer, the original version will prevail.
+</p>
+<p>If a section in the Document is Entitled &ldquo;Acknowledgements&rdquo;,
+&ldquo;Dedications&rdquo;, or &ldquo;History&rdquo;, the requirement (section 4) to Preserve
+its Title (section 1) will typically require changing the actual
+title.
+</p>
+</li><li> TERMINATION
+
+<p>You may not copy, modify, sublicense, or distribute the Document
+except as expressly provided under this License. Any attempt
+otherwise to copy, modify, sublicense, or distribute it is void, and
+will automatically terminate your rights under this License.
+</p>
+<p>However, if you cease all violation of this License, then your license
+from a particular copyright holder is reinstated (a) provisionally,
+unless and until the copyright holder explicitly and finally
+terminates your license, and (b) permanently, if the copyright holder
+fails to notify you of the violation by some reasonable means prior to
+60 days after the cessation.
+</p>
+<p>Moreover, your license from a particular copyright holder is
+reinstated permanently if the copyright holder notifies you of the
+violation by some reasonable means, this is the first time you have
+received notice of violation of this License (for any work) from that
+copyright holder, and you cure the violation prior to 30 days after
+your receipt of the notice.
+</p>
+<p>Termination of your rights under this section does not terminate the
+licenses of parties who have received copies or rights from you under
+this License. If your rights have been terminated and not permanently
+reinstated, receipt of a copy of some or all of the same material does
+not give you any rights to use it.
+</p>
+</li><li> FUTURE REVISIONS OF THIS LICENSE
+
+<p>The Free Software Foundation may publish new, revised versions
+of the GNU Free Documentation License from time to time. Such new
+versions will be similar in spirit to the present version, but may
+differ in detail to address new problems or concerns. See
+<a href="http://www.gnu.org/copyleft/">http://www.gnu.org/copyleft/</a>.
+</p>
+<p>Each version of the License is given a distinguishing version number.
+If the Document specifies that a particular numbered version of this
+License &ldquo;or any later version&rdquo; applies to it, you have the option of
+following the terms and conditions either of that specified version or
+of any later version that has been published (not as a draft) by the
+Free Software Foundation. If the Document does not specify a version
+number of this License, you may choose any version ever published (not
+as a draft) by the Free Software Foundation. If the Document
+specifies that a proxy can decide which future versions of this
+License can be used, that proxy&rsquo;s public statement of acceptance of a
+version permanently authorizes you to choose that version for the
+Document.
+</p>
+</li><li> RELICENSING
+
+<p>&ldquo;Massive Multiauthor Collaboration Site&rdquo; (or &ldquo;MMC Site&rdquo;) means any
+World Wide Web server that publishes copyrightable works and also
+provides prominent facilities for anybody to edit those works. A
+public wiki that anybody can edit is an example of such a server. A
+&ldquo;Massive Multiauthor Collaboration&rdquo; (or &ldquo;MMC&rdquo;) contained in the
+site means any set of copyrightable works thus published on the MMC
+site.
+</p>
+<p>&ldquo;CC-BY-SA&rdquo; means the Creative Commons Attribution-Share Alike 3.0
+license published by Creative Commons Corporation, a not-for-profit
+corporation with a principal place of business in San Francisco,
+California, as well as future copyleft versions of that license
+published by that same organization.
+</p>
+<p>&ldquo;Incorporate&rdquo; means to publish or republish a Document, in whole or
+in part, as part of another Document.
+</p>
+<p>An MMC is &ldquo;eligible for relicensing&rdquo; if it is licensed under this
+License, and if all works that were first published under this License
+somewhere other than this MMC, and subsequently incorporated in whole
+or in part into the MMC, (1) had no cover texts or invariant sections,
+and (2) were thus incorporated prior to November 1, 2008.
+</p>
+<p>The operator of an MMC Site may republish an MMC contained in the site
+under CC-BY-SA on the same site at any time before August 1, 2009,
+provided the MMC is eligible for relicensing.
+</p>
+</li></ol>
+
+<span id="ADDENDUM_003a-How-to-use-this-License-for-your-documents"></span><h3 class="heading">ADDENDUM: How to use this License for your documents</h3>
+
+<p>To use this License in a document you have written, include a copy of
+the License in the document and put the following copyright and
+license notices just after the title page:
+</p>
+<div class="example">
+<pre class="example"> Copyright (C) <var>year</var> <var>your name</var>.
+ Permission is granted to copy, distribute and/or modify this document
+ under the terms of the GNU Free Documentation License, Version 1.3
+ or any later version published by the Free Software Foundation;
+ with no Invariant Sections, no Front-Cover Texts, and no Back-Cover
+ Texts. A copy of the license is included in the section entitled ``GNU
+ Free Documentation License''.
+</pre></div>
+
+<p>If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts,
+replace the &ldquo;with&hellip;Texts.&rdquo; line with this:
+</p>
+<div class="example">
+<pre class="example"> with the Invariant Sections being <var>list their titles</var>, with
+ the Front-Cover Texts being <var>list</var>, and with the Back-Cover Texts
+ being <var>list</var>.
+</pre></div>
+
+<p>If you have Invariant Sections without Cover Texts, or some other
+combination of the three, merge those two alternatives to suit the
+situation.
+</p>
+<p>If your document contains nontrivial examples of program code, we
+recommend releasing these examples in parallel under your choice of
+free software license, such as the GNU General Public License,
+to permit their use in free software.
+</p>
+
+
+<hr>
+</div>
+<div class="appendix" id="Concept-Index">
+<div class="header">
+<p>
+Next: <a href="#Function-and-Variable-Index" accesskey="n" rel="next">Function and Variable Index</a>, Previous: <a href="#GNU-Free-Documentation-License" accesskey="p" rel="prev">GNU Free Documentation License</a>, Up: <a href="#Top" accesskey="u" rel="up">GNU History Library</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Concept-Index" title="Index" rel="index">Index</a>]</p>
+</div>
+<span id="Concept-Index-1"></span><h2 class="appendix">Appendix B Concept Index</h2>
+<table><tr><th valign="top">Jump to: &nbsp; </th><td><a class="summary-letter" href="#Concept-Index_cp_letter-A"><b>A</b></a>
+ &nbsp;
+<a class="summary-letter" href="#Concept-Index_cp_letter-E"><b>E</b></a>
+ &nbsp;
+<a class="summary-letter" href="#Concept-Index_cp_letter-H"><b>H</b></a>
+ &nbsp;
+</td></tr></table>
+<table class="index-cp" border="0">
+<tr><td></td><th align="left">Index Entry</th><td>&nbsp;</td><th align="left"> Section</th></tr>
+<tr><td colspan="4"> <hr></td></tr>
+<tr><th id="Concept-Index_cp_letter-A">A</th><td></td><td></td></tr>
+<tr><td></td><td valign="top"><a href="#index-anchored-search">anchored search</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Searching-the-History-List">Searching the History List</a></td></tr>
+<tr><td colspan="4"> <hr></td></tr>
+<tr><th id="Concept-Index_cp_letter-E">E</th><td></td><td></td></tr>
+<tr><td></td><td valign="top"><a href="#index-event-designators">event designators</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Event-Designators">Event Designators</a></td></tr>
+<tr><td colspan="4"> <hr></td></tr>
+<tr><th id="Concept-Index_cp_letter-H">H</th><td></td><td></td></tr>
+<tr><td></td><td valign="top"><a href="#index-history-events">history events</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Event-Designators">Event Designators</a></td></tr>
+<tr><td></td><td valign="top"><a href="#index-history-expansion">history expansion</a>:</td><td>&nbsp;</td><td valign="top"><a href="#History-Interaction">History Interaction</a></td></tr>
+<tr><td></td><td valign="top"><a href="#index-History-Searching">History Searching</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Searching-the-History-List">Searching the History List</a></td></tr>
+<tr><td colspan="4"> <hr></td></tr>
+</table>
+<table><tr><th valign="top">Jump to: &nbsp; </th><td><a class="summary-letter" href="#Concept-Index_cp_letter-A"><b>A</b></a>
+ &nbsp;
+<a class="summary-letter" href="#Concept-Index_cp_letter-E"><b>E</b></a>
+ &nbsp;
+<a class="summary-letter" href="#Concept-Index_cp_letter-H"><b>H</b></a>
+ &nbsp;
+</td></tr></table>
+
+<hr>
+</div>
+<div class="appendix" id="Function-and-Variable-Index">
+<div class="header">
+<p>
+Previous: <a href="#Concept-Index" accesskey="p" rel="prev">Concept Index</a>, Up: <a href="#Top" accesskey="u" rel="up">GNU History Library</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Concept-Index" title="Index" rel="index">Index</a>]</p>
+</div>
+<span id="Function-and-Variable-Index-1"></span><h2 class="appendix">Appendix C Function and Variable Index</h2>
+<table><tr><th valign="top">Jump to: &nbsp; </th><td><a class="summary-letter" href="#Function-and-Variable-Index_vr_letter-A"><b>A</b></a>
+ &nbsp;
+<a class="summary-letter" href="#Function-and-Variable-Index_vr_letter-C"><b>C</b></a>
+ &nbsp;
+<a class="summary-letter" href="#Function-and-Variable-Index_vr_letter-F"><b>F</b></a>
+ &nbsp;
+<a class="summary-letter" href="#Function-and-Variable-Index_vr_letter-G"><b>G</b></a>
+ &nbsp;
+<a class="summary-letter" href="#Function-and-Variable-Index_vr_letter-H"><b>H</b></a>
+ &nbsp;
+<a class="summary-letter" href="#Function-and-Variable-Index_vr_letter-N"><b>N</b></a>
+ &nbsp;
+<a class="summary-letter" href="#Function-and-Variable-Index_vr_letter-P"><b>P</b></a>
+ &nbsp;
+<a class="summary-letter" href="#Function-and-Variable-Index_vr_letter-R"><b>R</b></a>
+ &nbsp;
+<a class="summary-letter" href="#Function-and-Variable-Index_vr_letter-S"><b>S</b></a>
+ &nbsp;
+<a class="summary-letter" href="#Function-and-Variable-Index_vr_letter-U"><b>U</b></a>
+ &nbsp;
+<a class="summary-letter" href="#Function-and-Variable-Index_vr_letter-W"><b>W</b></a>
+ &nbsp;
+</td></tr></table>
+<table class="index-vr" border="0">
+<tr><td></td><th align="left">Index Entry</th><td>&nbsp;</td><th align="left"> Section</th></tr>
+<tr><td colspan="4"> <hr></td></tr>
+<tr><th id="Function-and-Variable-Index_vr_letter-A">A</th><td></td><td></td></tr>
+<tr><td></td><td valign="top"><a href="#index-add_005fhistory"><code>add_history</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#History-List-Management">History List Management</a></td></tr>
+<tr><td></td><td valign="top"><a href="#index-add_005fhistory_005ftime"><code>add_history_time</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#History-List-Management">History List Management</a></td></tr>
+<tr><td></td><td valign="top"><a href="#index-append_005fhistory"><code>append_history</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Managing-the-History-File">Managing the History File</a></td></tr>
+<tr><td colspan="4"> <hr></td></tr>
+<tr><th id="Function-and-Variable-Index_vr_letter-C">C</th><td></td><td></td></tr>
+<tr><td></td><td valign="top"><a href="#index-clear_005fhistory"><code>clear_history</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#History-List-Management">History List Management</a></td></tr>
+<tr><td></td><td valign="top"><a href="#index-current_005fhistory"><code>current_history</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Information-About-the-History-List">Information About the History List</a></td></tr>
+<tr><td colspan="4"> <hr></td></tr>
+<tr><th id="Function-and-Variable-Index_vr_letter-F">F</th><td></td><td></td></tr>
+<tr><td></td><td valign="top"><a href="#index-free_005fhistory_005fentry"><code>free_history_entry</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#History-List-Management">History List Management</a></td></tr>
+<tr><td colspan="4"> <hr></td></tr>
+<tr><th id="Function-and-Variable-Index_vr_letter-G">G</th><td></td><td></td></tr>
+<tr><td></td><td valign="top"><a href="#index-get_005fhistory_005fevent"><code>get_history_event</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#History-Expansion">History Expansion</a></td></tr>
+<tr><td colspan="4"> <hr></td></tr>
+<tr><th id="Function-and-Variable-Index_vr_letter-H">H</th><td></td><td></td></tr>
+<tr><td></td><td valign="top"><a href="#index-history_005farg_005fextract"><code>history_arg_extract</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#History-Expansion">History Expansion</a></td></tr>
+<tr><td></td><td valign="top"><a href="#index-history_005fbase"><code>history_base</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#History-Variables">History Variables</a></td></tr>
+<tr><td></td><td valign="top"><a href="#index-history_005fcomment_005fchar"><code>history_comment_char</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#History-Variables">History Variables</a></td></tr>
+<tr><td></td><td valign="top"><a href="#index-history_005fexpand"><code>history_expand</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#History-Expansion">History Expansion</a></td></tr>
+<tr><td></td><td valign="top"><a href="#index-history_005fexpansion_005fchar"><code>history_expansion_char</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#History-Variables">History Variables</a></td></tr>
+<tr><td></td><td valign="top"><a href="#index-history_005fget"><code>history_get</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Information-About-the-History-List">Information About the History List</a></td></tr>
+<tr><td></td><td valign="top"><a href="#index-history_005fget_005fhistory_005fstate"><code>history_get_history_state</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Initializing-History-and-State-Management">Initializing History and State Management</a></td></tr>
+<tr><td></td><td valign="top"><a href="#index-history_005fget_005ftime"><code>history_get_time</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Information-About-the-History-List">Information About the History List</a></td></tr>
+<tr><td></td><td valign="top"><a href="#index-history_005finhibit_005fexpansion_005ffunction"><code>history_inhibit_expansion_function</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#History-Variables">History Variables</a></td></tr>
+<tr><td></td><td valign="top"><a href="#index-history_005fis_005fstifled"><code>history_is_stifled</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#History-List-Management">History List Management</a></td></tr>
+<tr><td></td><td valign="top"><a href="#index-history_005flength"><code>history_length</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#History-Variables">History Variables</a></td></tr>
+<tr><td></td><td valign="top"><a href="#index-history_005flist"><code>history_list</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Information-About-the-History-List">Information About the History List</a></td></tr>
+<tr><td></td><td valign="top"><a href="#index-history_005fmax_005fentries"><code>history_max_entries</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#History-Variables">History Variables</a></td></tr>
+<tr><td></td><td valign="top"><a href="#index-history_005fno_005fexpand_005fchars"><code>history_no_expand_chars</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#History-Variables">History Variables</a></td></tr>
+<tr><td></td><td valign="top"><a href="#index-history_005fquotes_005finhibit_005fexpansion"><code>history_quotes_inhibit_expansion</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#History-Variables">History Variables</a></td></tr>
+<tr><td></td><td valign="top"><a href="#index-history_005fquoting_005fstate"><code>history_quoting_state</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#History-Variables">History Variables</a></td></tr>
+<tr><td></td><td valign="top"><a href="#index-history_005fsearch"><code>history_search</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Searching-the-History-List">Searching the History List</a></td></tr>
+<tr><td></td><td valign="top"><a href="#index-history_005fsearch_005fdelimiter_005fchars"><code>history_search_delimiter_chars</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#History-Variables">History Variables</a></td></tr>
+<tr><td></td><td valign="top"><a href="#index-history_005fsearch_005fpos"><code>history_search_pos</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Searching-the-History-List">Searching the History List</a></td></tr>
+<tr><td></td><td valign="top"><a href="#index-history_005fsearch_005fprefix"><code>history_search_prefix</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Searching-the-History-List">Searching the History List</a></td></tr>
+<tr><td></td><td valign="top"><a href="#index-history_005fset_005fhistory_005fstate"><code>history_set_history_state</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Initializing-History-and-State-Management">Initializing History and State Management</a></td></tr>
+<tr><td></td><td valign="top"><a href="#index-history_005fset_005fpos"><code>history_set_pos</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Moving-Around-the-History-List">Moving Around the History List</a></td></tr>
+<tr><td></td><td valign="top"><a href="#index-history_005fsubst_005fchar"><code>history_subst_char</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#History-Variables">History Variables</a></td></tr>
+<tr><td></td><td valign="top"><a href="#index-history_005ftokenize"><code>history_tokenize</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#History-Expansion">History Expansion</a></td></tr>
+<tr><td></td><td valign="top"><a href="#index-history_005ftotal_005fbytes"><code>history_total_bytes</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Information-About-the-History-List">Information About the History List</a></td></tr>
+<tr><td></td><td valign="top"><a href="#index-history_005ftruncate_005ffile"><code>history_truncate_file</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Managing-the-History-File">Managing the History File</a></td></tr>
+<tr><td></td><td valign="top"><a href="#index-history_005fword_005fdelimiters"><code>history_word_delimiters</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#History-Variables">History Variables</a></td></tr>
+<tr><td></td><td valign="top"><a href="#index-history_005fwrite_005ftimestamps"><code>history_write_timestamps</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#History-Variables">History Variables</a></td></tr>
+<tr><td colspan="4"> <hr></td></tr>
+<tr><th id="Function-and-Variable-Index_vr_letter-N">N</th><td></td><td></td></tr>
+<tr><td></td><td valign="top"><a href="#index-next_005fhistory"><code>next_history</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Moving-Around-the-History-List">Moving Around the History List</a></td></tr>
+<tr><td colspan="4"> <hr></td></tr>
+<tr><th id="Function-and-Variable-Index_vr_letter-P">P</th><td></td><td></td></tr>
+<tr><td></td><td valign="top"><a href="#index-previous_005fhistory"><code>previous_history</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Moving-Around-the-History-List">Moving Around the History List</a></td></tr>
+<tr><td colspan="4"> <hr></td></tr>
+<tr><th id="Function-and-Variable-Index_vr_letter-R">R</th><td></td><td></td></tr>
+<tr><td></td><td valign="top"><a href="#index-read_005fhistory"><code>read_history</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Managing-the-History-File">Managing the History File</a></td></tr>
+<tr><td></td><td valign="top"><a href="#index-read_005fhistory_005frange"><code>read_history_range</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Managing-the-History-File">Managing the History File</a></td></tr>
+<tr><td></td><td valign="top"><a href="#index-remove_005fhistory"><code>remove_history</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#History-List-Management">History List Management</a></td></tr>
+<tr><td></td><td valign="top"><a href="#index-replace_005fhistory_005fentry"><code>replace_history_entry</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#History-List-Management">History List Management</a></td></tr>
+<tr><td colspan="4"> <hr></td></tr>
+<tr><th id="Function-and-Variable-Index_vr_letter-S">S</th><td></td><td></td></tr>
+<tr><td></td><td valign="top"><a href="#index-stifle_005fhistory"><code>stifle_history</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#History-List-Management">History List Management</a></td></tr>
+<tr><td colspan="4"> <hr></td></tr>
+<tr><th id="Function-and-Variable-Index_vr_letter-U">U</th><td></td><td></td></tr>
+<tr><td></td><td valign="top"><a href="#index-unstifle_005fhistory"><code>unstifle_history</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#History-List-Management">History List Management</a></td></tr>
+<tr><td></td><td valign="top"><a href="#index-using_005fhistory"><code>using_history</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Initializing-History-and-State-Management">Initializing History and State Management</a></td></tr>
+<tr><td colspan="4"> <hr></td></tr>
+<tr><th id="Function-and-Variable-Index_vr_letter-W">W</th><td></td><td></td></tr>
+<tr><td></td><td valign="top"><a href="#index-where_005fhistory"><code>where_history</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Information-About-the-History-List">Information About the History List</a></td></tr>
+<tr><td></td><td valign="top"><a href="#index-write_005fhistory"><code>write_history</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Managing-the-History-File">Managing the History File</a></td></tr>
+<tr><td colspan="4"> <hr></td></tr>
+</table>
+<table><tr><th valign="top">Jump to: &nbsp; </th><td><a class="summary-letter" href="#Function-and-Variable-Index_vr_letter-A"><b>A</b></a>
+ &nbsp;
+<a class="summary-letter" href="#Function-and-Variable-Index_vr_letter-C"><b>C</b></a>
+ &nbsp;
+<a class="summary-letter" href="#Function-and-Variable-Index_vr_letter-F"><b>F</b></a>
+ &nbsp;
+<a class="summary-letter" href="#Function-and-Variable-Index_vr_letter-G"><b>G</b></a>
+ &nbsp;
+<a class="summary-letter" href="#Function-and-Variable-Index_vr_letter-H"><b>H</b></a>
+ &nbsp;
+<a class="summary-letter" href="#Function-and-Variable-Index_vr_letter-N"><b>N</b></a>
+ &nbsp;
+<a class="summary-letter" href="#Function-and-Variable-Index_vr_letter-P"><b>P</b></a>
+ &nbsp;
+<a class="summary-letter" href="#Function-and-Variable-Index_vr_letter-R"><b>R</b></a>
+ &nbsp;
+<a class="summary-letter" href="#Function-and-Variable-Index_vr_letter-S"><b>S</b></a>
+ &nbsp;
+<a class="summary-letter" href="#Function-and-Variable-Index_vr_letter-U"><b>U</b></a>
+ &nbsp;
+<a class="summary-letter" href="#Function-and-Variable-Index_vr_letter-W"><b>W</b></a>
+ &nbsp;
+</td></tr></table>
+
+</div>
+</div>
+
+
+
+</body>
+</html>