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<title>HTML Xref Link Basics (GNU Texinfo 6.7)</title>
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<span id="HTML-Xref-Link-Basics"></span><div class="header">
<p>
Next: <a href="HTML-Xref-Node-Name-Expansion.html" accesskey="n" rel="next">HTML Xref Node Name Expansion</a>, Up: <a href="HTML-Xref.html" accesskey="u" rel="up">HTML Xref</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Command-and-Variable-Index.html" title="Index" rel="index">Index</a>]</p>
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<span id="HTML-Cross_002dreference-Link-Basics"></span><h4 class="subsection">22.4.1 HTML Cross-reference Link Basics</h4>
<span id="index-HTML-cross_002dreference-link-basics"></span>
<p>For our purposes, an HTML link consists of four components: a host
name, a directory part, a file part, and a target part. We
always assume the <code>http</code> protocol. For example:
</p>
<div class="example">
<pre class="example">http://<var>host</var>/<var>dir</var>/<var>file</var>.html#<var>target</var>
</pre></div>
<p>The information to construct a link comes from the node name and
manual name in the cross-reference command in the Texinfo source
(see <a href="Cross-References.html">Cross References</a>), and from <em>external information</em>
(see <a href="HTML-Xref-Configuration.html">HTML Xref Configuration</a>).
</p>
<p>We now consider each part in turn.
</p>
<p>The <var>host</var> is hardwired to be the local host. This could either
be the literal string ‘<samp>localhost</samp>’, or, according to the rules for
HTML links, the ‘<samp>http://localhost/</samp>’ could be omitted entirely.
</p>
<p>The <var>dir</var> and <var>file</var> parts are more complicated, and depend on
the relative split/mono nature of both the manual being processed and
the manual that the cross-reference refers to. The underlying idea is
that there is one directory for Texinfo manuals in HTML, and a given
<var>manual</var> is either available as a monolithic file
<samp><var>manual</var>.html</samp>, or a split subdirectory
<samp><var>manual</var>/*.html</samp>. Here are the cases:
</p>
<ul>
<li> If the present manual is split, and the referent manual is also split,
the directory is ‘<samp>../<var>referent/</var></samp>’ and the file is the
expanded node name (described later).
</li><li> If the present manual is split, and the referent manual is mono, the
directory is ‘<samp>../</samp>’ and the file is <samp><var>referent</var>.html</samp>.
</li><li> If the present manual is mono, and the referent manual is split, the
directory is <samp><var>referent</var>/</samp> and the file is the expanded node
name.
</li><li> If the present manual is mono, and the referent manual is also mono,
the directory is <samp>./</samp> (or just the empty string), and the file is
<samp><var>referent</var>.html</samp>.
</li></ul>
<span id="index-BASEFILENAME_005fLENGTH-1"></span>
<p>Another rule, that only holds for filenames, is that base filenames
are truncated to 245 characters, to allow for an extension to be
appended and still comply with the 255-character limit which is common
to many filesystems. Although technically this can be changed with
the <code>BASEFILENAME_LENGTH</code> customization variable (see <a href="Other-Customization-Variables.html">Other Customization Variables</a>), doing so would make cross-manual references
to such nodes invalid.
</p>
<p>Any directory part in the filename argument of the source cross
reference command is ignored. Thus, <code>@xref{,,,../foo}</code> and
<code>@xref{,,,foo}</code> both use ‘<samp>foo</samp>’ as the manual name. This
is because any such attempted hardwiring of the directory is very
unlikely to be useful for both Info and HTML output.
</p>
<p>Finally, the <var>target</var> part is always the expanded node name.
</p>
<p>Whether the present manual is split or mono is determined by user
option; <code>makeinfo</code> defaults to split, with the
<samp>--no-split</samp> option overriding this.
</p>
<p>Whether the referent manual is split or mono, however, is another bit
of the external information (see <a href="HTML-Xref-Configuration.html">HTML Xref Configuration</a>). By
default, <code>makeinfo</code> uses the same form of the referent manual
as the present manual.
</p>
<p>Thus, there can be a mismatch between the format of the referent
manual that the generating software assumes, and the format it’s
actually present in. See <a href="HTML-Xref-Mismatch.html">HTML Xref Mismatch</a>.
</p>
<hr>
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<p>
Next: <a href="HTML-Xref-Node-Name-Expansion.html" accesskey="n" rel="next">HTML Xref Node Name Expansion</a>, Up: <a href="HTML-Xref.html" accesskey="u" rel="up">HTML Xref</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Command-and-Variable-Index.html" title="Index" rel="index">Index</a>]</p>
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