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+<?xml version="1.0" encoding="ISO-8859-1"?>
+<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
+<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en"><head><!--
+ XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
+ This file is generated from xml source: DO NOT EDIT
+ XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
+ -->
+<title>Apache Tutorial: Introduction to Server Side Includes - Apache HTTP Server</title>
+<link href="../style/css/manual.css" rel="stylesheet" media="all" type="text/css" title="Main stylesheet" />
+<link href="../style/css/manual-loose-100pc.css" rel="alternate stylesheet" media="all" type="text/css" title="No Sidebar - Default font size" />
+<link href="../style/css/manual-print.css" rel="stylesheet" media="print" type="text/css" />
+<link href="../images/favicon.ico" rel="shortcut icon" /></head>
+<body id="manual-page"><div id="page-header">
+<p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="../faq/">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p>
+<p class="apache">Apache HTTP Server Version 2.0</p>
+<img alt="" src="../images/feather.gif" /></div>
+<div class="up"><a href="./"><img title="&lt;-" alt="&lt;-" src="../images/left.gif" /></a></div>
+<div id="path">
+<a href="http://www.apache.org/">Apache</a> &gt; <a href="http://httpd.apache.org/">HTTP Server</a> &gt; <a href="http://httpd.apache.org/docs/">Documentation</a> &gt; <a href="../">Version 2.0</a> &gt; <a href="./">How-To / Tutorials</a></div><div id="page-content"><div id="preamble"><h1>Apache Tutorial: Introduction to Server Side Includes</h1>
+<div class="toplang">
+<p><span>Available Languages: </span><a href="../en/howto/ssi.html" title="English">&nbsp;en&nbsp;</a> |
+<a href="../ja/howto/ssi.html" hreflang="ja" rel="alternate" title="Japanese">&nbsp;ja&nbsp;</a> |
+<a href="../ko/howto/ssi.html" hreflang="ko" rel="alternate" title="Korean">&nbsp;ko&nbsp;</a></p>
+</div>
+
+<p>Server-side includes provide a means to add dynamic content to
+existing HTML documents.</p>
+</div>
+<div id="quickview"><ul id="toc"><li><img alt="" src="../images/down.gif" /> <a href="#related">Introduction</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#what">What are SSI?</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#configuring">Configuring your server to permit SSI</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#basic">Basic SSI directives</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#additionalexamples">Additional examples</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#config">What else can I config?</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#exec">Executing commands</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#advanced">Advanced SSI techniques</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#conclusion">Conclusion</a></li>
+</ul></div>
+<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="related" id="related">Introduction</a></h2>
+ <table class="related"><tr><th>Related Modules</th><th>Related Directives</th></tr><tr><td><ul><li><code class="module"><a href="../mod/mod_include.html">mod_include</a></code></li><li><code class="module"><a href="../mod/mod_cgi.html">mod_cgi</a></code></li><li><code class="module"><a href="../mod/mod_expires.html">mod_expires</a></code></li></ul></td><td><ul><li><code class="directive"><a href="../mod/core.html#options">Options</a></code></li><li><code class="directive"><a href="../mod/mod_include.html#xbithack">XBitHack</a></code></li><li><code class="directive"><a href="../mod/mod_mime.html#addtype">AddType</a></code></li><li><code class="directive"><a href="../mod/core.html#setoutputfilter">SetOutputFilter</a></code></li><li><code class="directive"><a href="../mod/mod_setenvif.html#browsermatchnocase">BrowserMatchNoCase</a></code></li></ul></td></tr></table>
+
+ <p>This article deals with Server Side Includes, usually called
+ simply SSI. In this article, I'll talk about configuring your
+ server to permit SSI, and introduce some basic SSI techniques
+ for adding dynamic content to your existing HTML pages.</p>
+
+ <p>In the latter part of the article, we'll talk about some of
+ the somewhat more advanced things that can be done with SSI,
+ such as conditional statements in your SSI directives.</p>
+
+</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="what" id="what">What are SSI?</a></h2>
+
+ <p>SSI (Server Side Includes) are directives that are placed in
+ HTML pages, and evaluated on the server while the pages are
+ being served. They let you add dynamically generated content to
+ an existing HTML page, without having to serve the entire page
+ via a CGI program, or other dynamic technology.</p>
+
+ <p>The decision of when to use SSI, and when to have your page
+ entirely generated by some program, is usually a matter of how
+ much of the page is static, and how much needs to be
+ recalculated every time the page is served. SSI is a great way
+ to add small pieces of information, such as the current time.
+ But if a majority of your page is being generated at the time
+ that it is served, you need to look for some other
+ solution.</p>
+</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="configuring" id="configuring">Configuring your server to permit SSI</a></h2>
+
+
+ <p>To permit SSI on your server, you must have the following
+ directive either in your <code>httpd.conf</code> file, or in a
+ <code>.htaccess</code> file:</p>
+<div class="example"><p><code>
+ Options +Includes
+</code></p></div>
+
+ <p>This tells Apache that you want to permit files to be parsed
+ for SSI directives. Note that most configurations contain
+ multiple <code class="directive"><a href="../mod/core.html#options">Options</a></code> directives
+ that can override each other. You will probably need to apply the
+ <code>Options</code> to the specific directory where you want SSI
+ enabled in order to assure that it gets evaluated last.</p>
+
+ <p>Not just any file is parsed for SSI directives. You have to
+ tell Apache which files should be parsed. There are two ways to
+ do this. You can tell Apache to parse any file with a
+ particular file extension, such as <code>.shtml</code>, with
+ the following directives:</p>
+<div class="example"><p><code>
+ AddType text/html .shtml<br />
+ AddOutputFilter INCLUDES .shtml
+</code></p></div>
+
+ <p>One disadvantage to this approach is that if you wanted to
+ add SSI directives to an existing page, you would have to
+ change the name of that page, and all links to that page, in
+ order to give it a <code>.shtml</code> extension, so that those
+ directives would be executed.</p>
+
+ <p>The other method is to use the <code class="directive"><a href="../mod/mod_include.html#xbithack">XBitHack</a></code> directive:</p>
+<div class="example"><p><code>
+ XBitHack on
+</code></p></div>
+
+ <p><code class="directive"><a href="../mod/mod_include.html#xbithack">XBitHack</a></code>
+ tells Apache to parse files for SSI
+ directives if they have the execute bit set. So, to add SSI
+ directives to an existing page, rather than having to change
+ the file name, you would just need to make the file executable
+ using <code>chmod</code>.</p>
+<div class="example"><p><code>
+ chmod +x pagename.html
+</code></p></div>
+
+ <p>A brief comment about what not to do. You'll occasionally
+ see people recommending that you just tell Apache to parse all
+ <code>.html</code> files for SSI, so that you don't have to
+ mess with <code>.shtml</code> file names. These folks have
+ perhaps not heard about <code class="directive"><a href="../mod/mod_include.html#xbithack">XBitHack</a></code>. The thing to
+ keep in mind is that, by doing this, you're requiring that
+ Apache read through every single file that it sends out to
+ clients, even if they don't contain any SSI directives. This
+ can slow things down quite a bit, and is not a good idea.</p>
+
+ <p>Of course, on Windows, there is no such thing as an execute
+ bit to set, so that limits your options a little.</p>
+
+ <p>In its default configuration, Apache does not send the last
+ modified date or content length HTTP headers on SSI pages,
+ because these values are difficult to calculate for dynamic
+ content. This can prevent your document from being cached, and
+ result in slower perceived client performance. There are two
+ ways to solve this:</p>
+
+ <ol>
+ <li>Use the <code>XBitHack Full</code> configuration. This
+ tells Apache to determine the last modified date by looking
+ only at the date of the originally requested file, ignoring
+ the modification date of any included files.</li>
+
+ <li>Use the directives provided by
+ <code class="module"><a href="../mod/mod_expires.html">mod_expires</a></code> to set an explicit expiration
+ time on your files, thereby letting browsers and proxies
+ know that it is acceptable to cache them.</li>
+ </ol>
+</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="basic" id="basic">Basic SSI directives</a></h2>
+
+ <p>SSI directives have the following syntax:</p>
+<div class="example"><p><code>
+ &lt;!--#element attribute=value attribute=value ... --&gt;
+</code></p></div>
+
+ <p>It is formatted like an HTML comment, so if you don't have
+ SSI correctly enabled, the browser will ignore it, but it will
+ still be visible in the HTML source. If you have SSI correctly
+ configured, the directive will be replaced with its
+ results.</p>
+
+ <p>The element can be one of a number of things, and we'll talk
+ some more about most of these in the next installment of this
+ series. For now, here are some examples of what you can do with
+ SSI</p>
+
+<h3><a name="todaysdate" id="todaysdate">Today's date</a></h3>
+
+<div class="example"><p><code>
+ &lt;!--#echo var="DATE_LOCAL" --&gt;
+</code></p></div>
+
+ <p>The <code>echo</code> element just spits out the value of a
+ variable. There are a number of standard variables, which
+ include the whole set of environment variables that are
+ available to CGI programs. Also, you can define your own
+ variables with the <code>set</code> element.</p>
+
+ <p>If you don't like the format in which the date gets printed,
+ you can use the <code>config</code> element, with a
+ <code>timefmt</code> attribute, to modify that formatting.</p>
+
+<div class="example"><p><code>
+ &lt;!--#config timefmt="%A %B %d, %Y" --&gt;<br />
+ Today is &lt;!--#echo var="DATE_LOCAL" --&gt;
+</code></p></div>
+
+
+<h3><a name="lastmodified" id="lastmodified">Modification date of the file</a></h3>
+
+<div class="example"><p><code>
+ This document last modified &lt;!--#flastmod file="index.html" --&gt;
+</code></p></div>
+
+ <p>This element is also subject to <code>timefmt</code> format
+ configurations.</p>
+
+
+<h3><a name="cgi" id="cgi">Including the results of a CGI program</a></h3>
+
+ <p>This is one of the more common uses of SSI - to output the
+ results of a CGI program, such as everybody's favorite, a ``hit
+ counter.''</p>
+
+<div class="example"><p><code>
+ &lt;!--#include virtual="/cgi-bin/counter.pl" --&gt;
+</code></p></div>
+
+
+</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="additionalexamples" id="additionalexamples">Additional examples</a></h2>
+
+
+ <p>Following are some specific examples of things you can do in
+ your HTML documents with SSI.</p>
+
+<h3><a name="docmodified" id="docmodified">When was this document
+modified?</a></h3>
+
+ <p>Earlier, we mentioned that you could use SSI to inform the
+ user when the document was most recently modified. However, the
+ actual method for doing that was left somewhat in question. The
+ following code, placed in your HTML document, will put such a
+ time stamp on your page. Of course, you will have to have SSI
+ correctly enabled, as discussed above.</p>
+<div class="example"><p><code>
+ &lt;!--#config timefmt="%A %B %d, %Y" --&gt;<br />
+ This file last modified &lt;!--#flastmod file="ssi.shtml" --&gt;
+</code></p></div>
+
+ <p>Of course, you will need to replace the
+ <code>ssi.shtml</code> with the actual name of the file that
+ you're referring to. This can be inconvenient if you're just
+ looking for a generic piece of code that you can paste into any
+ file, so you probably want to use the
+ <code>LAST_MODIFIED</code> variable instead:</p>
+<div class="example"><p><code>
+ &lt;!--#config timefmt="%D" --&gt;<br />
+ This file last modified &lt;!--#echo var="LAST_MODIFIED" --&gt;
+</code></p></div>
+
+ <p>For more details on the <code>timefmt</code> format, go to
+ your favorite search site and look for <code>strftime</code>. The
+ syntax is the same.</p>
+
+
+<h3><a name="standard-footer" id="standard-footer">Including a standard footer</a></h3>
+
+
+ <p>If you are managing any site that is more than a few pages,
+ you may find that making changes to all those pages can be a
+ real pain, particularly if you are trying to maintain some kind
+ of standard look across all those pages.</p>
+
+ <p>Using an include file for a header and/or a footer can
+ reduce the burden of these updates. You just have to make one
+ footer file, and then include it into each page with the
+ <code>include</code> SSI command. The <code>include</code>
+ element can determine what file to include with either the
+ <code>file</code> attribute, or the <code>virtual</code>
+ attribute. The <code>file</code> attribute is a file path,
+ <em>relative to the current directory</em>. That means that it
+ cannot be an absolute file path (starting with /), nor can it
+ contain ../ as part of that path. The <code>virtual</code>
+ attribute is probably more useful, and should specify a URL
+ relative to the document being served. It can start with a /,
+ but must be on the same server as the file being served.</p>
+<div class="example"><p><code>
+ &lt;!--#include virtual="/footer.html" --&gt;
+</code></p></div>
+
+ <p>I'll frequently combine the last two things, putting a
+ <code>LAST_MODIFIED</code> directive inside a footer file to be
+ included. SSI directives can be contained in the included file,
+ and includes can be nested - that is, the included file can
+ include another file, and so on.</p>
+
+
+</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="config" id="config">What else can I config?</a></h2>
+
+
+ <p>In addition to being able to <code>config</code> the time
+ format, you can also <code>config</code> two other things.</p>
+
+ <p>Usually, when something goes wrong with your SSI directive,
+ you get the message</p>
+<div class="example"><p><code>
+ [an error occurred while processing this directive]
+</code></p></div>
+
+ <p>If you want to change that message to something else, you
+ can do so with the <code>errmsg</code> attribute to the
+ <code>config</code> element:</p>
+<div class="example"><p><code>
+ &lt;!--#config errmsg="[It appears that you don't know how to use SSI]" --&gt;
+</code></p></div>
+
+ <p>Hopefully, end users will never see this message, because
+ you will have resolved all the problems with your SSI
+ directives before your site goes live. (Right?)</p>
+
+ <p>And you can <code>config</code> the format in which file
+ sizes are returned with the <code>sizefmt</code> attribute. You
+ can specify <code>bytes</code> for a full count in bytes, or
+ <code>abbrev</code> for an abbreviated number in Kb or Mb, as
+ appropriate.</p>
+ </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="exec" id="exec">Executing commands</a></h2>
+
+
+ <p>I expect that I'll have an article some time in the coming
+ months about using SSI with small CGI programs. For now, here's
+ something else that you can do with the <code>exec</code>
+ element. You can actually have SSI execute a command using the
+ shell (<code>/bin/sh</code>, to be precise - or the DOS shell,
+ if you're on Win32). The following, for example, will give you
+ a directory listing.</p>
+<div class="example"><p><code>
+ &lt;pre&gt;<br />
+ &lt;!--#exec cmd="ls" --&gt;<br />
+ &lt;/pre&gt;
+</code></p></div>
+
+ <p>or, on Windows</p>
+<div class="example"><p><code>
+ &lt;pre&gt;<br />
+ &lt;!--#exec cmd="dir" --&gt;<br />
+ &lt;/pre&gt;
+</code></p></div>
+
+ <p>You might notice some strange formatting with this directive
+ on Windows, because the output from <code>dir</code> contains
+ the string ``&lt;<code>dir</code>&gt;'' in it, which confuses
+ browsers.</p>
+
+ <p>Note that this feature is exceedingly dangerous, as it will
+ execute whatever code happens to be embedded in the
+ <code>exec</code> tag. If you have any situation where users
+ can edit content on your web pages, such as with a
+ ``guestbook'', for example, make sure that you have this
+ feature disabled. You can allow SSI, but not the
+ <code>exec</code> feature, with the <code>IncludesNOEXEC</code>
+ argument to the <code>Options</code> directive.</p>
+ </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="advanced" id="advanced">Advanced SSI techniques</a></h2>
+
+
+ <p>In addition to spitting out content, Apache SSI gives you
+ the option of setting variables, and using those variables in
+ comparisons and conditionals.</p>
+
+<h3><a name="caveat" id="caveat">Caveat</a></h3>
+
+ <p>Most of the features discussed in this article are only
+ available to you if you are running Apache 1.2 or later. Of
+ course, if you are not running Apache 1.2 or later, you need to
+ upgrade immediately, if not sooner. Go on. Do it now. We'll
+ wait.</p>
+
+
+<h3><a name="variables" id="variables">Setting variables</a></h3>
+
+ <p>Using the <code>set</code> directive, you can set variables
+ for later use. We'll need this later in the discussion, so
+ we'll talk about it here. The syntax of this is as follows:</p>
+<div class="example"><p><code>
+ &lt;!--#set var="name" value="Rich" --&gt;
+</code></p></div>
+
+ <p>In addition to merely setting values literally like that, you
+ can use any other variable, including <a href="../env.html">environment variables</a> or the variables
+ discussed above (like <code>LAST_MODIFIED</code>, for example) to
+ give values to your variables. You will specify that something is
+ a variable, rather than a literal string, by using the dollar sign
+ ($) before the name of the variable.</p>
+
+ <div class="example"><p><code> &lt;!--#set var="modified" value="$LAST_MODIFIED" --&gt;
+ </code></p></div>
+
+ <p>To put a literal dollar sign into the value of your
+ variable, you need to escape the dollar sign with a
+ backslash.</p>
+<div class="example"><p><code>
+ &lt;!--#set var="cost" value="\$100" --&gt;
+</code></p></div>
+
+ <p>Finally, if you want to put a variable in the midst of a
+ longer string, and there's a chance that the name of the
+ variable will run up against some other characters, and thus be
+ confused with those characters, you can place the name of the
+ variable in braces, to remove this confusion. (It's hard to
+ come up with a really good example of this, but hopefully
+ you'll get the point.)</p>
+<div class="example"><p><code>
+ &lt;!--#set var="date" value="${DATE_LOCAL}_${DATE_GMT}" --&gt;
+</code></p></div>
+
+
+<h3><a name="conditional" id="conditional">Conditional expressions</a></h3>
+
+
+ <p>Now that we have variables, and are able to set and compare
+ their values, we can use them to express conditionals. This
+ lets SSI be a tiny programming language of sorts.
+ <code class="module"><a href="../mod/mod_include.html">mod_include</a></code> provides an <code>if</code>,
+ <code>elif</code>, <code>else</code>, <code>endif</code>
+ structure for building conditional statements. This allows you
+ to effectively generate multiple logical pages out of one
+ actual page.</p>
+
+ <p>The structure of this conditional construct is:</p>
+<div class="example"><p><code>
+ &lt;!--#if expr="test_condition" --&gt;<br />
+ &lt;!--#elif expr="test_condition" --&gt;<br />
+ &lt;!--#else --&gt;<br />
+ &lt;!--#endif --&gt;
+</code></p></div>
+
+ <p>A <em>test_condition</em> can be any sort of logical
+ comparison - either comparing values to one another, or testing
+ the ``truth'' of a particular value. (A given string is true if
+ it is nonempty.) For a full list of the comparison operators
+ available to you, see the <code class="module"><a href="../mod/mod_include.html">mod_include</a></code>
+ documentation. Here are some examples of how one might use this
+ construct.</p>
+
+ <p>In your configuration file, you could put the following
+ line:</p>
+<div class="example"><p><code>
+ BrowserMatchNoCase macintosh Mac<br />
+ BrowserMatchNoCase MSIE InternetExplorer
+</code></p></div>
+
+ <p>This will set environment variables ``Mac'' and
+ ``InternetExplorer'' to true, if the client is running Internet
+ Explorer on a Macintosh.</p>
+
+ <p>Then, in your SSI-enabled document, you might do the
+ following:</p>
+<div class="example"><p><code>
+ &lt;!--#if expr="${Mac} &amp;&amp; ${InternetExplorer}" --&gt;<br />
+ Apologetic text goes here<br />
+ &lt;!--#else --&gt;<br />
+ Cool JavaScript code goes here<br />
+ &lt;!--#endif --&gt;
+</code></p></div>
+
+ <p>Not that I have anything against IE on Macs - I just
+ struggled for a few hours last week trying to get some
+ JavaScript working on IE on a Mac, when it was working
+ everywhere else. The above was the interim workaround.</p>
+
+ <p>Any other variable (either ones that you define, or normal
+ environment variables) can be used in conditional statements.
+ With Apache's ability to set environment variables with the
+ <code>SetEnvIf</code> directives, and other related directives,
+ this functionality can let you do some pretty involved dynamic
+ stuff without ever resorting to CGI.</p>
+
+</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="conclusion" id="conclusion">Conclusion</a></h2>
+
+ <p>SSI is certainly not a replacement for CGI, or other
+ technologies used for generating dynamic web pages. But it is a
+ great way to add small amounts of dynamic content to pages,
+ without doing a lot of extra work.</p>
+</div></div>
+<div class="bottomlang">
+<p><span>Available Languages: </span><a href="../en/howto/ssi.html" title="English">&nbsp;en&nbsp;</a> |
+<a href="../ja/howto/ssi.html" hreflang="ja" rel="alternate" title="Japanese">&nbsp;ja&nbsp;</a> |
+<a href="../ko/howto/ssi.html" hreflang="ko" rel="alternate" title="Korean">&nbsp;ko&nbsp;</a></p>
+</div><div id="footer">
+<p class="apache">Copyright 2009 The Apache Software Foundation.<br />Licensed under the <a href="http://www.apache.org/licenses/LICENSE-2.0">Apache License, Version 2.0</a>.</p>
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