13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg<?xml version='1.0' encoding='UTF-8' ?>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg<!DOCTYPE manualpage SYSTEM "/style/manualpage.dtd">

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg<?xml-stylesheet type="text/xsl" href="/style/manual.en.xsl"?>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg<manualpage>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg<relativepath href=".."/>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg<title>Apache Tutorial: Introduction to Server Side Includes</title>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg<summary>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg<p>Server-side includes provide a means to add dynamic content to

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankgexisting HTML documents.</p>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg</summary>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg<section id="related"><title>Introduction</title>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg <related>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg <modulelist>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg <module>mod_include</module>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg <module>mod_cgi</module>

16b55a35cff91315d261d1baa776138af465c4e4fuankg <module>mod_expires</module>

16b55a35cff91315d261d1baa776138af465c4e4fuankg </modulelist>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg <directivelist>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg <directive module="core">Options</directive>

16b55a35cff91315d261d1baa776138af465c4e4fuankg <directive module="mod_include">XBitHack</directive>

16b55a35cff91315d261d1baa776138af465c4e4fuankg <directive module="mod_mime">AddType</directive>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg <directive module="core">SetOutputFilter</directive>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg <directive module="mod_setenvif">BrowserMatchNoCase</directive>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg </directivelist>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg</related>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg <p>This article deals with Server Side Includes, usually called

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg simply SSI. In this article, I'll talk about configuring your

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg server to permit SSI, and introduce some basic SSI techniques

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg for adding dynamic content to your existing HTML pages.</p>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg <p>In the latter part of the article, we'll talk about some of

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg the somewhat more advanced things that can be done with SSI,

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg such as conditional statements in your SSI directives.</p>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg</section>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg<section id="what"><title>What are SSI?</title>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg <p>SSI (Server Side Includes) are directives that are placed in

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg HTML pages, and evaluated on the server while the pages are

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg being served. They let you add dynamically generated content to

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg an existing HTML page, without having to serve the entire page

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg via a CGI program, or other dynamic technology.</p>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg <p>The decision of when to use SSI, and when to have your page

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg entirely generated by some program, is usually a matter of how

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg much of the page is static, and how much needs to be

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg recalculated every time the page is served. SSI is a great way

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg to add small pieces of information, such as the current time.

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg But if a majority of your page is being generated at the time

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg that it is served, you need to look for some other

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg solution.</p>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg</section>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg<section id="configuring">

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg<title>Configuring your server to permit SSI</title>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg <p>To permit SSI on your server, you must have the following

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg directive either in your <code>httpd.conf</code> file, or in a

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg <code>.htaccess</code> file:</p>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg<example>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg Options +Includes

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg</example>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg <p>This tells Apache that you want to permit files to be parsed

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg for SSI directives. Note that most configurations contain

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg multiple <directive module="core">Options</directive> directives

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg that can override each other. You will probably need to apply the

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg <code>Options</code> to the specific directory where you want SSI

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg enabled in order to assure that it gets evaluated last.</p>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg <p>Not just any file is parsed for SSI directives. You have to

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg tell Apache which files should be parsed. There are two ways to

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg do this. You can tell Apache to parse any file with a

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg particular file extension, such as <code>.shtml</code>, with

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg the following directives:</p>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg<example>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg AddType text/html .shtml<br />

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg AddOutputFilter INCLUDES .shtml

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg</example>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg <p>One disadvantage to this approach is that if you wanted to

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg add SSI directives to an existing page, you would have to

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg change the name of that page, and all links to that page, in

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg order to give it a <code>.shtml</code> extension, so that those

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg directives would be executed.</p>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg <p>The other method is to use the <directive

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg module="mod_includes">XBitHack</directive> directive:</p>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg<example>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg XBitHack on

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg</example>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg <p><directive module="mod_includes">XBitHack</directive>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg tells Apache to parse files for SSI

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg directives if they have the execute bit set. So, to add SSI

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg directives to an existing page, rather than having to change

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg the file name, you would just need to make the file executable

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg using <code>chmod</code>.</p>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg<example>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg chmod +x pagename.html

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg</example>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg <p>A brief comment about what not to do. You'll occasionally

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg see people recommending that you just tell Apache to parse all

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg <code>.html</code> files for SSI, so that you don't have to

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg mess with <code>.shtml</code> file names. These folks have

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg perhaps not heard about <directive

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg module="mod_includes">XBitHack</directive>. The thing to

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg keep in mind is that, by doing this, you're requiring that

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg Apache read through every single file that it sends out to

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg clients, even if they don't contain any SSI directives. This

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg can slow things down quite a bit, and is not a good idea.</p>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg <p>Of course, on Windows, there is no such thing as an execute

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg bit to set, so that limits your options a little.</p>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg <p>In its default configuration, Apache does not send the last

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg modified date or content length HTTP headers on SSI pages,

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg because these values are difficult to calculate for dynamic

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg content. This can prevent your document from being cached, and

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg result in slower perceived client performance. There are two

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg ways to solve this:</p>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg <ol>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg <li>Use the <code>XBitHack Full</code> configuration. This

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg tells Apache to determine the last modified date by looking

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg only at the date of the originally requested file, ignoring

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg the modification date of any included files.</li>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg <li>Use the directives provided by

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg <module>mod_expires</module> to set an explicit expiration

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg time on your files, thereby letting browsers and proxies

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg know that it is acceptable to cache them.</li>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg </ol>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg</section>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg<section id="basic"><title>Basic SSI directives</title>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg <p>SSI directives have the following syntax:</p>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg<example>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg &lt;!--#element attribute=value attribute=value ... --&gt;

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg</example>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg <p>It is formatted like an HTML comment, so if you don't have

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg SSI correctly enabled, the browser will ignore it, but it will

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg still be visible in the HTML source. If you have SSI correctly

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg configured, the directive will be replaced with its

de9fd9ad794deaf3ec7b8b5efa0fdd6950b1644bfuankg results.</p>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg <p>The element can be one of a number of things, and we'll talk

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg some more about most of these in the next installment of this

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg series. For now, here are some examples of what you can do with

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg SSI</p>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg<section id="todaysdate"><title>Today's date</title>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg<example>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg &lt;!--#echo var="DATE_LOCAL" --&gt;

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg</example>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg <p>The <code>echo</code> element just spits out the value of a

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg variable. There are a number of standard variables, which

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg include the whole set of environment variables that are

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg available to CGI programs. Also, you can define your own

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg variables with the <code>set</code> element.</p>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg <p>If you don't like the format in which the date gets printed,

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg you can use the <code>config</code> element, with a

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg <code>timefmt</code> attribute, to modify that formatting.</p>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg<example>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg &lt;!--#config timefmt="%A %B %d, %Y" --&gt;<br />

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg Today is &lt;!--#echo var="DATE_LOCAL" --&gt;

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg</example>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg</section>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg<section id="lastmodified"><title>Modification date of the file</title>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg<example>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg This document last modified &lt;!--#flastmod file="index.html" --&gt;

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg</example>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg <p>This element is also subject to <code>timefmt</code> format

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg configurations.</p>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg</section>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg<section id="cgi"><title>Including the results of a CGI program</title>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg <p>This is one of the more common uses of SSI - to output the

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg results of a CGI program, such as everybody's favorite, a ``hit

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg counter.''</p>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg<example>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg &lt;!--#include virtual="/cgi-bin/counter.pl" --&gt;

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg</example>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg</section>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg</section>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg<section id="additionalexamples">

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg<title>Additional examples</title>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg <p>Following are some specific examples of things you can do in

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg your HTML documents with SSI.</p>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg <hr />

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg<section id="docmodified"><title>When was this document

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankgmodified?</title>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg <p>Earlier, we mentioned that you could use SSI to inform the

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg user when the document was most recently modified. However, the

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg actual method for doing that was left somewhat in question. The

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg following code, placed in your HTML document, will put such a

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg time stamp on your page. Of course, you will have to have SSI

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg correctly enabled, as discussed above.</p>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg<example>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg &lt;!--#config timefmt="%A %B %d, %Y" --&gt;<br />

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg This file last modified &lt;!--#flastmod file="ssi.shtml" --&gt;

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg</example>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg <p>Of course, you will need to replace the

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg <code>ssi.shtml</code> with the actual name of the file that

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg you're referring to. This can be inconvenient if you're just

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg looking for a generic piece of code that you can paste into any

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg file, so you probably want to use the

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg <code>LAST_MODIFIED</code> variable instead:</p>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg<example>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg &lt;!--#config timefmt="%D" --&gt;<br />

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg This file last modified &lt;!--#echo var="LAST_MODIFIED" --&gt;

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg</example>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg <p>For more details on the <code>timefmt</code> format, go to

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg your favorite search site and look for <code>strftime</code>. The

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg syntax is the same.</p>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg</section>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg<section id="footer">

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg<title>Including a standard footer</title>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg <p>If you are managing any site that is more than a few pages,

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg you may find that making changes to all those pages can be a

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg real pain, particularly if you are trying to maintain some kind

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg of standard look across all those pages.</p>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg <p>Using an include file for a header and/or a footer can

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg reduce the burden of these updates. You just have to make one

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg footer file, and then include it into each page with the

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg <code>include</code> SSI command. The <code>include</code>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg element can determine what file to include with either the

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg <code>file</code> attribute, or the <code>virtual</code>

13b501825bce68e7e49b4bc775da93e38d9bd9f3fuankg 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>

<example>

&lt;!--#include virtual="/footer.html" --&gt;

</example>

<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>

</section>

</section>

<section id="config">

<title>What else can I config?</title>

<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>

<example>

[an error occurred while processing this directive]

</example>

<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>

<example>

&lt;!--#config errmsg="[It appears that you don't know how to use SSI]" --&gt;

</example>

<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>

</section>

<section id="exec">

<title>Executing commands</title>

<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>

<example>

&lt;pre&gt;<br />

&lt;!--#exec cmd="ls" --&gt;<br />

&lt;/pre&gt;

</example>

<p>or, on Windows</p>

<example>

&lt;pre&gt;<br />

&lt;!--#exec cmd="dir" --&gt;<br />

&lt;/pre&gt;

</example>

<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>

</section>

<section id="advanced">

<title>Advanced SSI techniques</title>

<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>

<section id="caveat"><title>Caveat</title>

<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>

</section>

<section id="variables"><title>Setting variables</title>

<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>

<example>

&lt;!--#set var="name" value="Rich" --&gt;

</example>

<p>In addition to merely setting values literally like that,

you can use any other variable, including, for example,

environment variables, or some of the variables we discussed in

the last article (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>

<example>

&lt;!--#set var="modified" value="$LAST_MODIFIED" --&gt;

</example>

<p>To put a literal dollar sign into the value of your

variable, you need to escape the dollar sign with a

backslash.</p>

<example>

&lt;!--#set var="cost" value="\$100" --&gt;

</example>

<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>

<example>

&lt;!--#set var="date" value="${DATE_LOCAL}_${DATE_GMT}" --&gt;

</example>

</section>

<section id="conditional">

<title>Conditional expressions</title>

<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.

<module>mod_include</module> 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>

<example>

&lt;!--#if expr="test_condition" --&gt;<br />

&lt;!--#elif expr="test_condition" --&gt;<br />

&lt;!--#else --&gt;<br />

&lt;!--#endif --&gt;

</example>

<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 <module>mod_include</module>

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>

<example>

BrowserMatchNoCase macintosh Mac<br />

BrowserMatchNoCase MSIE InternetExplorer

</example>

<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>

<example>

&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;

</example>

<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>

</section>

</section>

<section id="conclusion"><title>Conclusion</title>

<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>

</section>

</manualpage>