bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor<?xml version='1.0' encoding='UTF-8' ?>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor<!DOCTYPE manualpage SYSTEM "/style/manualpage.dtd">

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor<?xml-stylesheet type="text/xsl" href="/style/manual.en.xsl"?>

0679f53d7ea85c2cbb4970366f592782d9e26f5flgentis

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor<manualpage metafile="ssi.xml.meta">

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor<parentdocument href="./">How-To / Tutorials</parentdocument>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor<title>Apache Tutorial: Introduction to Server Side Includes</title>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor<summary>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor<p>Server-side includes provide a means to add dynamic content to

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzorexisting HTML documents.</p>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor</summary>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor<section id="related"><title>Introduction</title>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor <related>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor <modulelist>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor <module>mod_include</module>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor <module>mod_cgi</module>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor <module>mod_expires</module>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor </modulelist>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor <directivelist>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor <directive module="core">Options</directive>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor <directive module="mod_include">XBitHack</directive>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor <directive module="mod_mime">AddType</directive>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor <directive module="core">SetOutputFilter</directive>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor <directive module="mod_setenvif">BrowserMatchNoCase</directive>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor </directivelist>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor</related>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor <p>This article deals with Server Side Includes, usually called

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor simply SSI. In this article, I'll talk about configuring your

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor server to permit SSI, and introduce some basic SSI techniques

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor for adding dynamic content to your existing HTML pages.</p>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor <p>In the latter part of the article, we'll talk about some of

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor the somewhat more advanced things that can be done with SSI,

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor such as conditional statements in your SSI directives.</p>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor</section>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor<section id="what"><title>What are SSI?</title>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor <p>SSI (Server Side Includes) are directives that are placed in

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor HTML pages, and evaluated on the server while the pages are

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor being served. They let you add dynamically generated content to

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor an existing HTML page, without having to serve the entire page

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor via a CGI program, or other dynamic technology.</p>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor <p>The decision of when to use SSI, and when to have your page

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor entirely generated by some program, is usually a matter of how

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor much of the page is static, and how much needs to be

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor recalculated every time the page is served. SSI is a great way

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor to add small pieces of information, such as the current time.

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor But if a majority of your page is being generated at the time

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor that it is served, you need to look for some other

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor solution.</p>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor</section>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor<section id="configuring">

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor<title>Configuring your server to permit SSI</title>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor <p>To permit SSI on your server, you must have the following

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor directive either in your <code>httpd.conf</code> file, or in a

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor <code>.htaccess</code> file:</p>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor<example>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor Options +Includes

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor</example>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor

0679f53d7ea85c2cbb4970366f592782d9e26f5flgentis <p>This tells Apache that you want to permit files to be parsed

0679f53d7ea85c2cbb4970366f592782d9e26f5flgentis for SSI directives. Note that most configurations contain

0679f53d7ea85c2cbb4970366f592782d9e26f5flgentis multiple <directive module="core">Options</directive> directives

0679f53d7ea85c2cbb4970366f592782d9e26f5flgentis that can override each other. You will probably need to apply the

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor <code>Options</code> to the specific directory where you want SSI

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor enabled in order to assure that it gets evaluated last.</p>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor <p>Not just any file is parsed for SSI directives. You have to

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor tell Apache which files should be parsed. There are two ways to

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor do this. You can tell Apache to parse any file with a

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor particular file extension, such as <code>.shtml</code>, with

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor the following directives:</p>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor<example>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor AddType text/html .shtml<br />

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor AddOutputFilter INCLUDES .shtml

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor</example>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor <p>One disadvantage to this approach is that if you wanted to

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor add SSI directives to an existing page, you would have to

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor change the name of that page, and all links to that page, in

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor order to give it a <code>.shtml</code> extension, so that those

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor directives would be executed.</p>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor <p>The other method is to use the <directive

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor module="mod_include">XBitHack</directive> directive:</p>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor<example>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor XBitHack on

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor</example>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor <p><directive module="mod_include">XBitHack</directive>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor tells Apache to parse files for SSI

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor directives if they have the execute bit set. So, to add SSI

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor directives to an existing page, rather than having to change

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor the file name, you would just need to make the file executable

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor using <code>chmod</code>.</p>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor<example>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor chmod +x pagename.html

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor</example>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor <p>A brief comment about what not to do. You'll occasionally

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor see people recommending that you just tell Apache to parse all

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor <code>.html</code> files for SSI, so that you don't have to

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor mess with <code>.shtml</code> file names. These folks have

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor perhaps not heard about <directive

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor module="mod_include">XBitHack</directive>. The thing to

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor keep in mind is that, by doing this, you're requiring that

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor Apache read through every single file that it sends out to

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor clients, even if they don't contain any SSI directives. This

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor can slow things down quite a bit, and is not a good idea.</p>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor <p>Of course, on Windows, there is no such thing as an execute

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor bit to set, so that limits your options a little.</p>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor <p>In its default configuration, Apache does not send the last

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor modified date or content length HTTP headers on SSI pages,

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor because these values are difficult to calculate for dynamic

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor content. This can prevent your document from being cached, and

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor result in slower perceived client performance. There are two

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor ways to solve this:</p>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor <ol>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor <li>Use the <code>XBitHack Full</code> configuration. This

1db884f97626adc6cdca05468e9aad3868879f56lgentis tells Apache to determine the last modified date by looking

1db884f97626adc6cdca05468e9aad3868879f56lgentis only at the date of the originally requested file, ignoring

1db884f97626adc6cdca05468e9aad3868879f56lgentis the modification date of any included files.</li>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor <li>Use the directives provided by

1db884f97626adc6cdca05468e9aad3868879f56lgentis <module>mod_expires</module> to set an explicit expiration

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor time on your files, thereby letting browsers and proxies

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor know that it is acceptable to cache them.</li>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor </ol>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor</section>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor<section id="basic"><title>Basic SSI directives</title>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor <p>SSI directives have the following syntax:</p>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor<example>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor &lt;!--#element attribute=value attribute=value ... --&gt;

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor</example>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor <p>It is formatted like an HTML comment, so if you don't have

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor SSI correctly enabled, the browser will ignore it, but it will

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor still be visible in the HTML source. If you have SSI correctly

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor configured, the directive will be replaced with its

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor results.</p>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor <p>The element can be one of a number of things, and we'll talk

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor some more about most of these in the next installment of this

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor series. For now, here are some examples of what you can do with

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor SSI</p>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor<section id="todaysdate"><title>Today's date</title>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor<example>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor &lt;!--#echo var="DATE_LOCAL" --&gt;

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor</example>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor <p>The <code>echo</code> element just spits out the value of a

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor variable. There are a number of standard variables, which

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor include the whole set of environment variables that are

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor available to CGI programs. Also, you can define your own

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor variables with the <code>set</code> element.</p>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor <p>If you don't like the format in which the date gets printed,

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor you can use the <code>config</code> element, with a

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor <code>timefmt</code> attribute, to modify that formatting.</p>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor<example>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor &lt;!--#config timefmt="%A %B %d, %Y" --&gt;<br />

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor Today is &lt;!--#echo var="DATE_LOCAL" --&gt;

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor</example>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor</section>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor<section id="lastmodified"><title>Modification date of the file</title>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor<example>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor This document last modified &lt;!--#flastmod file="index.html" --&gt;

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor</example>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor <p>This element is also subject to <code>timefmt</code> format

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor configurations.</p>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor</section>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor<section id="cgi"><title>Including the results of a CGI program</title>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor <p>This is one of the more common uses of SSI - to output the

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor results of a CGI program, such as everybody's favorite, a ``hit

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor counter.''</p>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor<example>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor &lt;!--#include virtual="/cgi-bin/counter.pl" --&gt;

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor</example>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor</section>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor</section>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor<section id="additionalexamples">

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor<title>Additional examples</title>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor <p>Following are some specific examples of things you can do in

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor your HTML documents with SSI.</p>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor<section id="docmodified"><title>When was this document

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzormodified?</title>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor <p>Earlier, we mentioned that you could use SSI to inform the

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor user when the document was most recently modified. However, the

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor actual method for doing that was left somewhat in question. The

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor following code, placed in your HTML document, will put such a

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor time stamp on your page. Of course, you will have to have SSI

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor correctly enabled, as discussed above.</p>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor<example>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor &lt;!--#config timefmt="%A %B %d, %Y" --&gt;<br />

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor This file last modified &lt;!--#flastmod file="ssi.shtml" --&gt;

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor</example>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor <p>Of course, you will need to replace the

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor <code>ssi.shtml</code> with the actual name of the file that

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor you're referring to. This can be inconvenient if you're just

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor looking for a generic piece of code that you can paste into any

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor file, so you probably want to use the

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor <code>LAST_MODIFIED</code> variable instead:</p>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor<example>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor &lt;!--#config timefmt="%D" --&gt;<br />

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor This file last modified &lt;!--#echo var="LAST_MODIFIED" --&gt;

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor</example>

bfdab5d58a717a6d1fa9c1170a2a3b8355213367gryzor

<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>

</section>

<section id="standard-footer">

<title>Including a standard footer</title>

<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>

<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>