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| author | (no author) <(no author)@unknown> | 2002-03-18 03:09:33 +0000 |
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| committer | (no author) <(no author)@unknown> | 2002-03-18 03:09:33 +0000 |
| commit | fc08fc78d7beb04687e3d4929207b31e1705c6e8 (patch) | |
| tree | 50626f671b637981b07f222b7f8a2d3057b267c3 /docs/manual/howto/ssi.html.en | |
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| download | httpd-fc08fc78d7beb04687e3d4929207b31e1705c6e8.tar.gz | |
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diff --git a/docs/manual/howto/ssi.html.en b/docs/manual/howto/ssi.html.en deleted file mode 100644 index eef2ed2f9f..0000000000 --- a/docs/manual/howto/ssi.html.en +++ /dev/null @@ -1,548 +0,0 @@ -<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" - "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> - -<html xmlns="http://www.w3.org/1999/xhtml"> - <head> - <meta name="generator" content="HTML Tidy, see www.w3.org" /> - - <title>Apache Tutorial: Introduction to Server Side - Includes</title> - <link rev="made" href="mailto:rbowen@rcbowen.com" /> - </head> - <!-- Background white, links blue (unvisited), navy (visited), red (active) --> - - <body bgcolor="#FFFFFF" text="#000000" link="#0000FF" - vlink="#000080" alink="#FF0000"> - <!--#include virtual="header.html" --> - - <h1 align="CENTER">Apache Tutorial: Introduction to Server Side - Includes</h1> - <a id="__index__" name="__index__"></a> <!-- INDEX BEGIN --> - - - <ul> - <li><a - href="#apachetutorial:introductiontoserversideincludes">Apache - Tutorial: Introduction to Server Side Includes</a></li> - - <li><a href="#whataressi">What are SSI?</a></li> - - <li><a href="#configuringyourservertopermitssi">Configuring - your server to permit SSI</a></li> - - <li> - <a href="#basicssidirectives">Basic SSI directives</a> - - <ul> - <li><a href="#today'sdate">Today's date</a></li> - - <li><a href="#modificationdateofthefile">Modification - date of the file</a></li> - - <li><a href="#includingtheresultsofacgiprogram">Including - the results of a CGI program</a></li> - </ul> - </li> - - <li> - <a href="#additionalexamples">Additional examples</a> - - <ul> - <li><a href="#whenwasthisdocumentmodified">When was this - document modified?</a></li> - - <li><a href="#includingastandardfooter">Including a - standard footer</a></li> - - <li><a href="#whatelsecaniconfig">What else can I - config?</a></li> - - <li><a href="#executingcommands">Executing - commands</a></li> - </ul> - </li> - - <li> - <a href="#advancedssitechniques">Advanced SSI - techniques</a> - - <ul> - <li><a href="#settingvariables">Setting - variables</a></li> - - <li><a href="#conditionalexpressions">Conditional - expressions</a></li> - </ul> - </li> - - <li><a href="#conclusion">Conclusion</a></li> - </ul> - <!-- INDEX END --> - <hr /> - - <h2><a id="apachetutorial:introductiontoserversideincludes" - name="apachetutorial:introductiontoserversideincludes">Apache - Tutorial: Introduction to Server Side Includes</a></h2> - - <table border="1"> - <tr> - <td valign="top"><strong>Related Modules</strong><br /> - <br /> - <a href="../mod/mod_include.html">mod_include</a><br /> - <a href="../mod/mod_cgi.html">mod_cgi</a><br /> - <a href="../mod/mod_expires.html">mod_expires</a><br /> - </td> - - <td valign="top"><strong>Related Directives</strong><br /> - <br /> - <a href="../mod/core.html#options">Options</a><br /> - <a - href="../mod/mod_include.html#xbithack">XBitHack</a><br /> - <a href="../mod/mod_mime.html#addtype">AddType</a><br /> - <a - href="../mod/core.html.html#setoutputfilter">SetOutputFilter</a><br /> - <a - href="../mod/mod_setenvif.html#BrowserMatchNoCase">BrowserMatchNoCase</a><br /> - </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> - <hr /> - - <h2><a id="whataressi" name="whataressi">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> - <hr /> - - <h2><a id="configuringyourservertopermitssi" - name="configuringyourservertopermitssi">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> -<pre> - Options +Includes -</pre> - - <p>This tells Apache that you want to permit files to be parsed - for SSI directives. Note that most configurations contain - multiple <a href="../mod/core.html#options">Options</a> 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> -<pre> - AddType text/html .shtml - AddOutputFilter INCLUDES .shtml -</pre> - - <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>XBitHack</code> - directive:</p> -<pre> - XBitHack on -</pre> - - <p><code>XBitHack</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> -<pre> - chmod +x pagename.html -</pre> - - <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>XBitHack</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 <a - href="../mod/mod_expires.html">mod_expires</a> to set an - explicit expiration time on your files, thereby letting - browsers and proxies know that it is acceptable to cache - them.</li> - </ol> - <hr /> - - <h2><a id="basicssidirectives" name="basicssidirectives">Basic - SSI directives</a></h2> - - <p>SSI directives have the following syntax:</p> -<pre> - <!--#element attribute=value attribute=value ... --> -</pre> - - <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 id="today'sdate" name="today'sdate">Today's - date</a></h3> -<pre> - <!--#echo var="DATE_LOCAL" --> -</pre> - - <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> -<pre> - <!--#config timefmt="%A %B %d, %Y" --> - Today is <!--#echo var="DATE_LOCAL" --> -</pre> - - <h3><a id="modificationdateofthefile" - name="modificationdateofthefile">Modification date of the - file</a></h3> -<pre> - This document last modified <!--#flastmod file="index.html" --> -</pre> - - <p>This element is also subject to <code>timefmt</code> format - configurations.</p> - - <h3><a id="includingtheresultsofacgiprogram" - name="includingtheresultsofacgiprogram">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> -<pre> - <!--#include virtual="/cgi-bin/counter.pl" --> -</pre> - <hr /> - - <h2><a id="additionalexamples" - name="additionalexamples">Additional examples</a></h2> - - <p>Following are some specific examples of things you can do in - your HTML documents with SSI.</p> - <hr /> - - <h2><a id="whenwasthisdocumentmodified" - name="whenwasthisdocumentmodified">When was this document - modified?</a></h2> - - <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> -<pre> - <!--#config timefmt="%A %B %d, %Y" --> - This file last modified <!--#flastmod file="ssi.shtml" --> -</pre> - - <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> -<pre> - <!--#config timefmt="%D" --> - This file last modified <!--#echo var="LAST_MODIFIED" --> -</pre> - - <p>For more details on the <code>timefmt</code> format, go to - your favorite search site and look for <code>ctime</code>. The - syntax is the same.</p> - <hr /> - - <h2><a id="includingastandardfooter" - name="includingastandardfooter">Including a standard - footer</a></h2> - - <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> -<pre> - <!--#include virtual="/footer.html" --> -</pre> - - <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> - <hr /> - - <h2><a id="whatelsecaniconfig" name="whatelsecaniconfig">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> -<pre> - [an error occurred while processing this directive] -</pre> - - <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> -<pre> - <!--#config errmsg="[It appears that you don't know how to use SSI]" --> -</pre> - - <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> - <hr /> - - <h2><a id="executingcommands" - name="executingcommands">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> -<pre> - <pre> - <!--#exec cmd="ls" --> - </pre> -</pre> - - <p>or, on Windows</p> -<pre> - <pre> - <!--#exec cmd="dir" --> - </pre> -</pre> - - <p>You might notice some strange formatting with this directive - on Windows, because the output from <code>dir</code> contains - the string ``<<code>dir</code>>'' 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> - <hr /> - - <h2><a id="advancedssitechniques" - name="advancedssitechniques">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 id="caveat" name="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> - <hr /> - - <h2><a id="settingvariables" name="settingvariables">Setting - variables</a></h2> - - <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> -<pre> - <!--#set var="name" value="Rich" --> -</pre> - - <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 ($) before the name of the variable.</p> -<pre> - <!--#set var="modified" value="$LAST_MODIFIED" --> -</pre> - - <p>To put a literal dollar sign into the value of your - variable, you need to escape the dollar sign with a - backslash.</p> -<pre> - <!--#set var="cost" value="\$100" --> -</pre> - - <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> -<pre> - <!--#set var="date" value="${DATE_LOCAL}_${DATE_GMT}" --> -</pre> - <hr /> - - <h2><a id="conditionalexpressions" - name="conditionalexpressions">Conditional expressions</a></h2> - - <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>mod_include</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> -<pre> - <!--#if expr="test_condition" --> - <!--#elif expr="test_condition" --> - <!--#else --> - <!--#endif --> -</pre> - - <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>mod_include</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> -<pre> - BrowserMatchNoCase macintosh Mac - BrowserMatchNoCase MSIE InternetExplorer -</pre> - - <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> -<pre> - <!--#if expr="${Mac} && ${InternetExplorer}" --> - Apologetic text goes here - <!--#else --> - Cool JavaScript code goes here - <!--#endif --> -</pre> - - <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> - <hr /> - - <h2><a id="conclusion" name="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> - <!--#include virtual="footer.html" --> - </body> -</html> - |