GuidesApache Guide: Introduction to Server Side Includes

Apache Guide: Introduction to Server Side Includes




This is the first of three articles dealing 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.

This is the first of three articles dealing with Server Side Includes,
usually called simply SSI. In this article, Rich talks about configuring your
server to permit SSI and introduce some basic SSI techniques for adding dynamic
content to your existing HTML pages.

In the second article, we’ll talk about some of the somewhat more advanced
things you can do with SSI, and in the third week, we’ll look at the advanced
things that can be done with SSI, such as conditional statements in your SSI
directives.

What are SSI?

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.

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.

Configuring Your Server to
Permit SSI

To permit SSI on your server, you must have the following directive either
in your httpd.conf file or in a .htaccess file:

     Options +Includes

This tells Apache that you want to permit files to be parsed for SSI
directives.

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
.shtml, with the following directives:

        AddType text/html .shtml

        AddHandler server-parsed .shtml

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 .shtml
extension, so that those directives would be executed.

The other method is to use the XBitHack directive:

        XBitHack on

XBitHack 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 chmod.

        chmod +x pagename.html

A brief comment about what not to do. You’ll occasionally see people
recommending that you just tell Apache to parse all .html files
for SSI, so that you don’t have to mess with .shtml file names.
These folks have perhaps not heard about XBitHack. 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.

Of course, on Windows, there is no such thing as an execute bit to set, so
that limits your options a little if you’re running Apache on Windows.

Basic SSI Directives

SSI directives have the following syntax:

        

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