SSI

With hundreds or more pages, you will want to separate out code that is common to all pages.

SSI is one way of doing this. But far from the only way.

SSI (Server Side Include)
Apache docs
Include common code (e.g. header and footer) on every page.
Include a line like:
```

```
Can change header.html and it changes in all pages.
I use SSI on these notes.

SSI is invisible to client

If you include CSS:
```
<link rel=stylesheet type="text/css" href="file.css">
```
or JavaScript:
```
<script src=file.js ></script>
```
the user (client-side) can see the include has happened.
With SSI, the client-side can't detect the include has happened. It just gets a load of HTML in the page. It might be hard-coded in each page. The client can't tell.

SSI is enabled for .shtml files on student.computing.dcu.ie
ssh to student.computing.dcu.ie and see the Apache web server configuration files:
/etc/apache2/*.conf

Make a file.shtml in your web directory:
```
cd
cd public_html
gedit file.shtml &
```
Insert an SSI line in the file to get it to include another html file.
Test it works. Look at:
https://student.computing.dcu.ie/~username/file.shtml
and see that it is including the other file.

One useful one is to echo environment variables that exist on the server.

 <script src="header.js" ></script>

where header.js does:

 document.write ( bunch of HTML );