Server Side Includes

What are Server Side Includes and what can I do with them?

Server-side Includes will run on most, but not all servers. They were first introduced in the NCSA server; Apache has taken it a step farther with eXtended Server-side Includes. Unfortunately, they will not run on CERN.

An SSI is a command or directive placed in an HTML file through the use of a comment line. With a simple SSI command you can update an entire site design, dynamically add the current time and date or the date a file was last modified, execute shell and CGI scripts and more! A definite boon to web developers who are short on funds and time and over worked with a gazillion pages to manage.

How to enable

Includes can be "turned on" by editing either the server's configuration files or adding an .htaccess file to the directory you want to enable includes in.

• Server Configuration

  If you have access to your servers configuration files you can enable SSI with a small edit to the access.conf and srm.conf.

  Telnet into your server, navigating to the directory where your configuration files are located. This may be something like usr/local/etc/httpd/conf/. Using your favorite text editor, open srm.conf and locate the following lines:

  # If you want to use server side includes, or CGI outside
  # ScriptAliased directories, uncomment the following lines.
  
  #AddType text/x-server-parsed-html .shtml
  #AddType application/x-httpd-CGI .CGI
  

  You may or may not have the commented instruction lines, but what you're looking for are the two lines that start with AddType. You need to remove the # from in front of them.

  Save your changes and move on to access.conf. You'll need to locate the section of this file that deals with specifying which directory should be set as DocumentRoot. You will probably find something similar to the section below, although it may have other settings between the <Directory> and </Directory> tags.

  # This should be changed to whatever you set DocumentRoot to.
  
  <Directory /usr/local/etc/httpd/htdocs>
  
  # This may also be "None", "All", or any combination of "Indexes",
  # "Includes", or "FollowSymLinks"
  
  Options Indexes FollowSymLinks Includes
  
  </Directory>
  
  

  If you do not wish to allow scripts or shell commands to be run add IncludesNOEXEC to the options line. This will allow SSIs but not CGI or shell commands.

  Note: In the latest version Apache there is one file that contains all of the config stuff.. the httpd.conf. You can make all of the above edits in this one file.

• .htaccess

  If you don't have access to your server config files, all is not lost. Create a file with your favorite text editor, naming it .htaccess. (Yes, the (.) is important. It tells your server that this is a hidden file that can't be seen by the casual snoop). Add the following three lines to your .htaccess file.

  Options Indexes FollowSymLinks Includes
  AddType application/x-httpd-CGI .CGI
  AddType text/x-server-parsed-html .shtml	
  

  .htaccess should be uploaded to the directory you want to protect. All sub-directories inside that directory will also be protected. If you wish to exclude CGI or shell commands on a per directory basis you can add the IncludesNOEXEC to the options line in the .htaccess file.

  Why .shtml? Can't I use .html?

  A file that contains includes must be parsed by the server. This puts an extra load on the server but unless your site receives [millions] of visitors a day it's unlikely you'll notice a slow-down in load time. Still, if you're not using includes to add the headers and footers to your entire site there's really no need to parse every single page. If your plan is to just add a few includes to special pages, give them a file extension of .shtml and the server will parse only those pages. On the other hand, if you have an existing site of multiple pages, plan to use includes to add headers and footers and don't look forward to renaming all of your files to .shtml you can add the line
  

  AddType text/x-server-parsed-html .html
  to your .htaccess file instead. All of your pages will be parsed, but they'll need to be anyway to grab those headers/footers.

Contents:

SSI Syntax
The config directive
   Time/Date Formats
Includes
Printing Environment Variables with echo
CGI Environment Variables
CGI Environment Variables cont.
Printing page stats

SSI Syntax