Server Side Includes

Server Side Includes (SSI) are a primitive scripting language. Since the advent of JSP, ASP, PHP and JavaScript, SSI scripting has faded away. It is still used to include files and to display the modification times of files.

Sections that will be covered in the exam have headings that look like this.

Special SSI Variables Available to the echo command

LAST_MODIFIED: Last modified on Thursday, 17-Jun-2021 14:46:55 EDT
Last modified on 
DOCUMENT_NAME: The document name is ssi.shtml
The document name is 
DOCUMENT_URI: The document URI is /~downeyt/webdev/ssi.shtml
The document URI is 
DATE_GMT: The GMT date is Tuesday, 29-Apr-2025 18:04:01 GMT
The GMT date is 
DATE_LOCAL: The local date is Tuesday, 29-Apr-2025 14:04:01 EDT
The local date is

All Environment Variables are also Available

HTTP_USER_AGENT: The user agent is Mozilla/5.0 AppleWebKit/537.36 (KHTML, like Gecko; compatible; ClaudeBot/1.0; +claudebot@anthropic.com)
The user agent is 
HTTP_HOST: The http host is users.cis.fiu.edu
The http host is 
SERVER_NAME: The server name is users.cis.fiu.edu
The server name is 
HTTP_ACCEPT: Http accept is */*
Http accept is 
HTTP_ACCEPT_LANGUAGE: Http accept language is (none)
Http accept language is

Including Files

Relative references are relative to the current directory. It is not possible to go up the directory tree. Absolute references start with / and are relative to the document root.

Relative references use the file attribute:

This is a line of text included from a file in this directory.
Absolute references use the virtual attribute:

Creating Local Variables

It is possible to create a local variable inside a file that uses SSI commands.

Set a variable: 
Echo a variable: The value of fiu is www.fiu.edu
The value of fiu is

Size and Last Modified of a file

Last Modified. Relative references are relative to the current directory. Absolute references are relative to the document root.: Relative reference: Last modified on 
Last modified on Friday, 19-Oct-2018 15:29:15 EDT

Absolute reference: Last modified on 
Last modified on Wednesday, 19-Dec-2018 15:47:33 EST

File Size Relative references are relative to the current directory. Absolute references are relative to the document root.: Relative reference: File size in K 
File size in K 63

Absolute reference: File size in K 
File size in K 3.3K

Change the format of the output

For a list of the time formatting codes, visit this site: http://internetconnection.net/support/tech-ssitime.html

Change the last modified date to m/d/y, the decimal number day of the year, and am/pm

Change the file size to bytes

Last Modified Relative references are relative to the current directory. Absolute references are relative to the document root.: Relative reference: Last modified on 
Last modified on Friday 10/19/18 (day 292) at 03:29:15 PM

Absolute reference: Last modified on 
Last modified on Wednesday 12/19/18 (day 353) at 03:47:33 PM

File Size Relative references are relative to the current directory. Absolute references are relative to the document root.: Relative reference: File size in bytes 
File size in bytes 63

Absolute reference: File size in bytes 
File size in bytes 3,414

Including the output of commands (carefully)

Include the output of a cgi script.
The cgi parameter is relative to the document root of the server.

Hello from test.cgi

Including the output of a Unix command.
The cmd parameter is an absolute file system path.


Using Conditional Statements

Since Apache 2.3.12, the syntax for SSI conditional statements has changed. The new syntax is buggy and needs to be updated. This page uses the old Apache 2.2.x syntax with the directive SSILegacyExprParser on.

It is possible to use an if statment with SSI files. The conditional directives are if, elif, else, endif. It is also possible to do pattern matching using /pattern/. Here is an example that tests if this file was last modified on a weekday

Test if it was modified on a weekday

<!--#if expr="${LAST_MODIFIED} = /Sat/" -->
    <p>Not modified on a weekday; modified on Saturday 
<!--#elif expr="${LAST_MODIFIED} = /Sun/" --> 
    <p>Not modified on a weekday; modified on Sunday 
<!--#else --> 
    <p>Modified on a weekday 
<!--#endif -->

Modified on a weekday

Change LAST_MODIFIED to a different day

<!--#if expr="${LAST_MODIFIED} = /Sat/" -->
    <!--#set var="LAST_MODIFIED" value="Monday" -->
<!--#elif expr="${LAST_MODIFIED} = /Sun/" -->
    <!--#set var="LAST_MODIFIED" value="Monday" -->
<!--#else -->
    <!--#set var="LAST_MODIFIED" value="Sunday" -->
<!--#endif -->

Test if it was modified on a weekday again

<!--#if expr="${LAST_MODIFIED} = /Sat/" -->
    <p>Not modified on a weekday; modified on Saturday 
<!--#elif expr="${LAST_MODIFIED} = /Sun/" --> 
    <p>Not modified on a weekday; modified on Sunday
<!--#else --> 
    <p>Modified on a weekday 
<!--#endif -->

Not modified on a weekday; modified on Sunday

Displaying all of the environment variables

UNIQUE_ID=aBEUkWJ2dLqG1FOzmGg8bAAAAQo
HTTP_ACCEPT=*/*
HTTP_USER_AGENT=Mozilla/5.0 AppleWebKit/537.36 (KHTML, like Gecko; compatible; ClaudeBot/1.0; +claudebot@anthropic.com)
HTTP_ACCEPT_ENCODING=gzip, br, zstd, deflate
HTTP_HOST=users.cis.fiu.edu
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin
SERVER_SIGNATURE=
SERVER_SOFTWARE=Apache
SERVER_NAME=users.cis.fiu.edu
SERVER_ADDR=131.94.130.45
SERVER_PORT=80
REMOTE_ADDR=18.191.144.80
DOCUMENT_ROOT=/var/www/html
REQUEST_SCHEME=http
CONTEXT_PREFIX=/~downeyt
CONTEXT_DOCUMENT_ROOT=/home/bear-d/users/downeyt/public_html
SERVER_ADMIN=root@localhost
SCRIPT_FILENAME=/home/bear-d/users/downeyt/public_html/webdev/ssi.shtml
REMOTE_PORT=22727
GATEWAY_INTERFACE=CGI/1.1
SERVER_PROTOCOL=HTTP/1.1
REQUEST_METHOD=GET
QUERY_STRING=
REQUEST_URI=/~downeyt/webdev/ssi.shtml
SCRIPT_NAME=/~downeyt/webdev/ssi.shtml
DATE_LOCAL=Tuesday 04/29/25 (day 119) at 02:04:01 PM
DATE_GMT=Tuesday 04/29/25 (day 119) at 06:04:01 PM
LAST_MODIFIED=Sunday
DOCUMENT_URI=/~downeyt/webdev/ssi.shtml
DOCUMENT_ARGS=
USER_NAME=downeyt
DOCUMENT_NAME=ssi.shtml
fiu=www.fiu.edu

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