Introduction to Server Side Includes Fort Collins, CO Copyright © XTR Systems, LLC Introduction to Server Side Includes (SSI) Instructor: Joseph DiVerdi, Ph.D., MBA

Introduction to Server Side Includes Fort Collins, CO Copyright © XTR Systems, LLC Server Side Includes Server-Side, HTML-Embedded Language –Directives Included in HTML Document Also Known As Commands or Placeholders –Replaced By The Server With HTML Content Never Seen By the Browser Looks Just Like Regular-old HTML Not So Powerful As CGI Saves You the Trouble of Writing Complete CGI Programs

Introduction to Server Side Includes Fort Collins, CO Copyright © XTR Systems, LLC Server Side Includes Server Receives Request for Document Server Examines Document Content –Looking for SSI Directives Process Known As "Parsing the File" Server Replaces Directives With HTML Data –Current Time & Date –Contents of Another File –Last Modified Time & Date Transmits Document to Client

Introduction to Server Side Includes Fort Collins, CO Copyright © XTR Systems, LLC SSI Interaction

Introduction to Server Side Includes Fort Collins, CO Copyright © XTR Systems, LLC SSI Usage Create Framework for Pages Which Are Dynamically Generated –Elements Which Are Repeatedly Used Navigation Bar or Header –Elements Which Are Changing Message of the Day Last Modified Date Current Time & Date –Elements Dependent on Environment Variables Content Varied by Browser Type

Introduction to Server Side Includes Fort Collins, CO Copyright © XTR Systems, LLC SSI Advantages There Are Many Advantages To Using SSI: –Shallow Learning Curve Fairly Easy To Learn –Broad Support of SSI by Several Different Servers –Up-To-The-Minute Information to Viewers –No Browser Dependence Like JavaScript Dependent Upon Server –SSI Cannot Be Seen by Viewers Unlike JavaScript –Easier to Implement Than Full-up CGI Programs

Introduction to Server Side Includes Fort Collins, CO Copyright © XTR Systems, LLC SSI Disadvantages Yes, There Are Some Disadvantages: –It Takes More Work for Server to Parse & Deliver Documents Than to Deliver Documents Slower Response Per Document and/or Limited Ability to Handle High Request Rate –Greater Security Risk Principally If Command Execution is Enabled –SSI Directives Are Limited In Power Need More? Use PHP and/or CGI

Introduction to Server Side Includes Fort Collins, CO Copyright © XTR Systems, LLC To Use Or Not To Use A Matter of How Much of the Page Is Static –How Much Needs to Be Recalculated Every Time the Page Is Served SSI Is a Great Way to Add Small Pieces of Information If a Majority of Your Page Is Being Generated at the Time That It Is Served, You Need Another Solution

Introduction to Server Side Includes Fort Collins, CO Copyright © XTR Systems, LLC SSI Syntax All SSI Directives Use the Format: Where: –Directive Is Contained in an HTML Comment –Command Begins With a Sharp - "#" –There Is No Space Between Comment Start & Sharp –Command Is an SSI Keyword –arg1, arg2,... Are the Names of the Arguments –value1, value2,... Are the Values of The Arguments –Quotes Are Not Always Required Around Values But a Very Good Idea

Introduction to Server Side Includes Fort Collins, CO Copyright © XTR Systems, LLC SSI Syntax Allowed Commands: –echo –include –fsize –flastmod –exec –printenv –set –is, elif, else, endif –config

Introduction to Server Side Includes Fort Collins, CO Copyright © XTR Systems, LLC HTML-Embedded Language Before Transmitting Document to Client Server Examines Document Looking for SSI Directives –Also Known As "Parsing the File" Server Then Inserts Requested Data

Introduction to Server Side Includes Fort Collins, CO Copyright © XTR Systems, LLC SSI Document on Server Current Time It is now:

Introduction to Server Side Includes Fort Collins, CO Copyright © XTR Systems, LLC HTML received by Client Current Time It is now: 6:10 PM (MT) on May 15, 1865

Introduction to Server Side Includes Fort Collins, CO Copyright © XTR Systems, LLC Dynamic Content Using SSI Current Time It is now: Create a File Named ssi_test.shtml File Must Have a ".shtml" Suffix to Work

Introduction to Server Side Includes Fort Collins, CO Copyright © XTR Systems, LLC Dynamic Content Using SSI Current Time It is now: Last modified:

Introduction to Server Side Includes Fort Collins, CO Copyright © XTR Systems, LLC Dynamic Content Using SSI Current Time It is now: Last modified: Welcome to my server at:

Introduction to Server Side Includes Fort Collins, CO Copyright © XTR Systems, LLC Dynamic Content Using SSI Current Time It is now: Last modified: Welcome to my server at: Your host's IP address is: Your host's name is:

Introduction to Server Side Includes Fort Collins, CO Copyright © XTR Systems, LLC Dynamic Content Using SSI Current Time It is now: Last modified: Welcome to my server at: Your host's IP address is: Your host's name is: Your user agent is:

Introduction to Server Side Includes Fort Collins, CO Copyright © XTR Systems, LLC Environment Variables Create a File Named env.shtml

Introduction to Server Side Includes Fort Collins, CO Copyright © XTR Systems, LLC Server Configuration Server Must Know Which Documents to Parse for SSI Directives –Too Much Server Load to Parse Every Document Several Server Options –Parse Certain Directory or Directories –Parse Documents With Certain Extensions Usually ".shtml" Security-Minded Server Option –Enable External Program Execution

Introduction to Server Side Includes Fort Collins, CO Copyright © XTR Systems, LLC Server Configuration Site Administrator Enables SSI –On a Directory-By-Directory Basis –Performed Using Server Configuration File –Server Must be Restarted For Changes To Take Effect

Introduction to Server Side Includes Fort Collins, CO Copyright © XTR Systems, LLC Sample Server Configuration Options MultiViews IncludesNoExec AllowOverride FileInfo AuthConfig Limit "Options Includes" –Server-Side Includes Are Permitted "Options IncludesNoExec" –Server-Side Includes Are Permitted –The #exec Command Is Disabled linus Is Configured With IncludesNoExec

Introduction to Server Side Includes Fort Collins, CO Copyright © XTR Systems, LLC Server Configuration Site Administrator May Set Server Configuration To Permit You To Enable SSI Yourself –Using Directory-Specific htaccess Files Directives Are Not Just For Authentication They Are General Purpose Tools

Introduction to Server Side Includes Fort Collins, CO Copyright © XTR Systems, LLC Server Configuration Options MultiViews AllowOverride FileInfo AuthConfig Limit Options "AllowOverride Options" –Permits the Web Developer to Enable Certain Features & Functions –On a Directory-by-directory Basis –Using htaccess Files

Introduction to Server Side Includes Fort Collins, CO Copyright © XTR Systems, LLC Sample htaccess File Options +IncludesNoExec –Server-Side Includes Are Permitted –The #exec Command Is Disabled –Plus Indicates That This Directive Merges Options Directives With Those Already In Effect Rather Than Superceding Them The Use of This Directive Is Not Necessary On linus Because SSI Is Already Enabled

Introduction to Server Side Includes Fort Collins, CO Copyright © XTR Systems, LLC SSI Without Extensions Server Efficiency Requires Selective Use of SSI –Because of Additional Server Load Caused by Document Parsing Using a Special Extension Is One Way to Do It –Obvious to Knowledgeable Viewer –Inclusion or Exclusion Requires Links Update It Is Possible to Identify SSI Documents –Behind the Scenes –Without the Use of a Special Extension –Without Letting the Viewer Know About It

Introduction to Server Side Includes Fort Collins, CO Copyright © XTR Systems, LLC SSI Without Extensions Use a Directive Known As XbitHack –Enable SSI in a Particular Directory or Entire Server Same Location Rules As Options & AllowOverride Directives Used in Server Configuration File or htaccess Files Use File Permissions –Enable SSI on a Particular File

Introduction to Server Side Includes Fort Collins, CO Copyright © XTR Systems, LLC SSI Without Extensions Use a Directive Known As XBitHack –Enable SSI in a Particular Directory or Entire Server Same Location Rules As Options & AllowOverride Directives Used in Server Configuration File or htaccess Files Use File Permissions –Enable SSI on a Particular File This is Only Available on UNIX Servers –Because Only UNIX Offers Suitable File Permissions

Introduction to Server Side Includes Fort Collins, CO Copyright © XTR Systems, LLC XBitHack Directive Syntax: XBitHack on | off | full –Default is off –off - No special treatment of executable files –on - Any File That With User-Execute Bit Set Will Be Treated As an SSI HTML Document User-Execute Bit Is Also Known As Owner-Execute Bit –full - For More Information See:

Introduction to Server Side Includes Fort Collins, CO Copyright © XTR Systems, LLC Adding a htaccess File Create htaccess File in Your HTML Directory Edit It to Include the Following: XBitHack on That's It

Introduction to Server Side Includes Fort Collins, CO Copyright © XTR Systems, LLC Setting the User-Execute Bit Standard Procedure –Provide the Minimum Amount of Permission to Each File to Accomplish Goal For HTML Files This Means 644 in Octal Format rw-r--r-- in Bit Format –User: Read, Write –Group: Read –Other: Read

Introduction to Server Side Includes Fort Collins, CO Copyright © XTR Systems, LLC Setting the User-Execute Bit To Signal That a Particular HTML File Contains SSI Turn on the User Execute Bit For HTML Files This Means 744 in Octal Format rwxr--r-- in Bit Format –User: Read, Write, Execute –Group: Read –Other: Read

Introduction to Server Side Includes Fort Collins, CO Copyright © XTR Systems, LLC SSI Without Extensions Modify ssi_test.shtml File –Change Extension to ".html" Use Html-Kit to Accomplish This Task –Change Permission From 644 to 744 Use Tera Term Pro to Accomplish This Task –Log In to Your Account –Navigate to Appropriate Directory Using cd Command cd html –Use Change Mode Command: chmod 744 ssi_test.html Test ssi_test.html Using Your Browser

Introduction to Server Side Includes Fort Collins, CO Copyright © XTR Systems, LLC The #exec Command

Introduction to Server Side Includes Fort Collins, CO Copyright © XTR Systems, LLC Including Files

Introduction to Server Side Includes Fort Collins, CO Copyright © XTR Systems, LLC Included Files & LAST_MODIFIED

Introduction to Server Side Includes Fort Collins, CO Copyright © XTR Systems, LLC Conditional Execution

Introduction to Server Side Includes Fort Collins, CO Copyright © XTR Systems, LLC Modifying Timestamp Format

Introduction to Server Side Includes Fort Collins, CO Copyright © XTR Systems, LLC Accessing the Query String

Introduction to Server Side Includes Fort Collins, CO Copyright © XTR Systems, LLC Apache SSI Documentation Apache Organization "How-To" Apache Week Short Tutorial