Server Side Includes (SSI) is a simple interpreted

server-side scripting Server-side scripting is a technique used in web development which involves employing scripts on a web server which produces a response customized for each user's (client's) request to the website. The alternative is for the web server itself ...

language used almost exclusively for the

World Wide Web The World Wide Web (WWW), commonly known as the Web, is an information system enabling documents and other web resources to be accessed over the Internet. Documents and downloadable media are made available to the network through web ...

. It is most useful for including the contents of one or more files into a web page on a web server (see below), using its #include directive. This could commonly be a common piece of code throughout a site, such as a page header, a page footer and a navigation menu. SSI also contains control directives for conditional features and directives for calling external programs. It is supported by Apache, LiteSpeed,

nginx Nginx (pronounced "engine x" ) is a web server that can also be used as a reverse proxy, load balancer, mail proxy and HTTP cache. The software was created by Igor Sysoev and publicly released in 2004. Nginx is free and open-source software ...

, IIS as well as

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's Jigsaw. It has its roots in

NCSA HTTPd NCSA HTTPd is an early, now discontinued, web server originally developed at the NCSA at the University of Illinois at Urbana–Champaign by Robert McCool and others. First released in 1993, it was among the earliest web servers developed, follo ...

. In order for a web server to recognize an SSI-enabled

HTML The HyperText Markup Language or HTML is the standard markup language for documents designed to be displayed in a web browser. It can be assisted by technologies such as Cascading Style Sheets (CSS) and scripting languages such as JavaSc ...

file and therefore carry out these instructions, either the filename should end with a special extension, by default .shtml, .stm, .shtm, or, if the server is configured to allow this, set the execution bit of the file.

Design

As a simple programming language, SSI supports only one type: text. Its

control flow In computer science, control flow (or flow of control) is the order in which individual statements, instructions or function calls of an imperative program are executed or evaluated. The emphasis on explicit control flow distinguishes an ''im ...

is rather simple, choice is supported, but loops are not natively supported and can only be done by recursion using include or using

HTTP redirect URL redirection, also called URL forwarding, is a World Wide Web technique for making a web page available under more than one URL address. When a web browser attempts to open a URL that has been redirected, a page with a different URL is opened ...

. The simple design of the language makes it easier to learn and use than most server-side scripting languages, while complicated server-side processing is often done with one of the more feature-rich programming languages. SSI is

Turing complete Alan Mathison Turing (; 23 June 1912 – 7 June 1954) was an English mathematician, computer scientist, logician, cryptanalyst, philosopher, and theoretical biologist. Turing was highly influential in the development of theoretical co ...

. SSI has a simple syntax: . Directives are placed in HTML comments so that if SSI is not enabled, users will not see the SSI directives on the page, unless they look at its source. Note that the syntax does not allow spaces between the leading "<" and the directive. Apache tutorial on SSI stipulates the format requires a space character before the "-->" that closes the element.

Examples

A web page containing a daily quotation could include the quotation by placing the following code into the file of the web page: With one change of the quote.txt file, all pages that include the file will display the latest daily quotation. The inclusion is not limited to files, and may also be the text output from a program, or the value of a system variable such as the current time.

Directives

Common

The following are SSI directives from the times of

(the 1990s). Some implementations do not support all of them.

Control directives

Control directives are later added to SSI. They include the ubiquitous if-elif-else-endif flow control and variable writing as well as more exotic features like loops only found in some implementations.

Notes

References

External links

* Language reference from implementations: ** Apache
Apache mod_include Reference
Calls directives "elements". ** Nginx

Calls directives "commands". **

Original NCSA HTTPd SSI Reference
Calls directives "commands". ** W3C Jigsaw

Calls directives "elements". Highly expanded with

servlet A Jakarta Servlet (formerly Java Servlet) is a Java software component that extends the capabilities of a server. Although servlets can respond to many types of requests, they most commonly implement web containers for hosting web application ...

JDBC Java Database Connectivity (JDBC) is an application programming interface (API) for the programming language Java, which defines how a client may access a database. It is a Java-based data access technology used for Java database connectivity. I ...

, HTTP cookie, and loops. * Tutorials:
Apache SSI Tutorial
*

*
SSI-Developer, Apache Server Side Includes
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