Editing Server Side Includes (section)

=== 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.
{| class="wikitable"
|-
! Directive
! Parameters
! Description
! Example
! Found in
|- 
| {{plainlist|
* if
* elif
* else
* endif
}}
| expr
| The [[if statement]]. Used for condition tests that may determine and generate multiple logical pages from one single physical page. <code>elif</code> is a shorthand for nested else-if. <code>else</code> and <code>endif</code> do not accept parameters.

Expression syntax vary among implementations. Variable existence and equality/regex checks are commonly supported. Jigsaw uses expressions split over multiple attributes instead.<ref name=jig/>
| <pre style="white-space:pre"><nowiki>
<!--#if expr="${Sec_Nav}" -->
<!--#include virtual="secondary_nav.txt" -->
<!--#elif expr="${Pri_Nav}" -->
<!--#include virtual="primary_nav.txt" -->
<!--#else -->
<!--#include virtual="article.txt" -->
<!--#endif -->
</nowiki></pre>
| Ubiquitous.
|- 
| set
| var, value
| Sets the value of a SSI variable. Apache provides additional parameters for [[encoding]]s.<ref name=apache-inc/> 
| <pre style="white-space:pre"><nowiki><!--#set var="foo" value="bar" --></nowiki></pre>
| Apache,<ref name=apache-inc>{{cite web |title=mod_include |url=https://httpd.apache.org/docs/current/mod/mod_include.html |website=Apache HTTP Server |access-date=25 March 2019}}</ref> Nginx<ref name="nginx">{{cite web |title=ngx_http_ssi_module |url=https://nginx.org/en/docs/http/ngx_http_ssi_module.html |website=nginx.org |access-date=25 March 2019}}</ref>
|-
| <code>printenv</code>
| &nbsp;
| This directive outputs a list of all SSI variables and their values, including environmental and user-defined variables. It has no attributes.
| <pre style="white-space:pre"><nowiki><!--#printenv --></nowiki></pre>
| Apache<ref name=apache-inc/>
|}