Explain the difference between the Apache environment and

<!--#include virtual="header.html" -->

<h1 align="center">Environment Variables in Apache</h1>

<p>Many operating systems provide a facility for storage and

transmission of information called environment variables.  Apache uses

environment variables in many ways to control operations and to

communicate with other programs like CGI scripts.  This document

explains some of the ways to use environment variables in Apache.</p>

<p>The Apache HTTP Server provides a mechanism for storing information

in named variables that are called <em>environment variables</em>.

This information can be used to control various operations such as

logging or access control.  The variables are also used as a mechanism

to communicate with external programs such as CGI scripts.  This

document discusses different ways to manipulate and use these

variables.</p>

<p>Although these variables are referred to as <em>environment

variables</em>, they are not the same as the environment variables

controlled by the underlying operating system.  Instead, these

variables are stored and manipulated in an internal Apache structure.

They only become actual operating system environment variables when

they are provided to CGI scripts and Server Side Include scripts.  If

you wish to manipulate the operating system environment under which

the server itself runs, you must use the standard environment

manipulation mechanisms provided by your operating system shell.</p>

<ul>

<li><a href="#setting">Setting Environment Variables</a></li>

<h3>SSI Pages</h3>

<p>Server-parsed (SSI) documents processed by mod_include's

<code>server-parsed</code> handler can print environment variables

<code>INCLUDES</code> filter can print environment variables

using the <code>echo</code> element, and can use environment variables

in flow control elements to makes parts of a page conditional on

characteristics of a request.  Apache also provides SSI pages with the

<!--#include virtual="header.html" -->

<h1 align="center">Environment Variables in Apache</h1>

<p>Many operating systems provide a facility for storage and

transmission of information called environment variables.  Apache uses

environment variables in many ways to control operations and to

communicate with other programs like CGI scripts.  This document

explains some of the ways to use environment variables in Apache.</p>

<p>The Apache HTTP Server provides a mechanism for storing information

in named variables that are called <em>environment variables</em>.

This information can be used to control various operations such as

logging or access control.  The variables are also used as a mechanism

to communicate with external programs such as CGI scripts.  This

document discusses different ways to manipulate and use these

variables.</p>

<p>Although these variables are referred to as <em>environment

variables</em>, they are not the same as the environment variables

controlled by the underlying operating system.  Instead, these

variables are stored and manipulated in an internal Apache structure.

They only become actual operating system environment variables when

they are provided to CGI scripts and Server Side Include scripts.  If

you wish to manipulate the operating system environment under which

the server itself runs, you must use the standard environment

manipulation mechanisms provided by your operating system shell.</p>

<ul>

<li><a href="#setting">Setting Environment Variables</a></li>

<h3>SSI Pages</h3>

<p>Server-parsed (SSI) documents processed by mod_include's

<code>server-parsed</code> handler can print environment variables

<code>INCLUDES</code> filter can print environment variables

using the <code>echo</code> element, and can use environment variables

in flow control elements to makes parts of a page conditional on

characteristics of a request.  Apache also provides SSI pages with the