Apache Variables

Apache Variables are not supported by defaultby apache but you can do two things to achieve this functionality::

Option 1 – Use system variables
Option 2 – Use mod_macro

Applicable to

Centos 6.x

This article was written with instructions for Centos 6.x, but the concept applies any distibution.

Option 1 – System Variables

Add variables in init script

To set environment variables in your Apache init script (/etc/init.d/httpd) before the line that calls httpd. For example, add:

MYVAR=value

Better would be to store all the variables in an external file, for example you can call it: /etc/httpd/conf/vars.txt and add to it all your variables:

MYAPP=/path/to/dir
BAR=/path/to/dir

and then include these into your Apache init.d script with:

. /etc/httpd/conf/vars.txt

you can also reload the file into memory by using the last command on shell.

to check that the variables added to your system variables use the set command:

set

Using inside configuration

Variables can be used in the configuration like so:

${MYVAR}

The variables can be used anywhere.

You can pass the variable into your CGI scripts and SSI pages using mod_env by adding to your confs:

PassEnv LD_LIBRARY_PATH

Option 2 – mod_macro

You can use apache Variables as functions using mod_macro extension,

mod_macro enables you to create macro functions with variables like:

<Macro VHost $host $port $dir>
  Listen $port
  <VirtualHost *:$port>

    ServerName $host
    DocumentRoot $dir

    <Directory $dir>
      # do something here...
    </Directory>

    # limit access to intranet subdir.
    <Directory $dir/intranet>
      order deny,allow
      deny from all
      allow from 10.0.0.0/8
    </Directory>
  </VirtualHost>
</Macro>

## Use of VHost with different arguments.

Use VHost www.apache.org 80 /projects/apache/web
Use VHost www.perl.com 8080 /projects/perl/web
Use VHost www.ensmp.fr 1234 /projects/mines/web

* example taken from here.

Prerequisites for mod_macro

The scripts in the article uses wget: yum install wget
apxs: yum install httpd-devel.i386
apache version 2.3

check your apache version using:
httpd -v

centos repository have apache 2.2.15, so you’ll need to compile newer version from source which is out of the bounds of this article. if you have later version of apache you can still use mod_macro which is better solution (for me) over system variables