How to Define & Use Variables in Apache httpd.conf

Sometimes you may need to set special variables in Apacher server configuration and be able to use them later. You can easily do this using Define directive. In this article, we will look at how to define & use variables in Apache httpd.conf.

How to Define & Use Variables in Apache httpd.conf

Here are the steps to define & use variables in Apache httpd.conf using Define directive. Here is its syntax.

Define variable_name variable_value

You need to mention the variable name and its value after Define keyword.

For example, let us say you want to create a variable file_path as /home/project/files then add the following Define directive to your httpd.conf file.

Define file_path /home/project/files

Open Apache configuration file using a text editor.

$ sudo vi /etc/apache2/httpd.conf

Add the above mentioned directive to this file.

Define file_path /home/project/files

Save and close the file. Restart Apache server to apply changes.

$ sudo service apache2 restart

You can also use the above variable in your Apache configuration file, to define other variables, or in Server tags such as Directory, VirtualHost, etc. Here are a couple of examples.

ServerRoot = ${file_path}
OR
DocumentRoot = ${file_path}
OR
<Directory ${file_path}>
...
</Directory>

If you want to access the value of your variable, you need to use the variable name inside ${…}

You can also define multiple variables and combine them as shown below. In the following example, we define file_path and root_path as two variables and concatenate their values at various places.

file_path = /docs/data
root_path = /home/user

ServerRoot = ${root_path}${file_path}
OR
DocumentRoot = ${root_path}${file_path}
OR
<Directory ${root_path}${file_path}>
...
</Directory>

As you can see it is very easy to define and use variables in Apache server.

Also read:

NGINX: Protect Static Files with Authentication
How to Setup Apache Virtual Hosts in Windows
How to Escape Percent Symbol in Apache
How to Log Post Data in NGINX
How to Read POST data in NodeJS