Running CGI Scripts on Apache2

30 Sep 2015 #apache #ubuntu #cgi #python

Intro

Have you ever wanted to create a webpage or process user input from a web-based form using Python? These tasks can be accomplished through the use of Python CGI (Common Gateway Interface) scripts with an Apache web server. CGI scripts are called by a web server when a user requests a particular URL or interacts with the webpage (such as clicking a “Submit” button). After the CGI script is called and finishes executing, the output is used by the web server to create a webpage displayed to the user.

If you just want to test the waters in the CGI world, you might wanna test your scripts in a simple server like the one shipped with python default.

I have written an article on that. Here’s the link.

Running-CGI-Sripts-with-CGIHTTPServer

Configuring the Apache2 Web server to run CGI scripts

I am assuming that you are using apache2 version 2.4.*, as in Apache2.4, the configuration was cleaned up considerably, and things in the default site definition have been moved to configuration files in conf-available. Among other things, this also includes the CGI-related configuration lines seen in the default site of older versions. These have been moved to /etc/apache2/conf-available/serve-cgi-bin.conf, which contains:

ScriptAlias /cgi-bin/ /usr/lib/cgi-bin/

Just to check whether you have apache2 installed on your system and its up and running do a

tasdik@Acer:~$ apache2 -v
Server version: Apache/2.4.10 (Ubuntu)
Server built:   Mar  5 2015 18:13:03
tasdik@Acer:~$

I am currently on version 2.4. If you don’t get any output from the prompt its likely that you don’t have it installed on your system. Just do a

tasdik@Acer:~$ sudo apt-get install apache2

Anyways, You just need to make changes on two configuration files, them being

/etc/apache2/apache2.conf
/etc/apache2/conf-available/serve-cgi-bin.conf

On the terminal

tasdik@Acer:~$ mkdir /var/www/cgi-bin
tasdik@Acer:~$ cd /var/www/cgi-bin/
tasdik@Acer:/var/www/cgi-bin$ sudo nano /etc/apache2/apache2.conf

And add the following at the end

###################################################################
#########     Adding capaility to run CGI-scripts #################
ServerName localhost
ScriptAlias /cgi-bin/ /var/www/cgi-bin/
Options +ExecCGI
AddHandler cgi-script .cgi .pl .py

This converts the cgi-bin address to the specified address and the AddHandler tells the server to treat all files with .cgi,.pl and .py extensions as cgi scripts.

Now for the second conf file

tasdik@Acer:~$ sudo nano /etc/apache2/conf-available/serve-cgi-bin.conf

The final file should look something like this

<IfModule mod_alias.c>
	<IfModule mod_cgi.c>
		Define ENABLE_USR_LIB_CGI_BIN
	</IfModule>

	<IfModule mod_cgid.c>
		Define ENABLE_USR_LIB_CGI_BIN
	</IfModule>

	<IfDefine ENABLE_USR_LIB_CGI_BIN>
		#ScriptAlias /cgi-bin/ /usr/lib/cgi-bin/
		#<Directory "/usr/lib/cgi-bin">
		#	AllowOverride None
		#	Options +ExecCGI -MultiViews +SymLinksIfOwnerMatch
		#	Require all granted
		#</Directory>

		## cgi-bin config
		ScriptAlias /cgi-bin/ /var/www/cgi-bin/
	    <Directory "/var/www/cgi-bin/">
	        AllowOverride None
	        Options +ExecCGI
	    </Directory>

	</IfDefine>
</IfModule>

# vim: syntax=apache ts=4 sw=4 sts=4 sr noet

Now restart the apache2

tasdik@Acer:~$ sudo service apache2 restart

Creating a simple CGI script

We have to first create the folder that will hold the cgi-scripts, so lets do that.

tasdik@Acer:~$ cd /var/www/cgi-bin
tasdik@Acer:/var/www/cgi-bin$ touch hello.py
##  make it executable for you and others

tasdik@Acer:/var/www/cgi-bin$ chmod o+x hello.py

##  Put the following content just for testing inside `hello.py`
tasdik@Acer:/var/www/cgi-bin$ sudo nano hello.py

Add the following to hello.py

#!/usr/bin/env python

import cgitb
cgitb.enable()
print("Content-Type: text/html;charset=utf-8")

print "Content-type:text/html\r\n\r\n"
print '<html>'
print '<head>'
print '<title>Hello Word - First CGI Program</title>'
print '</head>'
print '<body>'
print '<h2>Hello Word! This is my first CGI program</h2>'
print '</body>'
print '</html>'

Run the Script:

Open your browser and enter the following link

http://localhost/cgi-bin/hello.py

And the script should run just fine.

Debugging :

If the script is not running, you can check the logs stored in

/var/log/apache2/error.log

You can also refer the official reference here : http://httpd.apache.org/docs/2.0/howto/cgi.html

Hope it helped!

Tasdik Rahman