There are 3 ways to use CGI.

• First Way
  When we install Apache server, then /usr/lib/cgi-bin folder is automatically created. You can place c++ files in that folder and execute them on browser(localhost/cgi-bin/example).
• Second Way
  You can also configure /var/www/cgi-bin for CGI programming.
• Third Way
  You can also configure cgi-bin in home directory as /public_html/cgi-bin.

According to me 3rd way is best as its in home directory and we don’t have to use sudo while compiling or creating any file.

Steps to configure cgi-bin in public_html and public_html. Run following commands in terminal

1. $ sudo a2enmod cgi
2. $ sudo a2enmod cgid
3. $ sudo a2enmod userdir
4. $ sudo service apache2 restart
5. $ mkdir ~/public_html
6. $ cd ~/public_html
7. $ mkdir cgi-bin
8. $ cd /etc/apache2
9. $ sudo vim sites-available/default
10. Add following text in file:

     ScriptAlias /cgi-bin/ /home/*/public_html/cgi-bin/
     <Directory "/home/*/public_html/cgi-bin">
             AllowOverride None
             Options +ExecCGI -MultiViews +SymLinksIfOwnerMatch
             SetHandler cgi-script
             Order allow,deny
             Allow from all
     </Directory>
    

11. $ sudo service apache2 restart