CGI Proxy - Common Gateway Interface Proxy
============================================

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        **What is CGI?**

        CGI stands for Common Gateway Interface. It is a standard protocol used by web servers to interface with executable programs (scripts or binaries) to generate dynamic content on web pages.

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        **Why is CGI useful?**

        * Enables the generation of dynamic web content.
        * Allows web servers to execute external scripts or applications (e.g., in Python, Perl, C).
        * Facilitates form handling, database interaction, and content customization.
        * Can integrate legacy applications with modern web servers.

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        **How it works?**

        * A user requests a web page that uses CGI (e.g., a `.cgi` or `.pl` script).
        * The web server receives the request and invokes the CGI program.
        * The program processes input (such as form data) and generates output, usually HTML.
        * The server sends this output back to the user's browser as the HTTP response.

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        **Where is CGI used?**

        * In early dynamic websites and legacy systems.
        * For simple form handling or server-side scripting tasks.
        * In systems where lightweight or custom server scripting is required.
        * Still used in some internal tools or embedded systems.

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        **Which OSI layer does this protocol belong to?**

        * CGI operates at the **Application Layer (Layer 7)** of the OSI model.
        * It is invoked by web servers (like Apache or Nginx) to serve HTTP requests with dynamic content.

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        **IS CGI windows specific?**

        * No, CGI is not Windows-specific.
        * It is supported on both Windows and Unix-like systems, including Linux and macOS.

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        **IS CGI Linux Specific?**

        * No, CGI is not Linux-specific.
        * Though it is commonly used in Linux web environments, it is cross-platform and works wherever a compatible web server and interpreter are available.


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        Topics in this section,

                * :ref:`Learnings in this section <CGI_step1>`

                * :ref:`Terminology <CGI_step2>`

                * :ref:`Version Info <CGI_step3>`

                * :ref:`CGI Version&IEEE Details <CGI_step5>`

                * :ref:`CGI Basic Setup on Ubuntu using IPv4 <CGI_step18>`

                * :ref:`CGI Basic Setup on Ubuntu using IPv6 <CGI_step19>`

                * :ref:`CGI Protocol Packet Details <CGI_step6>`

                * :ref:`CGI Usecases <CGI_step7>`

                * :ref:`CGI Basic Features <CGI_step8>`
                    
                * :ref:`Reference links <CGI_step17>`


.. _CGI_step1:

.. tab-set::

    .. tab-item:: Learnings in this section

        * In this section, you are going to learn

.. _CGI_step2:

.. tab-set::

    .. tab-item:: Terminology
        
       * Terminology


.. _CGI_step3:

.. tab-set::

    .. tab-item:: Version Info
    
         * Version Info

.. _CGI_step5:

.. tab-set::

    .. tab-item:: CGI Version&RFC Details

        * rfc details

.. _CGI_step18:

.. tab-set::

    .. tab-item:: CGI Basic Setup on Ubuntu using IPv4

       * setup

.. _CGI_step19:

.. tab-set::
  
   .. tab-item:: CGI Basic Setup on Ubuntu using IPv6

     * setup
       
.. _CGI_step6:

.. tab-set::

    .. tab-item:: CGI Protocol Packet Details

        * packet details
       


.. _CGI_step7:

.. tab-set::

    .. tab-item:: CGI Usecases

       * usecases
        
        

.. _CGI_step8:

.. tab-set::

    .. tab-item:: CGI Basic Features
    
        * features 



.. _CGI_step17:

.. tab-set::

    .. tab-item:: Reference links
     
       * Reference links