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Common Gateway Interface (CGI) definition

Common Gateway Interface (© Vege /

Common Gateway Interface (© Vege /

Common gateway interface (CGI) is the standard for interfacing external programs with information servers on the World Wide Web. Essentially, it provides a standard protocol that is used by web servers to execute programs that run on a server and generate web pages. These programs are known as CGI scripts, and the details of how a script is executed by a server are determined by the server itself.


Example of Common Gateway Interface

Common gateway interface refers to a set of rules that apply to running scripts and programs across a server on the Internet. It specifies what type of information is communicated between a web server and web browsers, and how that information is transmitted. It is the standard for interfacing eternal programs with information servers on the web.

Common gateway interface is differentiated from a plain HTML document because a plain HTML document is static, whereas a common gateway interface is executed in real-time in order to output a tremendous amount of information. In other words, a program that utilizes common gateway interface is executable, while the plain HTML document remains a constant text file that cannot be changed. Common gateway interface gathers information from users across the web and customizes pages to their specific needs. Though there are more advanced ways to execute the same type of actions, common gateway interface is much more versatile. This is why, over time, it has become the generalized way to refer to any program that is run on a web-based server and interacts with a browser.

A good example of common gateway interface is as follows:

If you wanted to make it possible for people around the globe to query a database that you have created, you could develop an executable common gateway interface script that would be able to send information directly to the database engine, which would allow you to receive results and place them in a user’s web browser. That user would not be able to directly access the database without type of gateway providing access. The link between the database and the user is referred to as the “gateway”, which is exactly where the common gateway interface standard originated from.

Importance of Common Gateway Interface

The significance of common gateway interface is directly related to the fact that it offers flexibility and versatility which have made is the standard for running executable files from web-based servers. This makes real interactivity possible in a myriad of ways across websites.

For instance, common gateway interface scripts can employ the following types of features:

  • Advertisements
  • Access counters
  • Audio management
  • Auctions
  • Calendars
  • Bulletin board systems
  • Chats
  • Classified ads
  • Retrieval of content
  • Clocks
  • Finance and commerce
  • Customer support
  • File management
  • Games
  • HTML manipulation
  • Instant messaging
  • Verification of links
  • Mailing lists
  • Password protections
  • Shopping carts
  • Searches
  • Prevention of spam
  • Web-based email systems
  • Promotions of websites
openPR tip: And so much more! Common gateway interface really makes it possible to do anything on the web.

How Scripts for Common Gateway Interface Work

Though it might seem like a complex process, the manner in which a common gateway interface script works is really rather simple and straightforward. Essentially, the process involves the following:

  • A user completes a form and submits it, which sends that information to the web server.
  • The web server retrieves the information that the user entered into the form and sends it to common gateway interface software.
  • The common gateway interface software executes a validation of the information that it has received; for example, it checks the validity of an email address.
  • The software executes the prepared database statement, which is then passed onto the database driver.
  • Essentially, the database river is the middleman. It performs the action that has been requested on the database.
  • The results of the action that was performed on the database are passed to the database driver.
  • Information from the database driver is sent to the common gateway interface software.
  • The software uses the information and transforms it into the desired format.
  • Should static HTML pages need to be made, the common gateway interface will access the file system of the web server to read, write or edit files, as needed.
  • The software transmits the results that it wants to the user’s browser to see back over to the web server.
  • The server transmits the results that it received from the common gateway interface software to the user’s browser.
openPR tip: While it might be a lot to digest, the process is actually rather easy and it occurs in virtually no time. It really is quite remarkable.

The Benefits of Common Gateway Interface

Though the applications that common gateway interface can execute can be implemented in other ways, they aren’t as versatile. Common gateway interface truly is the standard, and most programmers would simply rather make improvements to their old scripts so that they can be used in new ways than start from the bare bones.

The Disadvantages of Common Gateway Interface

Despite the benefits, there are some disadvantages associated with common gateway interface. For example, a lot of the newer languages that have been developed are slow. Additionally, there are some significant security issues that have been linked to common gateway interface.