HoTMetaL PRO 4.0: CGI Scripts: CGI Basics

OVERVIEW

CGI (Common Gateway Interface) scripts are used on Web pages for a variety of applications. A simple CGI script could allow you to have a response form, a guestbook, or an access counter for your Web page. More complicated uses of CGI include querying and updating a database of customer information and then tailoring the information presented on your web site to each customer's known preferences. Several sample CGI scripts have been included with HoTMetaL PRO. They can be found in the CGI directory off of the installation directory.

CGI scripts allow users to interact with other software and databases that may be on a World Wide Web server. A CGI script can be called implicitly from an HTML page, or it can be invoked explicitly through a fill-in form in which the user provides information and then submits it to the Web server. Originally, CGI scripts were designed to interact with the CERN and NCSA Web servers; consequently, there is a strong UNIX influence in CGI scripts. UNIX scripts can be written in a number of languages, but the most popular by far is PERL (see references below). CGI scripts can also be implemented on other platforms, though the resources available for them are not as plentiful. Scripts to work with the MacHTTP (the hypertext transfer protocol which runs on the Macintosh) can be written in AppleBasic, Frontier and MacPerl. DOS and Windows users will be familiar with .BAT files, which can run as CGI scripts.

Writing and implementing CGI scripts is not a trivial exercise. Because a script can receive input from a user and then process that input, there are security risks for the host system. Usually, the installation of a CGI script requires the permission of the 'webmaster', the person who maintains the Web server on your system. You should consult your webmaster before using any CGI scripts. You should also be wary of downloading and using scripts from the Internet unless the resource is well-known and respected (such as the NCSA), particularly if you do not understand exactly what the script was written to do. Most CGI scripts are well-intentioned helper-applications, but there are some which mimic the destructive effects of computer viruses and could damage the data on your system.

IMPLEMENTATION

Each CGI script is located in a separate directory below this one with its supporting documentation and files (if any). All of the CGI scripts included with HoTMetaL are written in PERL. Before installing one of the cgi scripts included with HoTMetaL PRO, you should do the following:

• Check with your webmaster to make sure he/she wants you to install the scripts. If he/she confirms that you can install the script, check where you should place it. It is generally in the cgi-bin directory of the server software.
• Edit the first line of each .pl script. This line tells the script where PERL is located on your system (you must be running perl for these scripts to work). If you type 'which perl' at your system prompt, you will get the full system path.
• Follow the instructions in the readme.txt files for configuring the script for your server. Some scripts only have one variable you need to change, others have several. You should make these changes with a text editor and not a word processing program.
• After all the changes have been made to the script, copy it to the location your webmaster specified (if the write permissions are restricted on this directory, your webmaster may have to do this for you.)
• Make sure that the HTML files which call these scripts have been edited as well and that they are pointing to the correct script (your webmaster can help you with this).

You will probably have to do some tweaking on these files once they have been installed; CGI scripts never work the first time :-).

DISCLAIMER

SoftQuad provides these scripts as is and makes no guarantees to their accuracy. SoftQuad will also not provide support for these scripts. Check with your local systems personnel; they will be the best qualified to help you with any CGI problems that might occur.

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