Frequently Asked Questions on using CGI programs in IOHK's World Wide Web Server: (Version 2)

written by Ashley Cheng, June 1997

Content:

1. What is new in this version?
2. What is covered in this FAQ?
3. What is NOT covered in this FAQ?
4. What is CGI?
5. What constitutes a CGI program?
6. Which CGI programs/scripts are available in IOHK's Web Server and how to make use of them in my home-page?
   • Access Counter
   • Imagemap
   • Feedback Form
   • Current Date and Time
   • Calendar
   • Finger Gateway
7. Can I execute a script/program placed in my own home-directory from a Web Page?
8. Then will I be able to make use of my own CGI scripts or programs in IOHK's Web Server?
9. Where can I find more information about CGI?
10. Who is Ashley Cheng??

1. What is new in this version?

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Some cool things that can be done with CGI programs include on-line database searching, feedback form, image-map, access counter and on-line ordering.

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I personally prefer PERL for several reasons: it is a scripting language which needs no compilation before it will run and is easier to debug and maintain than a compiled program; it is optimized for easy manipulation of text, files and processes; it is portable and available in most platforms.

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5. Which CGI programs/scripts are available in IOHK's Web Server and how to make use of them in my home-page?

• Access Counter

  The nph-count program helps you keep track of the number of hits to your home-page by generating on the fly an odometer like counter image and displaying it in the calling home-page.

  To activate a counter in a certain HTML-page add something like:

  < IMG SRC="http://www.iohk.com/cgi-bin/nph-count?arg1=value1&arg2=value2&arg3=value3">

  where arg1,2,3 are any of the supported arguments.

  Recognised arguments include:

  • width=number
    Specifies the number of digits in the resulting image.
  • link=string
    A string unique to your counter. URL of the page on which the counter is located. A good choice is the URL of the page on which the counter image is located.
  • increase=number; default 1
    Specifies the number by which the counter should be increased.
  • show=NO
    Specify this argument if you just want to keep track of the number of accesses to a certain page without showing the counter image

  Example: <IMG SRC="http://www.iohk.com/cgi-bin/nph-count?link=cgifaq&width=5>, and the resulting image will resemble the image below:

  

  For a real-life example please see http://www.iohk.com/UserPages/acheng. For more information on the nph-count program, please refer to Frequently Asked Questions (FAQ) about WWW-page Access counter. To learn more about Access counter in general, take a look at Yahoo's Access Count Resource Page

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• ImageMap

  An imagemap is a graphical overview of any set of information resources. By clicking on different parts of the overview image, users can transparently access any of the information resources. For real-life examples, take a look at http://www.wahyan.edu.hk and www.ha.org.hk/qmh.

  First step: create an image to serve as the map.

  The image could either be in GIF or JPG format. You could use any graphic programs which produce files in GIF or JPG format (e.g. Adobe Photoshop, CorelPhotoPaing etc) that you are familiar with. I personally use Adobe Photoshop 3.05. The image should then be placed somewhere in your home-directory on www.iohk.com.

  Second step: prepare the map information file.

  This file maps regions to URLs for the given image. IOHK's server uses the NCSA Map file format. Lines beginning with # are comments. Every other non-blank line consists of the following:

  method URL coord1 coord2 ... coordn

  method is one of the following:

  • default - For the default URL; Coordinates: none
  • circle - For a circle; Coordinates: center edgepoint
  • poly - For a polygon of at most 100 vertices; Coordinates: Each coordinate is a vertex.
  • rect - For a rectangle; Coordinates: upper-left lower-right
  • point - For closest to a point; Coordinate: thePoint

  URL is one of the following:

  • A Local URL - eg. /mydir/myhtml.html
  • A Full URL - eg. http://www.iohk.com/

  coord#: Each coord entry is a coordinate, format x,y. The number depends on the method.

  The map file that the home-page of Wah Yan College used is shown below:

  default http://www.wahyan.edu.hk/Welcome.html
  rect    http://www.wahyan.edu.hk/alma/Welcome.html         15,11    229,160
  rect    http://www.wahyan.edu.hk/oldboys/Welcome.html      256,10   474,158  
  rect    http://www.wahyan.edu.hk/interest/Welcome.html     14,181   229,328  
  rect    http://www.wahyan.edu.hk/news/Welcome.html         257,180  473,329 
  

  For a list of tools that may help you create a map file, see Yahoo's Imagemap Directory. For example, MapTHIS! is a good freeware WYSIWYG image map editor/creator for those who work under Windows platform.

  It doesn't matter what you name your map file but it is customary to give it a *.map extension. After creating the map file place it somewhere inside your home-directory on www.iohk.com. For example, the map file of Wah Yan College (wahyan.map) resides in http://www.iohk.com/UserPages/acheng.

  Third step: referencing the map information file from your map image

  • Display the image in your home-page by using the <IMG> tag and stating that it is an imagemap with the ISMAP option:
    < IMG SRC="http://www.iohk.com/UserPages/your_home_dir/image_filename" ISMAP>

  • Link the image to your map information file (note carefully how the map info file is referred to) :
    Say your map info file is www.iohk.hk/UserPages/your_home_dir/map_filename,
    you should refer to it as:

    <A HREF="http://www.iohk.com/UserPages/your_home_dir/map_filename">
    < IMG SRC="http://www.iohk.com/UserPages/your_home_dir/image_filename" ISMAP>
    < /A>

    Example:

    < A HREF="http://www.iohk.com/UserPages/acheng/wahyan.map">
    < IMG SRC="http://www.iohk.com/UserPages/acheng/wymap.gif" ISMAP>
    < /A>

    Note: It is no longer necessary to include the path "cgi-bin/imagemap" when you refer to the map file as described in the previous version of this FAQ.

  That's it!! Now you have an imagemap in your home-page. For more information on Imagemap, read NCSA ImageMap Tutorial.

  Note: Certain newer browsers such as Netscape navigator 2.0 and Microsoft Internet Explorer, support Client Side Imagemaps. Check out http://www.spyglass.com/techspec/img_maps.html for more information on that.

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• Feedback Form

  IOHK's server has installed a freeware CGI PERL script, FormMail.pl, by Matt Wright which allows you to create any feedback form you wish and then by imbedding certain hidden form elements the results will be mailed back to you.

  First Step:

  Create a FORM as usual. Include as many fields as you like. For more information on how to create a form, see Yahoo's Form resource Page.

  Second Step:

  Make a reference to the script from your FORM by specifying it in the ACTION option:

  < FORM METHOD="post" ACTION="http://www.iohk.com/cgi-bin/FormMail.pl">

  Third Step:

  Modify the behaviour of FormMail.pl so that it works for you by adding several HIDDEN fields in your FORM:

  • Email address of recipient. This is required. All other fields are optional.
    < INPUT TYPE="hidden" NAME="recipient" VALUE="your_email_address">

  • Subject of the return email. Optional.
    < INPUT TYPE="hidden" NAME="subject" VALUE="put_your_subject_here">

  • Fields in your form that MUST be filled in. Optional.
    < INPUT TYPE="hidden" NAME="required" VALUE="field1,field2,..,fieldn">

  That's all! For an example, look at http://www.wahyan.edu.hk/interest/submit.html For more options please refer to this file written by the original author.

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• Current Date and Time

  This CGI program returns, when execute, a new HTML document which simply contains the current date and time as they are on IOHK's server.

  To invoke the program, you could either make reference to it using a link:

  <A HREF="http://www.iohk.com/cgi-bin/date">

  or by running it from a FORM:

  <FORM ACTION="http://www.iohk.com/cgi-bin/date">
  <INPUT TYPE="submit" VALUE="Press for time?">
  </FORM>

  Below is an example:

  A real-life example could be found at http://www.iohk.com/UserPages/lcchong/utility.htm

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• Calendar

  This CGI program returns a new HTML document which contains a calendar of a certain month that you specify. You may invoke the program in your home-page by calling:

  <A HREF="http://www.iohk.com/cgi-bin/calendar>

  it will then show you a default page which allows you to enter the calendar you want to show. An example could be found at http://www.iohk.com/UserPages/lcchong/utility.html.

  Alternatively, you may specify the month you wish to show as a parameter to the program:

  <A HREF="http://www.iohk.com/cgi-bin/calendar?month+year>

  Example: This is the calendar of July 1997

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• Finger Gateway

  This CGI program helps you query the FINGER server of IOHK and displays the result to you as a separate HTML document. You may invoke the program by calling the following in your home-page:

  <A HREF="http://www.iohk.com/cgi-bin/finger>

  in which case a default page will be shown in which you could enter the username you wish to FINGER.

  you could also pass the query string to the program directly:

  <A HREF="http://www.iohk.com/cgi-bin/finger?username@host.domain>

  Example: Wish to know more about me?

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No. Technically it is possible but for security reasons, IOHK's Web server is so configured that only scripts/programs located in a specific directory (which happens to be /cgi-bin in our case) could be launched from a Web Page.

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Yes, you may. You are welcomed to submit CGI scripts/programs, that you think are useful, to the Webmaster of IOHK's Web Server for scrutinization. Our WebMaster will consider implementing the requested scripts/programs in IOHK's cgi-bin directory as long as they satisfy the following criteria:

• won't take up too much resource on the server as to affect other users or other services of the server
• do not pose any security risk
• are potentially useful to other users of IOHK

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• NCSA's CGI documentation
• CGI specification
• CGI Programmer's Reference
• Yahoo's CGI Resource Page
• UseNet Newsgroup on CGI

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This question is included for completeness sake. If you do wish to find out more about the author of this FAQ, take a look at his home-page. You may also bug him with questions on CGI or other Web-authoring related questions by email.

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