Class 27: More Forms and CGI

Held Tuesday, October 10, 2000

Summary

Today we continue our investigation of CGI by writing some CGI scripts that take input from a form.

Notes

• Today's lab: More CGI
• Thursday's convocation: Will Talbert, Noyce Visiting Professor speaks on Studying the Origin of the Elements Using Radioactive Ion Beams. 11:00 in Harris.
  • Why do they put Physicists in Harris?
  • Extra credit on the next exam for attending
• This past weekend, I went to a marriage celebration for folks I knew in college (at the University of Chicago, another liberal arts institution). Almost everyone I know went into "IT" (even though they were economics, history, philosophy, ... majors).
• Don't forget that your sample 10 entries for Vivek's Dating Service are due now.

Overview

CGI Scripts, Revisited

• Basic pattern of information flow.
  • Browser requests a page.
  • Server looks at suffix.
  • If the suffix is .cgi, runs a program. Otherwise, generally just returns a file.
• The CGI programs we write are calls to Scheme programs which generate HTML.

Extending Information Flow

• The browser can also add information when it requests a page.
• Typically, the information takes the form of a name and an associated value.
  • E.g., I'm looking for a course whose number is CSC151.
• Each language provides its own way of accessing those values.
• In Scheme, you typically write something like

  (extract-binding/single 'name (get-bindings))
  

• To make the forms used to supply information, you use special HTML.