cs-142:cgi [CS Wiki]

This is a brief tutorial on how to create web pages that call your code. It is possible to have the web page call your C++ code, but we are going to use another language that is like C++ in order to make this tutorial more simple.

First we need to talk about how a web server works. It takes the Universal Resource Locator (URL) that you type into your browser and can convert it into a folder and file structure. All of you have a folder on a web server in the Computer Science Department that you can put things into so they can be seen on the web server.

On the lab computers you can go to Start/Computer/username(//samba1(F:) to access this folder. Open this folder and go to the public_html folder. This is where the web server will look when you enter a URL like

http://students.cs.byu.edu/~username

You can also access these files from a macintosh by opening a terminal window and then “ssh schizo.cs.byu.edu”.

You can create files in this folder that will be seen on the web server. Open notepad and enter the following: <syntaxhighlight lang=“html4strict”> Hello World </syntaxhighlight>

Save this file as text in F:\public_html\hello.html

You should now be able to see it at

http://students.cs.byu.edu/~username/hello.html

If you have never written html pages before, you can find a good tutorial at http://www.w3schools.com/ w3schools. But you would really like to have code executed when you enter a URL. In order to do this, you need to write a form and a CGI script that will be executed when you press the submit button on that form.

Open notepad and enter the following:

<html>
<form method="post" action="name.cgi" enctype="multipart/form-data">
 
What's your name?
<input type="text" name="name"  />
<p>
What's your favorite color?
<select name="color" >
<option value="red">red</option>
<option value="green">green</option>
<option value="blue">blue</option>
<option value="chartreuse">chartreuse</option>
</select>
<input type="submit" name=".submit" />
</form>
</html>

This will create a form that will let you enter your name and your favorite color. When you press the submit button, it will call the cgi script “name.cgi” that we will write next.

Save this file as text in F:\public_html\form.html

Now you want to write code that will be executed when you click on the submit button.

Open notepad and enter the following:

#!/usr/bin/perl
 
use strict;
use CGI qw/:standard/;
print header;
print start_html('Simple Script');
if (param) {
  print "Your name is ",param('name')," ";
  print "Your favorite color is ",param('color'),"<p>";
}
print end_html;

Save this file as text in F:\public_html\name.cgi

This program is written in a language called http://www.perltutorial.org/ perl

It is a lot like C++ and you should be able to pick it up easily and write code that will run from a web page.

cs-142/cgi.txt · Last modified: 2015/01/07 09:16 by ryancha

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