Internet intrarnet CIS class 7
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Internet / Intranet
CIS-536
Class 7
HTML Forms
A Method to Allow Users to Pass Information to a CGI
Script
Forms Allow Information to Be Entered Via:
Text Fields
Selectable Lists
Checkboxes
Radio Buttons
Submit / Reset Buttons
Each Field Is Identified by a Name
Optional Default Value
E.g.
<INPUT TYPE=“Text” Name=“Field1” Value=“Default”>
<INPUT TYPE=“Submit” Value=“Click Here”>
Example
HTML Forms (2)
Submit Button Sends Data to CGI Script
Name/Value Pairs Separated By &
METHOD = “GET”
Uses HTTP Get Method
Parameters are Sent in URL
“Command Line” Arguments
Data Follows “?”
Easily Visible to Users
Some Servers Truncate the URL
Passed to Perl as QUERY_STRING Environment Variable
METHOD = “POST”
Data is Sent in HTTP Message Body
Passed to Perl as stdin
ACTION=“URL”
Identifies the Target URL
ACTION =“mailto:xxx”
Data is Mailed to Target email Address
Example
Forms – Text Fields
Text Box: Type=Text
Size=“15” Maxlength=“20”>
Size – Size of Text Box in Characters
Maxlength – The Maximum Number of
Characters Allowed
Type=Password
Same, Except User Input is Echoed as *’s
Note: Password is Still Sent to Server in Plain
Text
Pwd Example
Example
Forms – Multiline Text Fields
Multiline Text
Rows=“5” Cols=“30” WRAP=“Virtual”>
Rows, Cols – The Size of the Field in Characters
Note: This Only Controls the Size of the Display Box.
Scroll Bars Allow More Data.
Wrap=Of
No Wrapping. Horizontal Scroll Bar for Additional Text.
Wrap=Virtual, Physical
Wrap Text Based on Number of Columns
Wrap=Virtual –Do Not Send Inserted Carriage Returns
Wrap=Physical – Send Inserted Carriage Returns
Example
Forms – CheckBoxes and Radio
Buttons
Radio Buttons Allow Only One Option to Be
Selected
Checkboxes Allow Multiple Selections
<INPUT Type=“CheckBox” Name=“CB1” Value=“A” CHECKED>Pick1
<INPUT Type=“CheckBox” Name=“CB1” Value=“B”> Pick2
Name - Identifies the Grouping.
Value – The Value Passed to the Server if This Item is Selected.
For Multiple Selections, Values are Concatenated
CHECKED – Indicates the Default Status is Checked
Examples:
If the User Checks Pick1:
Sent to Server: CB1=A
If the User Checks Pick1 and Pick2:
Sent to Server: CB1=AB
Example
Forms – List Boxes
<SELECT Name=“LBox” Size=“5” Multiple=“5”>
<OPTION Value=“Choice1” >First Choice
<OPTION> Second Choice
</SELECT>
Size – The Number of Rows to Display
Access Additional Rows Via Scroll Bar
Size=1 Creates a Drop-Down List
Multiple – The Maximum Number of Items That Can Be
Selected From List
Values are Concatenated When Sent to Server
Value – If Specified, This is Sent to Server When Row is
Selected
Unspecified – Text in Row is Sent to Server as the Value
Example
Forms – Submit and Reset Buttons
Submit
<INPUT type=“submit” value=“press here to submit”>
Reset
<INPUT type=“reset” value=“press here to reset”>
Sets all Fields to Their Default Values
Example
Forms –Uploading Files
Allows a User to Upload Contents of a File Instead of Text
<INPUT Type=“File” Name=“FileField”>
Browser Displays a Text Field and a Browse Button to
Allow User to Select a File
If the Form has ENCTYPE=“multipart/form-data”
Contents of File Are Uploaded in This Field
Else
The Filename is Uploaded in This Field
BE CAREFUL!
Can Be a Security Hole if Uploaded Files are Stored in Web
Accessible Directories
Accidentally Selecting a Large File Can Afect Performance
Example
Forms – Hidden Fields
Allows You to Create “Variables”
Passed to Server as if Entered By User
Not Displayed to User in Form
Fully Visible in the HTML
Therefore, Not For Sensitive Info (e.g. Passwords)
Value=“Myval”>
Example
Forms – Image Maps
SRC=“button.jpg”>
Similar to a Submit Button
Graphic is Displayed as Button
Also Passes the Coordinates Where User Clicks
Server Can Process Coordinates
(Server Side Image Maps)
Example
HTML Extensions for Forms
“Tool Tips”
TITLE Attribute on Form Tags
Label Associated With Form Entry
User Can Click On Label to Select Entry Field
<LABEL FOR=“TextID”>Enter Name: </LABEL>
<INPUT TYPE=“Text” ID=“TextID” Name=“Tname”>
Shortcuts
Alt-Character selects Entry Field
ACCESSKEY=“X”
Tab Order
TABINDEX=3
Negative Number Excludes Field From Tab Order
FieldSet
Groups Controls Together (Outline Box)
<Legend> Adds Text To Outline Box
Example
Document Object Model: Forms
Properties
action – The URL Where Form Will be Submitted
length – The Number of Elements in the Form
method – “Get” or “Post”
name – Name as Specified by Name Attribute
target – If in a Frame, the Target Frame Name
Methods
reset() – Reset the Form
submit() – Submit the Form
Objects
elements[] – Array of input elements in the form.
Events
onReset
onSubmit
Return false to Prevent Submission
Validating Forms Using JavaScript
Example
Server Side Includes
.shtml Extension By Convention
Not Enabled on All Servers
<!--#ssi-directive param=“value” -->
Server Side Include Directives:
echo – print certain variables
DOCUMENT_NAME
DOCUMENT_URI
DATE_LOCAL
DATE_GMT
LAST_MODIFIED
include – Include Another File
fsize, flastmod – File Size, Last Modified Date of a Specified
File
exec – Execute a System Shell Command
cgi – Execute a CGI script
config – Adjust Error, Day/Time Formats
Example
CGI / Scripting
Scripts are Programs Run By the Server
CGI – Common Gateway Interface
Methodology For Server/Script Communication
Can Be Written in Any Language Supported By the Server
UNIX Origins
PERL is Most Common
Script Output is Returned to the Browser
Alternative Methodologies Exist
CGI is the Most Portable
PERL – Practical Extraction and Reporting Language
UNIX Based Scripting Language
Ported to Multiple Platforms
How Does Browser Know to Execute a Program?
Program is in a Script Directory
Typically cgi-bin (Apache)
Or By Extension (e.g. .pl, .cgi)
Scripts Must Have Executable Permissions
Scripting Features
Scripts Can Have Input Parameters
Passed as Part of URL : ? Argument (Query String)
Special Characters Passed as % Ascii Hex Values
Name/Value Pairs : Separated by &
Variable
Passed in HTTP Header
Name/Value Pairs
Method = Post
HTML Forms
Passed in Cookies
Netscape Origins, Now Widely Adopted
Name/Value Pairs Associated With a URL
Stored on Client Computer
Users May Turn of Cookies
Scripts Must Be Aware of How Parameters are Being Passed
Diferent Methodology to Access Each Method
Parameters Also Used to Maintain State Information
Help Track a “Session”
Scripting Issues
Security Concerns
No Limits on What CGI Scripts May Access
Potential to Execute Any System Command
Hacker Can Cause Serious and Unforeseen Problems
Potential to Afect More Than Just Your Web Site
Many ISP’s Limit CGI Capabilities
Performance Concerns
CGI Scripts are Run as a Standalone Process
E.g. Interpreter is Loaded and Initialized Each
Time
Alternative to Posting Forms
Mailto Option
Perl
Why Should I Learn Perl?
S/W Engineers Need to Be Adept at Picking Up New
Languages
Need a “Comfort Level” of Expertise
Ability to Write Basic Code
Ability to View/Modify Existing Code
Ability to Learn More as Needed
Develop Reference “Library”
Develop “Guru” Network
Large Public Archives of Perl Scripts
Perl Basics
Interpreted
Originally Used Primarily By UNIX Sys-Admins
“Public Domain”
The preferred language for CGI Scripts
PERL is Relatively Portable
Activestate ActivePerl (Windows / IIS)
UNIX specific scripts dominate (Uses UNIX O/S Commands)
In Class Exercise
Create a Basic Form
Use action=“mailto: xxx” to mail the form result to
yourself
