EE 2305

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EE 2305

• Perl CGI Script, Part 3

SMU School of Engineering
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OutlineIn this session, youll get up to
speed for completing your Website (Chapter
references are from Castro)

• Review of the param function (Chapter 9)
• Collecting info from one client page and sending
  it to another client page (Ch. 16)
• Writing client data to a server file (Ch. 19)
• Confirming an order via e-mail (Ch. 19)
• Other capabilities that you may need to complete
  your site.

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Review FORM Tag Attributes

• NAME provides a character string that serves as
  an object name for the form
• ACTION gives the URL location of the CGI (Common
  Gateway Interface) program for submitting data
  collected on the form
• METHOD specifies the method used to move the data
  on the form from the client to the server. "get"
  causes the form data to be appended to the end of
  the URL

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Parsing Input from Links or Forms(Review from
2nd PerlCGI Presentation)

• When a user submits a link or form, the
  name-value pairs are transferred in one long
  stream. When the get method is used, these are
  appended to the URL and sent to the cgi file
  specified in the ACTION parameter
• To be useful, the stream must be parsed into
  intelligible chunks
• Use the built-in PerlCGI function param to
  extract information.

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Using param

• To get the scalar value of a single variable from
  the submitted form, use the code shown on p. 104.
• To get the array value of multiple variables from
  the submitted form, use the code on p. 105.
• Note pp. 106-107 if you want to do more in one
  step.
• Note that the print commands in the examples
  are only for use in debugging.

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Collecting info from one page and sending it to
another page (Chapter 16)

• Remember that Perl is operating in the server,
  and until the user clicks on the shopping cart
  link, the HTML file for the cart is also still in
  the server.
• This fact is important for understanding the
  tricks you are about to learn.
• Chapter 16 shows two approaches. We will use the
  Hidden Field approach because it is easier than
  Cookies, and some users may not have Cookies
  enabled in their browser.

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Using Hidden Fields in a Form

• Read p. 206
• Practice making hidden fields in a form so that
  you get the idea, using the example on p. 207.
  Remember that the value of the ACTION parameter
  is whatever name you give to your CGI file in the
  browser. It must have a .cgi extension. You
  dont have to put it in a cgi-bin on SMU servers,
  but you do have to put it in your public_html
  directory.
• Remember to use the get METHOD.

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Storing the collected data in the Hidden Field

• Read pp. 208-209.
• Note that two scripts are required. One is for
  processing the form that is submitted by the user
  and setting up the hidden fields. Then you need a
  second script for storing the collected data into
  the hidden fields.
• Study the captions in Figures 16.2-16.6.
• Note that the names of the files in 16.3 and 16.5
  are hidden1.cgi and hidden2.cgi, respectively.
  This is crucial for getting the transfer from one
  web page to another.

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Writing Client Data to a Server File

• After you have captured information about the
  user, his order, and his credit card , you need
  to write this info to a file. See pp. 248-254.
• Note that the filehandle is a simple way to
  refer to the file.
• Also, if the file is in your public_html
  directory, you dont need the full path name.
• The flock function is needed in a real e-commerce
  situation, to allow only one user at a time into
  a file.

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Confirming a user order via E-mail

• Pp. 265-6 show how to generate e-mail to your
  customer from within the server.
• The sendmail program in SMUs server is located
  at usr/lib/sendmail
• Obviously, the users e-mail address must be one
  of the input items in the client.

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Miscellaneous Items

• The following several slides may be useful to
  you, depending on the kinds of things you are
  doing on your website

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Putting stuff into your HTML from the server

• The scripts in Castros book all have print
  statements at the end, which are there to help
  you test the functioning of the script.
• In most cases, these need to be removed from your
  program after you have tested it.

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Review from Perl CGI, Part 1

• The primary way to get output from the server
  back to the client is via the PERL print command
• !/usr/local/bin/perl
• The following script causes "Stuff" to appear
  on the screen.
• print "Content-type text/html\n\n"
• print "Stuff"

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Formatting Output to the Client HTML

• After processing is done, and the Content-type
  line is entered,
• Type print
• Type "
• Type ltTAGgt (the name of the HTML tag you want to
  send to the browser)
• Type the data variables
• Type the closing tag lt/TAGgt"

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Note

• To send a symbol to the client browser, that is
  also used in PERL, such as quote, semi-colon,
  ampersand, etc., place a backslash \ in front of
  it to prevent the PERL processor for getting
  confused
• Although the ltBRgt tag may be used to create a new
  line in the browsers mark-up, and \r was used in
  JavaScript to force a new line in markup, use \n
  in your CGI script to cause a new line in the
  HTML (page source) to make it easier to read

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To Print Several HTML Lines at Once

• This is a special Perl CGI shortcut
• print ltlt"some label
• Then type as many HTML lines as you wish.
• \n not needed. Just remember to \ in front of
• When you are ready to end the HTML
• some label

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Simplifying Paths to Images Links

• HTML generated by Perl CGI Scripts is not
  actually in your public_html folder
• To avoid having to use absolute paths for these
• HTML has a ltBASEgt tag which can be used to tell
  the browser which folder you want to pretend the
  files are in. Inside the ltHEADgt of the HTML,
  print the Perl CGI
• print "ltBASE HREF\"HTTP//www.engr \"gt"

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Outputting a Hash as a Table

• Type print "ltTABLEgt\n" with attributes
• If table headers are desired print
  "ltTRgtltTHgtKeylt/THgtltTHgtValuelt/THgtlt/TRgt"
• Type foreach key (keys hashname)
• Type print "ltTDgtkeylt/TDgt" prints 1st column
• Type print "ltTDgthashnamekeylt/TDgt" prints 2nd
• Type (completes foreach loop)
• Type print "lt/TABLEgt"

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Outputting an Array as a List

• Type print "ltOL gt\n" (or ltULgt)
• Type foreach item(_at_arrayname)
• Type print "ltLIgtitem\n"
• Type (completes foreach loop)
• Complete the list definition
• print "lt/OLgt" (or lt/ULgt)

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Formatting Dollars Cents

• Type printf("\.2f",yourdata) (formats the
  number to 2 decimal places for cents)
• To pad integers with leading spaces type
• printf("m.nd",yourdata)
• m is the total number of spaces and digits
• n is the number of digits

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Term Project

• Be sure to note the Term Project grading criteria
  at http//www.engr.smu.edu/ee/2305
• Using Perl CGI Script to Capture user input and
  provide a summary back is important, but much of
  the material covered in these three sessions is
  not absolutely necessary. Its embellishment.
• Also, remember that these three sessions are
  provided only for the term project they will not
  be on the Lecture test or final exam

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