Tracking Users Using WML

Reading Cookies with Perl

Reading cookies with Perl is even easier than setting them, thanks to the environment variable HTTP_COOKIE. This variable contains name/value pairs for all applicable cookies (those matching the current scope).

To parse the name/value list, you could use the following code:

@nvpairs=split(/[,;] */, $ENV{'HTTP_COOKIE'});foreach $pair (@nvpairs) {   ($name, $value) = split(/=/, $pair);   $cookie{$name} = $value;}

This code effectively parses the cookie list into the array $cookie, where each value can be accessed by its name. For example, our earlier "name" example would yield:

$cookie{'name'} = "Steve"

An extended example, displaying the cookie value in WML, is shown below:

#!/usr/bin/perl# Break cookies into name/value pairs# and store into cookie array@nvpairs=split(/[,;] */, $ENV{'HTTP_COOKIE'});foreach $pair (@nvpairs) {   ($name, $value) = split(/=/, $pair);   $cookie{$name} = $value;}# Define WML deck$deck = '<wml>  <card>    <p>      Cookie (name) = '.$cookie{'name'}.'    </p>  </card></wml>';# Send Content-type and Set-Cookie headersprint "Content-type: text/vnd.wap.wml \n";print "Set-Cookie: name=Steve; expires=$date; \n";# Send WML headersprint "\n<?xml version=\"1.0\"?>\n";print "<!DOCTYPE wml PUBLIC \"-//WAPFORUM//DTD WML 1.1//EN\""   . " \"http://www.wapforum.org/DTD/wml_1.1.xml\">\n";# Send the deckprint $deck;

If the cookie was still set, this code would display the following:

Cookie (name) = Steve

Deleting Cookies

To remove a cookie, you simply set the expiration of the cookie to a date/time that has already passed. For example, we could use the code earlier but subtract a day or two to expire the cookie. The code, using Date::Calc functions, would resemble the following:

# Get today in GMT($year,$month,$day) = Today([$gmt]);# Subtract a year (365 days)($year,$month,$day) =  Add_Delta_Days($year,$month,$day,"-365");# Get textual representations of month and day of week$dow =  Day_of_Week_to_Text(Day_of_Week($year,$month,$day));$month = Month_to_Text($month);# Make sure day is two digitsif ($day<10){ $day = '0'.$day;}# Assemble expiration date$date = $dow.", ".$day."-".$month."-".$year." 23:59:59 GMT";

Note the use of a minus sign in the Add_Delta_Days function to subtract a year from today. We could just as easily subtract only one day.

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This article was originally published on March 27, 2003