Tracking Users Using WML

March 27, 2003
By Steve Schafer

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Setting a Cookie with Perl

As discussed earlier, we can use the HTTP header Set-Cookie to set cookies. In its simplest usage, this header takes the following form:

Set-Cookie: <name of cookie>=<value of cookie>

For example, a real header might be as follows:

Set-Cookie: name=Steve

When this header is passed to a browser, it sets the cookie "name" equal to "Steve." Because the header doesn't include a time to live (TTL), the cookie is only valid for the current session. When the browser is closed, the cookie expires and is deleted.

To include a TTL, you add the parameter expires as shown in the following example:

Set-Cookie: name=Steve; expires=Monday, 24-Mar-03 23:59:59 GMT

Notice the use of a semicolon (;) to delimit the parameters. The date is in the format "weekday, dd/Mon/yy hh:mm:ss." In the example above, the cookie will expire at one second before midnight on Monday, March 24, 2003, Greenwich Mean Time.

Tip: It's important to include at least one blank line after the Set-Cookie header and before the WML headers so the client correctly identifies the WML headers.

Let's look at a real example of using Perl to set a cookie for a WML deck. The following code snippet shows how Perl is used to set a cookie and output a status ("Cookie set") message:

#!/usr/bin/perl# Define minimal deck$deck = '<wml>  <card>    <p>      Cookie set.    </p>  </card></wml>';# Send Content-type and Set-Cookie headersprint "Content-type: text/vnd.wap.wml \n";print "Set-Cookie: name=Steve \n";# Send WML header infoprint "\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 deckprint $deck;

The cookie in the code above was set without a TTL. To set an expiration date, we draw on the Date::Calc module to do our date calculations:

#!/usr/bin/perl# Include Date::Calc.use Date::Calc':all';# Get today in GMT($year,$month,$day) = Today([$gmt]);# Add 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";# Define deck$deck = '<wml>  <card>    <p>      Cookie set.    </p>  </card></wml>';# Send Content-type and Set-Cookie headersprint "Content-type: text/vnd.wap.wml \n";print "Set-Cookie: name=Steve; expires=$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;

Note: The Date::Calc module has been covered in several previous articles. The module is available from CPAN, at http://search.cpan.org/author/STBEY/Date-Calc-5.3/Calc.pod.

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