CS3172 > Materials > sysdocs > CGI cookies

J. Blustein

Web-centric Computing

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System Documentation

Notes About Cookie Expiry Times

• Cookies can only have one value at a time (just like a variable in a program)
• Cookies are limited to 4Kb (4096 octets) each.  We can use Perl's pack function to encode lots of data into a string.  (The current Perl documentation should be at the perldoc.perl.org website
• Only the name and value parts are required. The domain, expires, path, and secure parts are optional.
• The expires part must be expressed as GMT and be in this format: Wdy, DD-MMM-YYYY HH:MM:SS GMT

  Wdy is

  the three letter abbreviation for the weekday (Mon, Tue, Wed, Thu, Fri, Sat, Sun).

  DD is

  two digits for the numeric day of the month (e.g., the first of the month would be 01).

  MMM is

  the three letter abbreviation for the month (Jan, Feb, Mar, Apr, May, Jun, Jul, Aug, Sep, Oct, Nov, Dec).

  YYYY is

  the year.

  HH is

  two digits for the hour in twenty-four format (e.g., 10p.m. would be 22, and 5a.m. would be 05).

  MM is

  two digits for the minutes in the hour (e.g., 09).

  SS is

  two digits for the seconds in the minute (e.g., 09).

  For example noon on 25 October 2001 in Greenwich would be Thu, 25-Oct-2001 12:00:00 GMT
• If you use CGI.pm with perl then it can compute expiration times for you with such strings such as

  +ns

  n seconds in the future

  +nm

  n minutes in the future

  +nd

  n days in the future

  +nM

  n months in the future

  +ny

  n years in the future

  now

  immediately

  -nd

  a time in the past (n days ago)

  For example:

  print header( -cookie=>$variable, -expires=>'+1d' ); # tomorrow

  print header( -cookie=>$variable, -expires=>'Thu, 25-Oct-2001 12:00:00 GMT' );

http://www.cs.dal.ca/~jamie/course/CS/3172/Materials/Docs/cgi-advice/CGIpmExpires.html

Version:

18 Feb. 2003

Author:

J. Blustein <jamie@cs.dal.ca>