$Web Expire

<section begin="desc" />Set expiration date/time of Web response<section end="desc" />

$Web_Expire sets the expiration date and time for the Web Server response entity being returned by the application. Using $Web_Expire, you can control how long a browser caches an entity returned by your application.

$Web_Expire requires one argument and returns a numeric status code. It is also callable.

Syntax

<section begin="syntax" />%rc = $Web_Expire( exp_time ) <section end="syntax" />

Syntax terms

exp_time	A date/time expressed in seconds since 12 AM on January 1, 1900. You can use the $Web_Datens function to get the current date in this format, and manipulate it using standard User Language expressions.

Return codes

Code	Meaning
0	Completed successfully
-1	Not a web thread
-4	Invalid datetime value

Examples

Use $Web_Expire to control how long a browser caches an entity returned by your application.

* Get current date in binary %X = $WEB_DATENS * Add one week to the current date %X = %X + 7*24*60*60 * Ensure browser doesn't cache returned data * longer than one week %RC = $Web_Expire( %X ) * Changed my mind, only cache URL for 1 hour. * The previous $Web_Expire call is forgotten. %X = %X - (7*24-1)*60*60 %RC = $Web_Expire( %X )

In the above example, $Web_Expire is called to set the expiration date for the response entity. A second $Web_Expire demonstrates that you can override the $Web_Expire value any time you wish.

See also

• $Web_Last_Modified
• "Understanding browser caching"