LIST_EXITS

This configuration variable defines a list of file names that can be activated as list exits through the Exit list header keyword. Any suffixes (CMD for Windows, for example) should not be included. List exits are not available under LISTSERV Lite.

An "exit" is a program supplied by the customer to modify the behavior of a product (such as LISTSERV) in ways that the supplier of the product could not anticipate or could not afford to support via standard commands or options. The product checks for the presence of the "exit" program and calls it on a number of occasions, called "exit points". In some cases, the "exit" program supplies an answer ("return code") to the main program, which adjusts its behavior accordingly. For instance, LISTSERV may ask an exit program "Is it OK to add JOE@XYZ.EDU to the ABC-L list?", and the program will answer yes or no, and possibly send a message to the user explaining why his subscription was accepted or rejected. In other cases, the "exit point" call is purely informative; the exit program gets a chance to do something, such as sending an informational message to a user but does not return any answer. Because this "exit" is a computer program, it must be prepared by a technical person and installed by the LISTSERV maintainer.

List "exits" are available to control the major events associated with list maintenance. This makes it easier to tailor the behavior of LISTSERV to local requirements that are too specific to be addressed through standard facilities.

An exit is enabled by adding "Exit= filename" to the list header. For security reasons, all exits must be explicitly declared in the LIST_EXITS configuration variable (in the LISTSERV configuration). This prevents list owners from causing the invocation of arbitrary executable files through the use of the Exit keyword.

For more information, see: LISTSERV Advanced Topics Manual.

The default value is an empty string (no exits enabled).