package require orphan
set o [Orphan %AUTO% ?-script script?
$o configure -script newscript
$o destroy
The oprhan package provides an object oriented scheme to execute a Tcl script when the process's parent process changes. Normall this happens when the process is orphaned (that is its parent process exited).
When the Orphan object is created, it
captures the parent's process id and uses the after
command to poll for changes in the parent's id every second. The
-script option, used at construction time or
in the configure subcommand provides a script
to execute at the global level when the parent process id changes.
An empty script causes the object to continue to poll, however if the
parent process id changes no script is executed.
This implementation, therefore has a few potential problems:
If the parent changes prior to creating the
Orphan object, no script is called.
If the parent changes while the -script
option value is empty, when -script is
provided, it will never be called.
The limitations above suggest that the best way to use this
facility is to create an Orphan object with
a script early in script execution.