Using the interrupt and oninterrupt descriptors

To illustrate the concepts of inheritance and scope of the interrupt and oninterrupt descriptors, the following menu definition files define them with frame descriptors and item descriptors in a menu definition file:

   menu="My First Menu"
   begrow=center
   begcol=30
   interrupt=true
   

   name=Run UNIX System V
   action=unix-system
   

   name="Find Modified Files"
   action=`find $HOME -mtime -7 -print > modfiles`nop
   

   name="Find Executable Files"
   action=`find $HOME -perm -100 -print > execfiles`nop
   

   name="Exit My Application"
   action=exit

Menu.interrupt: an example of interrupt signal handling

When defined among the frame descriptors, the value of interrupt is inherited by all processes initiated in action descriptors anywhere in the menu definition file, unless it is redefined for a particular item or SLK. Thus, if the user selects either the Find Modified Files or Find Executable Files item from this menu, the named process will run till its normal completion. However, the user can interrupt either process because interrupt=true is defined among the frame descriptors for this menu. (Note that output from Find Modified Files is saved in a file named modfiles, and that output from Find Executable Files is saved in a file named execfiles.)

When a user presses the interrupt key, the message Operation interrupted! appears at the bottom of the screen and the process is terminated. This is the default behavior when no other messages or actions have been defined via the oninterrupt descriptor, as is the case in this menu.

You can be more specific about what processes you want users to be able to interrupt and about what you want done when a process is interrupted. For example, you can block the interrupt mechanism for any item on the menu by setting the interrupt descriptor to FALSE for the item. A process initiated from that item cannot be interrupted, even if the frame descriptor interrupt is set to true:

   menu="My First Menu"
   begrow=center
   begcol=30
   interrupt=true
   

   name="Run UNIX System V"
   action=unix-system
   

   name="Find Modified Files"
   action=`find $HOME -mtime -7 -print > modfiles`nop
   interrupt=false
   

   name="Find Executable Files"
   action=`find $HOME -perm -100 -print > execfiles`nop
   oninterrupt=`message Partial output is in execfiles`nop
   

   name="Exit My Application"
   action=exit

Menu.oninterr: a further example of interrupt handling

If a user selects Find Modified Files from this menu definition file, the process it initiates cannot be interrupted. If a user selects Find Executable Files from this menu, it can be interrupted, and when it is, the processing defined for this item by the oninterrupt descriptor will occur.