DEFER INTERRUPT / QUIT
The DEFER
instruction defines the program behavior when interrupt or
quit signals are received.
Syntax
DEFER {
INTERRUPT |
QUIT }
Usage
The DEFER
instruction controls the behavior of the program when an interrupt
signal (SIGINT
) or quit signal (SIGQUIT
) has been received.
DEFER INTERRUPT
and DEFER QUIT
instructions should
only be used in the MAIN
block, to be executed at the beginning of the program.
DEFER INTERRUPT
indicates that the program must continue when it receives an
interrupt signal (SIGINT
. By default, the program stops when receiving an interrupt
signal.
Once deferred, you cannot reset to the default behavior.
When an interrupt signal is caught by the runtime system and DEFER INTERRUPT
is
used, the int_flag
predefined
global variable is set to TRUE
by the runtime system.
Interrupt signals are raised on terminal consoles when the user presses a key like CTRL-C,
depending on the stty configuration. When a program is displayed through a front-end, no terminal
console is used; therefore, users cannot send interrupt signals with the CTRL-C key. To send an
interruption request from the front-end, you must define an action view with the name
'interrupt
'.
DEFER QUIT
indicates that the program must continue when it receives a quit
signal (SIGQUIT
). By default, the program stops when receiving a quit signal.
When a quit signal is caught by the runtime system and DEFER QUIT
is used, the
quit_flag
predefined global
variable is set to TRUE
by the runtime system.