HP Fortran Programmer's Guide (B3908-90031; September 2011)

Using the ON statement
Trapping +Ctrl-C trap interrupts
Chapter 5138
Trapping +Ctrl-C trap interrupts
A +Ctrl-C interrupt can occur during the following circumstances:
• When the user enters the interrupt code from the terminal while the program is running or awaiting
input
• During the execution of a PAUSE statement
The trap procedure for a +Ctrl-C interrupt must have no formal arguments. The interrupt code is the
character defined by the HP-UX stty(1) command for the intr parameter. The system default for intr is
+Ctrl-C.
You can use the +Ctrl-C form of the ON statement to handle the interrupt signal 2. In the following example,
when an interrupt occurs, the program reports status information on standard output, assuring the user that
the program is still at work in the DO loop. The program uses the ON statement to set the action for a +Ctrl-C
interrupt to be the call to the trap handler status:
PROGRAM main
COMMON i
ON CONTROLC CALL status
DO i = 1, 100000
... ! Long computation
END DO
END
SUBROUTINE status
COMMON i
PRINT *, 'Currently on iteration ', i
END SUBROUTINE status
When this program is run, a +Ctrl-C interrupt causes the status routine to be called, which prints the
iteration count. The program then resumes executing the DO loop.