Defines the default courses of action  when  a  command  or  program
  executed   within  a  command  procedure  (1)  encounters  an  error
  condition or (2) is interrupted by CTRL/Y.   The  specified  actions
  are  taken  only  if  the  command  interpreter is enabled for error
  checking or CTRL/Y interrupts; these  are  the  default  conditions.
  You can use the ON command only within a command procedure.

  Format:


    ON  condition THEN [$] command

Additional information available:

ParametersExamples

 condition

  Specifies either  the  severity  level  of  an  error  or  a  CTRL/Y
  interrupt.   To  specify  the severity level of an error, use one of
  the following keywords:

       WARNING
       ERROR
       SEVERE_ERROR

  You can truncate any of these keywords to one  or  more  characters.
  The default error condition is ON ERROR THEN EXIT.

  To specify a CTRL/Y interrupt, use the following keyword:

       CONTROL_Y

 command

  Specifies the action to be taken.  You can specify any valid command
  line  after the keyword THEN; you can optionally precede the command
  line with a dollar sign ($).

  If you specified an error condition as the condition parameter,  the
  action  is  taken when errors equal to or greater than the specified
  level of error occur.

  1.   $ ON SEVERE_ERROR THEN CONTINUE

  After this statement is executed in  a  command  procedure,  when  a
  warning or an error occurs the procedure continues normally.  When a
  severe error occurs, the ON statement  instructs  the  procedure  to
  continue  with  the  next  statement anyway.  Once the statement has
  been executed as a result of a fatal error  condition,  the  default
  action (ON ERROR THEN EXIT) is reinstated.

  2.   $ ON ERROR THEN GOTO BYPASS
       $ RUN A
       $ RUN B
          .
          .
          .

       $ EXIT
       $ BYPASS:
       $      RUN C

  If either program A or program  B  returns  a  status  code  with  a
  severity  level  of error or severe error, control is transferred to
  the statement labeled BYPASS and program C is run.

  3.   $ ON WARNING THEN EXIT
          .
          .
          .

       $ SET NOON
       $ RUN [SSTEST]LIBRA
       $ SET ON
          .
          .
          .

  The ON command requests that the procedure exit  when  any  warning,
  error, or severe error occurs.  Later, the SET NOON command disables
  error checking before executing the RUN command.  Regardless of  any
  status  code  returned  by  the  program  LIBRA.EXE,  the  procedure
  continues.  The next command, SET ON, reenables error  checking  and
  reestablishes the most recent ON condition.