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ON_ERROR

Syntax | Arguments | Keywords | Example | Version History | See Also

The ON_ERROR procedure determines the action taken when an error is detected inside an IDL user procedure or function by setting state information applying to the current routine and all nested routines. If an override exists within the nested routine, it takes precedence over the ON_ERROR call. ON_ERROR determines the action when no error handlers established with the CATCH procedure are found.

Syntax

ON_ERROR, N

Arguments

N

An integer that specifies the action to take. Valid values for N are:

0
Stop immediately at the statement in the context of the procedure or function that caused the error. This is the default action.
1
Return to the main program level and stop.
2
Return to the caller of the program unit that called ON_ERROR and stop.
3
Return to the program unit that called ON_ERROR and stop.

Keywords

None.

Example

One useful option is to use ON_ERROR to cause control to be returned to the caller of a procedure in the event of an error. The statement: 

ON_ERROR, 2

placed at the beginning of a procedure will have this effect. Include this statement in library procedures and other routines that will be used by others once the routines have been debugged. This form of error recovery makes debugging a routine difficult because the routine is exited as soon as an error occurs; therefore, it should be added once the code is completely tested.


Note
Error handlers established by CATCH supersede calls to ON_ERROR made in the same procedure.

Version History

Original
Introduced

See Also

CATCH, MESSAGE, ON_IOERROR, and Debugging and Error-Handling.

  IDL Online Help (March 06, 2007)