The GT.M exception trapping allows you to do the following:
DO a recovery routine and resume the original command stream.
GOTO any special handling; an extended ZGOTO provides for context management.
Report an error and enter Direct Mode for debugging.
OPEN Input/Output devices with specific traps in addition to the main trap.
Trap and process an exception based on a device error.
Trap and process an exception based on terminal input.
The following table summarizes the GT.M language extensions that facilitate exception handling.
|
GT.M Exception Handling Extensions | |
|---|---|
|
EXTENSION |
EXPLANATION |
|
ZGoto |
Removes zero or more levels from the M Invocation stack and, optionally, transfers control. |
|
ZMessage |
Signals the specified condition. |
|
$ZCSTATUS |
Holds the value of the status code for the last compile performed by a ZCOMPILE command. |
|
$ZEOF |
Contains indication of whether the last READ reached end-of-file. |
|
$ZMessage() |
Translates an error condition code into text form. |
|
$ZLevel |
Contains current level of DO/XECUTE nesting. |
|
$ZStatus |
Contains error condition code and location of last exception condition occurring during routine execution. |
|
$ZSYstem |
Contains the status code of the last ZSYSTEM. |
|
$ZTrap |
Contains an XECUTE string or entryref that GT.M invokes upon encountering an exception condition. |
|
EXCEPTION |
Provides a deviceparameter specifying an XECUTE string or entryref that GT.M invokes upon encountering a device-related exception condition. |