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Rexx has the ability to also work on Error handling as in other programming languages.
The following are some of the various error conditions that are seen in Rexx.
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ERROR − This even is raised whenever a command which is sent to the operating system results in an error.
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FAILURE − This even is raised whenever a command which is sent to the operating system results in a failure.
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HALT − This is normally raised whenever an operation is dependent on another operation. An example is if an I/O operation is being halted for any reason.
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NOVALUE − This event is raised when a value has not been assigned to a variable.
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NOTREADY − This is raised by any I/O device which is not ready to accept any operation.
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SYNTAX − This event is raised if there is any syntax error in the code.
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LOSTDIGITS − This event is raised when an arithmetic operation results in a loss of digits during the operation.
Trapping Errors
Errors are trapped with the help of the signal command. Let’s take a look at the syntax and an example of this.
Syntax
signal on [Errorcondition]
Where,
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Errorcondition − This is the error condition which is given above.
Example
Let’s take a look at an example on this.
/* Main program */ signal on error signal on failure signal on syntax signal on novalue beep(1) signal off error signal off failure signal off syntax signal off novalue exit 0 error: failure: syntax: novalue: say ''An error has occured''
In the above example, we first turn the error signals on. We then add a statement which will result in an error. We then have the error trap label to display a custom error message.
The output of the above program will be as shown below.
An error has occurred.
An example of error codes is shown in the following program.
/* Main program */ signal on error signal on failure signal on syntax signal on novalue beep(1) exit 0 error: failure: syntax: novalue: say ''An error has occured'' say rc say signal
The output of the above program will be as shown below.
An error has occured 40 6
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