| catch |
|
grammar |
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A statement, used in conjunction with the
try
statement, that provides control over error handling.
When an error occurs in the block associated with a
try
statement, control passes to the associated
catch
block and information about the error is stored in a dictionary that can
be referenced by
name
in the
catch
block.
A
catch
block that returns a zero value (i.e.,
FALSE)
is asking the interpreter to continue with its normal error handling,
which includes writing an error message on standard error.
In all other cases (i.e., a non-zero or missing return value) error handling is
short-circuited, the error message is suppressed, and execution continues at the
statement that immediately follows the try/catch block.
Its usage description can be summarized as follows:
Statement:
try Compound catch ( name ) Compound
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| Example: |
The following script demonstrates the effect of the return value in a
catch statement.
import yoix.stdio.*;
printf("Test #1:\n");
try {
vbl; // undefined
}
catch(error) {
printf("Message #1: %s\n", error.message);
return(FALSE); // allows system error message
}
printf("Test #2:\n");
try {
vbl; // still undefined
}
catch(error) {
printf("Message #2: %s\n", error.message);
// no return statement suppress system error message
}
printf("Test #3:\n");
try {
vbl; // still undefined
}
catch(error) {
printf("Message #3: %s\n", error.message);
return(TRUE); // suppress system error message
}
printf("Testing completed.\n");
The results on standard output would look something like:
Test #1:
Message #1: Error: undefined; Name: vbl; Line: 5; Source: /tmp/xxx
Error: undefined; Name: vbl; Line: 5; Source: /tmp/xxx
Test #2:
Message #2: Error: undefined; Name: vbl; Line: 13; Source: /tmp/xxx
Test #3:
Message #3: Error: undefined; Name: vbl; Line: 21; Source: /tmp/xxx
Testing completed.
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| See Also: |
reference,
try
|
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