try

Advanced exception handling with multiple handlers. Feather's try implementation is fully compatible with TCL 8.6+.

Syntax

try body ?handler...? ?finally script?

Where handlers can be:

• on code varList script - matches specific return codes
• trap pattern varList script - matches error codes by prefix

Parameters

• body: The script to execute
• on code varList script: Handle specific return code
• trap pattern varList script: Handle errors matching errorcode pattern
• finally script: Script that always executes (regardless of body/handler outcome)

Return Codes

The on handler matches these completion codes:

Code	Name	Meaning
0	ok	Normal completion
1	error	Error occurred
2	return	return command
3	break	break command
4	continue	continue command

Integer code values are also supported.

Trap Pattern Matching

The trap handler matches errors by -errorcode prefix:

• Empty pattern {} matches all errors
• Pattern {A B} matches errorcode {A B} or {A B C} (prefix matching)
• First matching handler is selected; on error will mask subsequent trap handlers

Handler Variables

The varList can be:

• Empty: no variables bound
• One variable: receives the result or error message
• Two variables: receives result and options dictionary

Use - as script to fall through to next handler. The first matching handler's varList is used for variable binding.

Finally Clause

• Always executed regardless of body/handler outcome
• If finally raises an error, it overrides previous result
• Otherwise, preserves the result from body or handler

Exception Context

If an exception occurs during a handler or finally clause, the original exception's status dictionary is added to the new exception under the -during key. This preserves context about what exception was being handled when the new error occurred.

Examples

Output

Output

See Also

• catch
• throw
• error