Function: condition-case

condition-case is a special form defined in eval.c.

Signature

(condition-case VAR BODYFORM &rest HANDLERS)

Documentation

Regain control when an error is signaled.

Executes BODYFORM and returns its value if no error happens. Each element of HANDLERS looks like (CONDITION-NAME BODY...) or (:success BODY...), where the BODY is made of Lisp expressions.

A handler is applicable to an error if CONDITION-NAME is one of the error's condition names. Handlers may also apply when non-error symbols are signaled (e.g., quit). A CONDITION-NAME of t applies to any symbol, including non-error symbols. If multiple handlers are applicable, only the first one runs.

The car of a handler may be a list of condition names instead of a single condition name; then it handles all of them. If the special condition name debug is present in this list, it allows another condition in the list to run the debugger if debug-on-error and the other usual mechanisms say it should (otherwise, condition-case suppresses the debugger).

When a handler handles an error, control returns to the condition-case and it executes the handler's BODY... with VAR bound to (ERROR-SYMBOL . SIGNAL-DATA) from the error.
(If VAR is nil, the handler can't access that information.)
Then the value of the last BODY form is returned from the condition-case expression.

The special handler (:success BODY...) is invoked if BODYFORM terminated without signaling an error. BODY is then evaluated with VAR bound to the value returned by BODYFORM.

See also the function signal for more info.

View in manual

Probably introduced at or before Emacs version 17.

Source Code

// Defined in /usr/src/emacs/src/eval.c
{
  Lisp_Object var = XCAR (args);
  Lisp_Object bodyform = XCAR (XCDR (args));
  Lisp_Object handlers = XCDR (XCDR (args));

  return internal_lisp_condition_case (var, bodyform, handlers);
}