ERROR Keyword

ERROR string-expression

Raises a runtime error.

• Sets the built-in variables ERR$ (to the message) and ERR (to 1) when:
  • the error is raised inside an EVAL, or
  • an error handler has been installed with ON ERROR.
• If no handler is installed and you are not inside EVAL, the program terminates.

Remarks

ERR and ERR$ are described on the

Variable Types page.

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Examples

Uncaught error (program terminates)

PRINT "About to fail..."
ERROR "there are owls loose"
PRINT "This line is never reached"

Caught error with ON ERROR PROC...

ON ERROR PROCerr_handler
 
PRINT "Doing a risky thing..."
ERROR "there are owls loose"
PRINT "Carrying on after handler"
 
END
 
DEF PROCerr_handler
    PRINT "ERROR: "; ERR$
    PRINT "ERR code: "; ERR
ENDPROC

In this example, the handler runs, ERR$ contains the message, and ERR is 1.

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Notes

• ERROR accepts a string expression; use it to describe the failure clearly.
• ON ERROR supports only ON ERROR PROCname and ON ERROR OFF.
• When raised inside EVAL, ERR and ERR$ are set; see the EVAL page for how control returns to the caller.

See also:
ON ERROR · EVAL · Builtin Variables