LASTERR

Description

LASTERR is a read-only pseudo variable. Any write attempt results in an error. LASTERR is somewhat like a volatile status value that is used by many functions to report success or error. Most functions and commands set LASTERR to 0 (ERR_OK) on entry. When the Scripting Language detects inconsitencies, LASTERR is set to a value other than 0 to report the problem to the program.

The system defines the following error codes:

Example

This program demonstrates LASTERR. On startup, LASTERR is always 0 (ERR_OK). Variable assignments don't affect LASTERR, so the first program line reads LASTERR and keeps its old value. In the 4.th line, there's a faulty instruction, which sets LASTERR to 4 (ERR_ARGUMENT). The PRINT statement after that resets LASTERR to 0 again.

let a = LASTERR
outmode -2
print a
open "x", 999, "..."
let b = LASTERR
print b
print LASTERR
end

Remarks

Because LASTERR is only valid immediatly after command execution, it needs immediate evaluation or must be stored into a variable for later evaluation.