Re: Exit code for NCL errors

Okay, I found a partial solution that may be useful. This uses the
behavior of code blocks defined by "begin" and "end" statements.
Apparently, many kinds of statement errors halt execution within the
block, but resume execution following the "end" statement. The
documentation for begin/end should be updated to explain this.

So you can catch anonymous fatal errors in main programs, with
strategic placement of the exit and status_exit statements, like this:

begin
   x = new (3, float)
   x(4) = 5 ; cause subscript error
   exit ; normal termination, shell exit code = 0
end
status_exit (1) ; abnormal termination, shell exit code = 1

This is a fairly good solution because it does not need tricky
external code in the shell wrapper to detect whether the program
executed normally. However, apparently this method does not catch
errors within NCL functions. For example, this very common "file not
found" situation will print an NCL fatal error message, but fail to
jump to the status_exit statement:

begin
   f = addfile ("does-not-exist.nc","r")
   exit
end
status_exit (1)

Of course there are ways to add code to detect this particular error
under program control, but that is not the point. Better detection of
unanticipated errors will be helpful when trying to use NCL within
shell scripts. Thanks again for your consideration.

--Dave

On Sun, Aug 5, 2012 at 2:35 PM, Dave Allured <dave.allured@noaa.gov> wrote:
> NCL support team,
>
> Please implement an exit code to the shell indicating failure, when
> NCL terminates abnormally. Even a partial implementation for some
> common errors, such as syntax error, subscript out of range, and file
> not found, would be helpful. Thank you.
>
> --Dave
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Received on Sun Aug 5 16:09:32 2012