Can we add an error state variable?

[Ethan A M. <merritt@u.washington.edu>]

The following query, and my response to it, appeared on the newsgroup:

>>I am already using with success gnuplot and batch mode operation. The
>>problem I am facing is how to understand if a plot was not performed
>>correctly, when run as a batch job.
>>
>>I.e. when I issue this command "plot sin(x" I get a "')' expected"
>>error, or when I give "plot ssin(x)" I get error "undefined function:
>>ssin".
>>
>>Is there a safe way to grab all these errors? Something like a "return
>>value" ?

>No return value, sorry.
>The closest I can think of is illustrated below
>ierr = 1
>plot sin(x     ; ierr=0
>print (ierr == 1) ? "failed" : "success"

I am wondering if we can and should implement something of the sort
automatically.  It's easy to have int_error() set an error flag.
The question is whether there is a single place, or a small number of
places, where such a flag can be guaranteed to be reset before the
next command is executed, yet leaves it available for testing?

Alternatively we could allow the user to define an asynchronous
error-handling function, and call it from int_error() if it exists.
E.g.:

#define error handler routine (must have this name)
user_error_handler(x) = (saw_error = x)

saw_error = 0
[some series of commands]
print (saw_error != 0) ? "some error happened" : "OK"






Any ideas?

-- 
Ethan A Merritt