[Info-vax] Returning data from Cobol AST routine.

[Jan-Erik Söderholm]

Den 2021-09-21 kl. 15:00, skrev Arne Vajhøj:
> On 9/21/2021 3:15 AM, Jan-Erik Söderholm wrote:
>> Den 2021-09-21 kl. 03:27, skrev Arne Vajhøj:
>>> On 9/20/2021 6:55 PM, Jan-Erik Söderholm wrote:
>>>> I have been looking at the Cobol AST example here:
>>>> http://computer-programming-forum.com/48-cobol/b75d8c5fdd43048e.htm
>>>>
>>>> This does work fine as an example. But what are the options to get
>>>> some data back to the main program (called "x" in the example)
>>>> from the ast program (called "ast_routine" in the example)?
>>>>
>>>> I have tried different versions of global, external and so on, but
>>>> no luck so far. How to get "x" and "ast_routine" to share some data?
>>>> Anything similar to an COMMON area in Fortran?
>>>>
>>>> The idea is to have an AST routine that will read from a mailbox when
>>>> something is written to it. My idea was that the read of the mailbox
>>>> would be using an AST to avoid polling the mailbox.
>>>>
>>>> This is to have a command input to detached processes to get them to
>>>> reload the config, repoen the log file, close and exit and so on.
>>>>
>>>> Are there more options if not everything is done in Cobol?
>>>> We can easily add some C if that helps...
>>>
>>> external works for me.
>>>
>>> identification division.
>>> program-id. x.
>>> environment division.
>>> data division.
>>> working-storage section.
>>> 01  magic-value         pic 9(10)  display external.
> ...
>>> end program x.
>>> identification division.
>>> program-id. ast_routine.
>>> environment division.
>>> data division.
>>> working-storage section.
>>> 01  magic-value         pic s9(10)  display external.
> ...
>>> end program ast_routine.
>>>
>>> $ cobol x
>>> $ link x
>>> $ run x
>>> sleeping for 5 seconds
>>> 000000012C
>>
>> Ah, OK! that will be tested. Hm, is this limited to numeric variables?
>> My test was using a x(3) variable...
> 
> Try it!
> 
> Per documentation then external just moves the variable to a PSECT
> with the same name as the variable to tell the linker to overlay
> them.
> 
> I would expect that to work with any data type.
> 
>> Hm, if this would had been a read-AST on a mailbos instead of a timer,
>> maybe the ast_routine can just awake the main code and the mailbox
>> been read in the main code. The ast_routine could set a variable that
>> just signals the reason fo the wakeup.
> 
> I don't understand the problem.
> 
> If you want the main flow to wait until something is in the mailbox,
> then why not do a blocking read?
> 
> Arne
> 

No, sorry... The main code does other things (the regular business
processing) all the time. I just do not want it to have to poll the
mailbox with some fixed interval. I expect an AST to be faster also
with a more "on-demand" response time.

Will do some more testing this evening after regular business hours...