[Info-vax] /END=label

[Marc Van Dyck]

osuvman50 at gmail.com laid this down on his screen :
> On Monday, August 27, 2018 at 7:21:53 AM UTC-4, John Reagan wrote:
>> On Monday, August 27, 2018 at 2:56:56 AM UTC-4, Marc Van Dyck wrote:
>>> One last question - for now - maybe...
>>> 
>>> In the DCL READ command, there is a qualifier /END that branches the
>>> current procedure to a label if an end of file condition has been
>>> reached.
>>> 
>>> Is there a - possibly undocumented - way to implement something similar
>>> in a user-written program implemented as a DCL command ?
>>> 
>>> -- 
>>> Marc Van Dyck
>> 
>> The best you have it write a program that uses LIB$GET_SYMBOL, 
>> LIB$SET_SYMBOL, and/or return something via $STATUS and then have the DCL 
>> query the symbol and branch as desired.  A program cannot control DCL's 
>> command processing flow from inside the program.
> The program can exit via LIB$DO_COMMAND with the command being a GOTO 
> statement.

Setting return value in $STATUS is what I do right now. But there is
unfortunately no way in DCL to test a condition rather than hardcoding
the numerical value returned by $STATUS in the code. This I find rather
ugly.

But the suggestion of using lib$do_command seems indeed a possibility.
I will try that, although I'm not sure it will work. I would have
appreciated to receive an explanation about how $ READ does it...

-- 
Marc Van Dyck