[Info-vax] Backup API mailbox oddity

[osuvman50 at gmail.com]

On Thursday, January 11, 2018 at 11:57:34 AM UTC-5, Stephen Hoffman wrote:
> Based on what I see here, I'd just spawn BACKUP directly and capture 
> errors via the termination mailbox.
> 
> I don't know that the BACKUP API was ever tested with this 
> mailbox-as-input approach, and it certainly appears that it's not 
> working or not working very well.

If I use system() to spawn the command, it still requires a preceding EOF. If
I use LIB$SPAWN(), it requires 2 EOFs before sending the filenames.  If I use
LIB$SPAWN but make the mailbox the spawn's SYS$INPUT and specify
sys$input/inputfiles on the backup command, it also requires 2 spurious EOFs.

> 
> If you want to maintain the use of that that mailbox as a way to pass 
> in the list of files, then I'd try specifying that mailbox on the 
> BACKUP DCL command line as the first parameter.  Use a leading @.   I 
> suspect a spawn will involve less source code, too.

I don't think I'll bother.

Building the control structure with large list of input files isn't really that difficult in C, but it would be easier if the API had a no-op flag structure to use as padding or a chain-to address option.