[Info-vax] SET DEFAULT iterative logical name translation

[alanfe...@gmail.com]

On Monday, October 25, 2021 at 9:25:10 PM UTC-4, alanfe... at gmail.com wrote:
> On Monday, October 25, 2021 at 3:47:23 PM UTC-4, Dave Froble wrote: 
> > On 10/25/2021 2:28 PM, alanfe... at gmail.com wrote: 
> > 
> > > But it does a lot more than that. SET DEFAULT had 2 or 3 silly bugs that I figured wouldn't take long to fix. 
> > What bugs? I've never seen any.
> I posted on earlier in the thread. I think it's even mentioned in the docs once, but I don't recall where and doubt I can find it. 
> 
> Here is my summary of them:
> The DCL program SET DEFAULT has two problems with nested logical 
> names: 
> 
> 
> 1.) If the first translation has a trailing colon and there is no 
> explicit directory-spec in the second translation, SYS$DISK is changed 
> to the 1st translation and the directory portion is not changed. The 
> "actual" current directory remains hidden in SYS$DISK.
> [ I assume this mean if you specify <LNM>:[directory] ]
> 2.) If the 1st translation has no trailing colon, then only the 
> directory portion of the default is changed! This can leave SYS$DISK 
> incorrect thereby leaving the default incorrect.
> [This is the example posted by someone long ago which I put in one of my first posts in this thread.]
> Additionally, in certain circumstances, SET DEFAULT returns an error 
> but still changes your process to a bad default.
> [Unfortunately, I don't recall any examples of this.]
> > -- 
> > David Froble Tel: 724-529-0450 
> > Dave Froble Enterprises, Inc. E-Mail: da... at tsoft-inc.com 
> > DFE Ultralights, Inc. 
> > 170 Grimplin Road 
> > Vanderbilt, PA 15486
> AEF

The main problem happens when your equivalence name is a logical name and you don't include the colon. For example:

$ DEFINE HOME SYS$LOGIN

is potentially troublesome. The better way is 

$ DEFINE HOME SYS$LOGIN:

I found that if you always include the colon as above, you don't get into trouble.
Still, there was some rare case where you get a fatal error but it set your default anyway. Unfortunately, I don't recall what that was. If I stumble upon it later I will post it here.