[Info-vax] links and deleting directory trees (Re: Some questions on software for VMS 7.3 VAX)

[Johnny Billquist]

On 2016-01-22 20:11, Craig A. Berry wrote:
> On 1/22/16 9:28 AM, Stephen Hoffman wrote:
>> On 2016-01-22 15:00:53 +0000, Bob Koehler said:
>>
>>>    For at least ODS-2 and -5, the second name entered by ... "set
>>> file/enter", is an alias, not a hardlink.
>>
>> With OpenVMS V7.3 and later on OpenVMS Alpha and on OpenVMS I64, SET
>> FILE /ENTER creates either an alias or a hard link, depending on the
>> setting of the target ODS-5 volume.
>>
>> ODS-2 gets only aliases.
>>
>> The DCL command for both aliases and hard links is the same.
>>
>> What happens depends on the setting of the target ODS-5 volume.
>>
>> This is another example of a command or a routine that can do different
>> things based on some compatibility setting(s) located elsewhere.
>
> Yes, and even more to the point considering how the discussion got here
> is whether PCSI REMOVE, DELETE/TREE, and/or DFU DELETE/TREE have
> explicit designs around whether to follow links and what kind of links,
> or whether what you get is just the random intersection of the evolving
> behaviors of the lower layers.
>
> I would expect a tool designed to delete a directory tree to remove
> links but not follow them, at least by default, and in the case of PCSI
> I would expect it to only remove whatever it installed, whether that's
> both the link and the target or only the link.

The point with hard links is that you cannot tell if you are following a 
link or not, since all directory entries are hard links, at the bottom 
line. All hard links are equal.

An interesting distinction between aliases and hardlinks here, by the 
way. I have never seen that one before. Curious question then, how does 
VMS deal with if you create a hard link, but remove it as an alias? Or 
vice versa? Can you even tell if an entry is a hard link or an alias? 
What happens if you create both hard links and aliases to a file?

The only place where the distinction is made is in the handling of the 
reference count. You can you tell, when you remove something if it is an 
alias or a hard link?

	Johnny