[Info-vax] Still no DIR/SORT_BY_TIME

[Johnny Billquist]

On 2015-08-19 01:17, David Froble wrote:
> Johnny Billquist wrote:
>> On 2015-08-18 20:01, David Froble wrote:
>>> Simon Clubley wrote:
>>>> With RSTS/E, when opening a file, you could specify various options
>>>> using a mode field which was a bitfield encoded integer. Opening a file
>>>> with mode 4096 allowed you to open and read a file when you normally be
>>>> blocked due to an incompatible open mode from another currently running
>>>> program.
>>>
>>> Locking is ALWAYS a cooperative thing.  It's always possible to not
>>> conform to locking.  Just be careful when doing so.  Read only usually
>>> is safe.
>>
>> Not so. Write locking is (in RSX) enforced by F11ACP, and is not left
>> as an exercise to the programmer.
>> However, read locking is something RMS does without F11ACP enforing.
>> Same thing with block locking.
>>
>>>> It's been a _long_ time since I last used it, but I think (IIRC) it
>>>> could even be used to see the current contents of a file which was
>>>> exclusively opened for writing by another program. (Assuming you had
>>>> suitable access rights to the file of course.)
>>>
>>> Well, since as far as I know, RSTS/E was definitely cache nothing, yes,
>>> if it's on the disk, you should be able to read it.
>>
>> In RSX, it's not that simple. Various meta-data is not written out
>> until explicitly requested from a program, so as well as local buffers
>> in the program, various information, such as EOF position, is not
>> visible to other programs just because one program have "written" it.
>>
>>     Johnny
>>
>
> Ah, I do believe I was referring to RSTS/E only.  And, I haven't used it
> since 1978, so I could mis-remember some things.

Ok. My misunderstanding then. I thought you meant it in a more general 
way. I've used RSTS/E a lot in the past, but forgotten way more than I 
remember, so I'll take your word here.

> You also mention RMS.  I don't think that's the only option on either
> RSTS/E or RSX.  Note, never used RSX.

True. RMS is not the only options in RSX. However, the write lock on 
files, like I said, is done by F11ACP, which both RMS and FCS use. So 
that locking is in place no matter what library you use.
I mentioned RMS specifically for read locking out, which, if it actually 
works (I haven't checked) must be done within RMS, as F11ACP do not give 
you that.

> I also have some considerable experience with locking ....

No point in me arguing that one. :-)

	Johnny