[Info-vax] CRTL and RMS vs SSIO

[Greg Tinkler]

On Thursday, 7 October 2021 at 11:26:38 pm UTC+11, Simon Clubley wrote:

> How do you find byte 12,335,456 in a variable length RMS sequential file 
> without reading from the start of the file ? 
> 
> That's why there are restrictions on RMS supported file formats in an 
> application in some cases.

The same way it is done on Unix, calculate the block offset, go get it, and extract the byte.  no difference and nothing to do with the underlying format.

> > I always wondered why the CRTL did not have some smarts to present a VFC 
> > records as STMLF and vise-versa, effectively hiding the internal record
> > structures. This could be done via open using the VMS extension ?rfm=STMLF? 
> > which should be the default unless it is a binary file ?rfm=unf?. If the file
> > is VFC then CRTL could to the translation. Wishful thinking. 
> >
> This could not be the default. What if LF characters are part of the 
> existing data record itself ? You have just destroyed the meaning of 
> the file in that case.

Please read what I wrote, if the file has been opened "b" then don't, otherwise we need to assume it is stmLF.  Yup probably another logical to set the default but I'm pretty  sure if you create a new file using CRTL with the defaults then it will be stmLF anyway.

gt