SCO "lp -L" and filePro (was Re: PFPRINTER)

[Brian K. White]

----- Original Message ----- 
From: "Kenneth Brody" <kenbrody at bestweb.net>
To: <filepro-list at lists.celestial.com>
Sent: Friday, June 24, 2005 8:34 AM
Subject: SCO "lp -L" and filePro (was Re: PFPRINTER)


> Quoting Brian K. White (Fri, 24 Jun 2005 03:17:08 -0400):
> [... SCO's "lp -L" command to do local printing ...]
>
> How does lp send output to the local printer without colliding
> with the output of other programs which may be running at the
> same time.  For example, filePro is displaying its "generating
> output" messages on the screen while sending the output to lp.
> What prevents collision, and having filePro's display messages
> ending up on the printer?

Well it IS possible that it utilizes some special kernel interface designed 
just for that purpose that suspends the norml tty traffic just like 
digiboard & equinox drivers do.
They (digi/equinox serial card drivers) have this thing where they provide a 
seperate tty device for a virtual printer, and any random process may write 
to the print-tty at any time, and the driver manages looking up the correct 
printer-on-off codes from it's own config file and suspending the normal tty 
traffic in little bursts so that print and screen data do not mix and both 
ttys appear to work at the same time.

But I doubt it does that. I don't think it promises any magic like that. 
It's up to you to use the feature with the understanding of it's 
limitations.

So this should NOT be used in pmaint.

It CAN be used in a system command just fine. We have a centralized printing 
call table that includes a local print option, actually three local print 
options because FactWin provides 3 sets of printer on/off codes and you can 
define 3 different printers in the client). We use the binary "passthru" I 
mentioned earlier for the main printer "printer A" in facetwin, and a couple 
of little shell scripts for the printer B and C, in a system command, and it 
works terrifically. filepro does not write to the screen during a system 
command.

The only downside is you can't print graphics. The binary junk just doesn't 
survive the passthru mechanism.

There is an answer for that. There is a 3rd passthru code besides the common 
2, printer-on & printer-off. There is a 3rd code that says "printer on for 
the next n bytes".
And I'm not sure but I think n can only be up to 255 bytes or some other 
small number.
My guess is that the existence of such a code is to provide a way to print 
data that would have the printer-off code in it which would otherwise screw 
up the print job.

But I don't think many terminal emulators know that code and even if they 
did I don't know how I'd go about using it. I think it would require a 
special version of the passthru binary that examined the data and sent 
certain special chunks of the data using the alternate method. Filepro nor 
bbx nor probably any other similar application system certainly doesn't 
allow for such a mechanism. Using a special program in a system command 
should work fine though.

Brian K. White  --  brian at aljex.com  --  http://www.aljex.com/bkw/
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