NetNews Usenet Archive 1992 #27/NN_1992_27.iso/spool/comp/os/vms/18199

Internet Message Format | 1992-11-18 | 2.5 KB

Path: sparky!uunet!sun-barr!cs.utexas.edu!swrinde!elroy.jpl.nasa.gov!nntp-server.caltech.edu!SOL1.GPS.CALTECH.EDU!CARL
From: [e-mail] (Carl J Lydick)
Newsgroups: comp.os.vms
Subject: Re: The problem with $CREMBX System_Service
Date: 19 Nov 1992 03:00:09 GMT
Organization: HST Wide Field/Planetary Camera
Lines: 32
Distribution: world
Message-ID: <[e-mail]>
References: <[e-mail]>,<[e-mail]>
Reply-To: [e-mail]
NNTP-Posting-Host: sol1.gps.caltech.edu

In article <[e-mail]>, [e-mail] (Paul S. Winalski) writes:
=
=The DCL command interpreter uses RMS to read its input file.  RMS is a record-
=oriented I/O system.  When the input device is a terminal, the sequence of
=characters up to a carriage return (or other similar line-terminating control
=character) is considered a single record.  When the input device is a mailbox,
=RMS considers each message in the mailbox to be a separate record.  You are
=reading characters one at a time from the terminal and then writing them one
=at a time using $QIO to the mailbox.  Each character thus ends up as a separate
=message, and is seen as a separate record by DCL.

The fault is not in RMS.  MAILBOXES ARE RECORD-ORIENTED DEVICES.  You can't
read a single character from a mailbox (well, you CAN, by using $QIO[W], but
the only character you can read singly is the first character of a record, and
then you lose the rest of the record).

=The solution is to buffer characters inside your program until you read a
=CR from the terminal, then write the buffered string (not including the CR) to
=the mailbox using one $QIO.

Or have the application that's reading the mailbox buffer what it reads until
it sees a CR in the data its reading from the mailbox.  Both techniques are
equally effective, and I'd choose the one for which obtaining and modifying the
source code is easier.
--------------------------------------------------------------------------------
Carl J Lydick | INTERnet: [e-mail] | NSI/HEPnet: SOL1::CARL

Disclaimer:  Hey, I understand VAXen and VMS.  That's what I get paid for.  My
understanding of astronomy is purely at the amateur level (or below).  So
unless what I'm saying is directly related to VAX/VMS, don't hold me or my
organization responsible for it.  If it IS related to VAX/VMS, you can try to
hold me responsible for it, but my organization had nothing to do with it.