Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!mnetor!uunet!seismo!rutgers!ucla-cs!zen!ucbvax!EQL.Caltech.EDU!rankin
From: rankin@EQL.Caltech.EDU (Pat Rankin)
Newsgroups: comp.os.vms
Subject: re: Command input from a file continued, and maybe a bug in VMS
Message-ID: <870807140223.01g@EQL.Caltech.Edu>
Date: Fri, 7-Aug-87 17:03:42 EDT
Article-I.D.: EQL.870807140223.01g
Posted: Fri Aug  7 17:03:42 1987
Date-Received: Sun, 9-Aug-87 13:24:52 EDT
Sender: daemon@ucbvax.BERKELEY.EDU
Distribution: world
Organization: The ARPA Internet
Lines: 27

< attempting to redefine SYS$INPUT inside a program which uses LIB$GET_INPUT >

> All variations of the program (like read many lines instead of one, check
> for EOFs and such, which i ommited here for the sake of brevity) seem
> completely consistent: what counts for LIB$INPUT is not the translation of
> SYS$INPUT at the time you call it, but AT THE TIME THE PROGRAM WAS INVOKED.
> If SYS$INPUT points to the terminal at the beginning of the program, all
> the LIB$SET_LOGICALS can't change the mind of LIB$GET_INPUT.
>
> The only question it: why is this so ? What use is LIB$SET_LOGICAL in this
> case ? Is this a bug ? Should i SPR it ? Am i stupid ? Is there something
> tricky (maybe using the right logical name table) i overlooked ?

     The logical name is used by RMS the first time (and only the first
time) that the routine is called (not at image activation time).
     I haven't looked into LIB$GET_INPUT, but I have disassembled
LIB$PUT_OUTPUT and I can tell you that it works in the following manner:
  -- the first time it is called, it uses $CREATE and $CONNECT to open a
file called "SYS$OUTPUT" (a logical name referencing something).  It
saves the RMS ISI (Internal Stream Identifier, which is essentially a
pointer to the open file).  It then uses $PUT to write to the file.
  -- on subsequent calls, it retreives the ISI, builds a temporary RAB
structure, and issues a $PUT.
     Undoubtedly LIB$GET_INPUT functions similarly.  This should explain
your problem, but it also illustrates that LIB$GET_INPUT cannot do the
job you want to make it do.
                                         Pat Rankin