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Path: utzoo!mnetor!seismo!gatech!hubcap!ncrcae!ncr-sd!hp-sdd!hplabs!ucbvax!XEROX.COM!"James_A._Gray.OsbuSouth"
From: "James_A._Gray.OsbuSouth"@XEROX.COM
Newsgroups: comp.os.vms
Subject: Re: How to get multi-level command history to work?
Message-ID: <870625-035641-3204@Xerox>
Date: Thu, 25-Jun-87 06:56:17 EDT
Article-I.D.: Xerox.870625-035641-3204
Posted: Thu Jun 25 06:56:17 1987
Date-Received: Sat, 27-Jun-87 04:26:56 EDT
Sender: daemon@ucbvax.BERKELEY.EDU
Distribution: world
Organization: The ARPA Internet
Lines: 60

Here's a new question, which I'm surprised hasn't been discussed
here already.  The version 4 terminal driver provides for recall
of the previous command line, and DCL somehow extends this to the
last 20 lines.  More recently, DEBUG and CMS (and probably
others) have also acquired the same functionality.

The obvious question is, how can I make my own interactive
applications interact with the terminal driver to provide deeper
command history?  I am sure that there are undocumented terminal
driver qio's which implement this, and I could go off and wade
through the fiche, but surely someone out there knows, and I'm
sure many people would be interested to hear how.

	The answer to this question is to use SMG$READ_COMPOSED_LINE.
	The following sample program (FORTRAN) shows what needs to
	be done to use this feature in a program which does not use the
	SMG routines for screen I/O.  Note that it defines a 30 line recall
	buffer.

		Jim

	PROGRAM SMG
C
	PARAMETER
	1	RECALL_SIZE	= 30
C
	CHARACTER
	1	RECEIVED_TEXT*132
C
	INTEGER
	1	KEYBOARD_ID,
	1	KEY_TABLE_ID,
	1	RECEIVED_STRING_LENGTH,
	1	SMG$CREATE_KEY_TABLE,
	1	SMG$CREATE_VIRTUAL_KEYBOARD,
	1	SMG$DELETE_VIRTUAL_KEYBOARD,
	1	SMG$READ_COMPOSED_LINE,
	1	STATUS
C
	EXTERNAL
	1	SMG$_EOF
C
10	FORMAT (' Echo input: ',A)
C
	STATUS = SMG$CREATE_VIRTUAL_KEYBOARD (KEYBOARD_ID, , , , RECALL_SIZE)
	IF (.NOT. STATUS) CALL LIB$SIGNAL (%VAL(STATUS))
	STATUS = SMG$CREATE_KEY_TABLE (KEY_TABLE_ID)
	IF (.NOT. STATUS) CALL LIB$SIGNAL (%VAL(STATUS))
1000	STATUS = SMG$READ_COMPOSED_LINE (KEYBOARD_ID, KEY_TABLE_ID,
	1	RECEIVED_TEXT, 'SMG Demo> ', RECEIVED_STRING_LENGTH)
	IF (STATUS .EQ. %LOC(SMG$_EOF)) GOTO 9000
	IF (.NOT. STATUS) CALL LIB$SIGNAL (%VAL(STATUS))
	WRITE (UNIT=*, FMT=10) RECEIVED_TEXT(1:RECEIVED_STRING_LENGTH)
	GOTO 1000
C
9000	STATUS = SMG$DELETE_VIRTUAL_KEYBOARD (KEYBOARD_ID)
	IF (.NOT. STATUS) CALL LIB$SIGNAL (%VAL(STATUS))
	CALL EXIT
C
	END