To:     ZCPR3 users with BackGrounder ii
From:   Bridger Mitchell and Jay Sage
Subject: BGii customization scripts
Date:   4/17/87
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Jay has contributed some excellent Z-system alias scripts for automating
the BGii startup and shutdown operations.  In addition, he shows how
to change the names of BGii built-in commands.  Useful in their own
right, these scripts are also a model of a well-designed system
environment.

You will need to modify the scripts to reflect your own system's
directory names and custom files.  The FIXBG addresses will vary,
depending on BGii version and the disk parameters of your swap drive.
And BGHIST and BGERRH require BGHIST.OCP.

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    Here are the ARUNZ (renamed to CMDRUN.COM) scripts I use for
the various BG-related operations.

1. script BG

  This script is used to engage BGii.  It goes to the required directory,
  clears the shell stack if necessary because BGii will invoke BGHIST, and
  then returns to the directory from which this alias was invoked.  The
  explicit directory references before some of the commands just speeds
  things up a little.

       SYS:                            ; Go to directory with LOADBG
       IF SH                           ; If a shell is currently running
       SYS:SHCTRL C                    ; Clear shell stack
       FI
       SYS:LOADBG                      ; Invoke BG (runs alias STARTBG)
       $D0$U0:                         ; Return to original directory


2. script STARTBG

  This script is the BGii startup alias.

       TIME ON                         ; Turn on time display in prompt
       KEYS GLOBAL                     ; Load my global key definitions
       OCP BGHIST                      ; Load OCP with BGHIST and BGERRH
        FIXBG (leading space)          ; Script to patch BG swap file
       BGHIST                          ; Load BG history shell
       BGERRH                          ; Engage BG error handler
       CLS                             ; Clear the screen


3. script FIXBG

  This script makes the changes to the BG swap file to rename some of the
  resident commands.  It could be a part of the main STARTBG script, but I
  prefer to keep this separate.  I change the ECHO command to ECKO so that
  my transient ECHO.COM, which runs at 8000H, will be used instead.  I also
  shorten PEEK to P and RESET to R.

       SYS:DU GF,+9,CA53 K,W,+,CA5A    ,CA7A     ,W,X

  Here are the operations performed by each of the disk utility commands:

       GF                      ; Go to disk group 000F (the group
                               ; ..containing the command dispatch table)
       +9                      ; Advance 9 records to the one containing
                               ; ..the entry for the ECHO command
       CA53 K                  ; Change-Ascii at byte 53H of the record,
                               ; ..putting in a 'K' in place of the 'H'
       W                       ; Write the changed record out to the disk
       +                       ; Advance to the next record on the disk
       CA5A....                ; Another Change-Ascii (note four spaces,
                               ; ..one to separate command from argument
                               ; ..and three to replace 'EEK' in 'PEEK'
       CA7A.....               ; Another change in same record (five spaces
                               ; ..in all, four to replace 'ESET' in
                               ; ..'RESET')
       W                       ; Write the changed record out to the disk
       X                       ; Exit from DU3 disk utility

  The actual records containg the command dispatch table varies with each
BGii release.  What has confused me a bit lately is the appearance in the
swap file of two command lists that each look like a dispatch table.  Only
one is, and the real table has to be determined by trial and error.


4. script BGOFF=OFF (two alternative names for same alias)

  This script exits from BGii and reestablishes the ZCPR system.  Since
  my configuration of BGii uses the RCP space, I have to restore the
  environment descriptor and the RCP code.

       IF BG                   ; If BG is currently running
       BG OFF                  ; BGii command to exit
       SYS:SHCTRL C            ; Clear shell stack (of BGHIST)
       SYS:LDR SYS.ENV,SYS.RCP ; Restore environment and RCP
       SYS:ERRSET SYS:VERROR   ; Set up ZCPR error handler
       ELSE                    ; Else if BG not running
       ECHO BG NOT RUNNING     ; Tell user
       FI


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