Ersatz Definition Files
Updated October 2014
Ersatz devices are defined in one or more ersatz definition files, each of which is activated by a corresponding ERSATZ statement in miame.ini. By convention, these files are stored in the DSK0:[1,4] directory, with the first (and main) one being called ersatz.ini. If there are additional ersatz definition files, these are typically named xxxxx.ERZ where xxxxx is some kind of helpful allusion to the source or nature of the definitions contained in that file.
Each ersatz definition file line must match one of the following formats:
ersatz-device: =real-device:{[p,pn]}
++include real-device:file.erz{[p,pn]}
ersatz-device: =%INCDEV%:{[p,pn]}
Definitions
ersatz-device
the name of the ersatz device being defined: one to ten alphabetic or numeric characters, starting with an alphabetic character, and immediately followed by a colon.
real-device
the name of a "real" device, defined via a DEVICE statement in miame.ini. It must be immediately preceded by the equals (=) symbol, and immediately followed by the colon. The real device names must be three or four alphabetic characters, followed by one or two numeric digits, with a maximum length of five combined characters.
[p,pn]
an optional directory. If not included, then the ersatz device name can be used just like a real-device name in file specifications, meaning that you can optionally include a [p,pn] at that time.
file.erz
an arbitrary file name and extension of another ersatz definition file to "include" (i.e. effectively insert) into the current file. Note that contrary to the normal convention of ersatz definition files being in DSK0:[1,4], the ++INCLUDE feature is most useful with ersatz definition files that are stored on some other device. See %INCDEV% below for more details.
%INCDEV%
This literal pseudo-environment variable may be used in place of a real-device reference within an ersatz definition file that has been ++INCLUDE'd, and will be interpreted as the real-device that was in the ++INCLUDE statement. See ERSATZ ++INCLUDE Statements for more details.
Whenever A-Shell attempts to decode an DevPPN-style filespec, it compares the device part of the specification against the ersatz definitions first, before then comparing against the DEVICE definitions from miame.ini. So it is actually possible to "redirect" a real device by redefining it as an ersatz. For example, the ersatz definition DSK1:=DSK0: would effectively redirect all DSK1: references to DSK0:, even if DSK1: was a real device.
If the device is not found in either the list of ersatz definitions or real device definitions, then the last loaded ersatz file (i.e. the one referenced in the last ERSATZ statement in miame.ini) will be reloaded, assuming that a minute has passed since the last time it was reloaded. So you can effectively add ersatz definitions without re-launching A-Shell, although the value of this is limited since re-launching A-Shell only takes a few seconds.
Examples
Valid ersatz file entries look like this:
SYS:=DSK0:[1,4]
LIB: =DSK0:[7,0]
DSK100: =DSK99:
AA12345678:=ZZZ12:[345,678]
The ersatz definition file that is distributed with A-Shell and invoked by default, ersatz.ini, looks like this:
OPR:=DSK0:[1,2]
SYS:=DSK0:[1,4]
DVR:=DSK0:[1,6]
CMD:=DSK0:[2,2]
LIB:=DSK0:[7,0]
HLP:=DSK0:[7,1]
BOX:=DSK0:[7,2]
BAS:=DSK0:[7,6]
SBX:=DSK0:[7,6]
MAC:=DSK0:[7,7]
ASHCFG:=DSK0:[1,7]
PTR:=DSK0:[1,7]
ASHLPD:=DSK0:[1,25]
FAXWRK:=DSK0:[1,26]
ASHBAS:=DSK0:[907,6]
ASHINC:=DSK0:[907,16]
Another example:
++include SOS6:SOSLIB.ERZ[1,4]
Within an ersatz definition file that has been ++INCLUDEd, the following would be legal:
SOSFUNC:=%INCDEV%:[907,10]
History
2014 October, A-Shell 6.1.1393: Add ++INCLUDE capabilities
