Notes on the REDIRECT driver                August 1991 P.A. Borman


I read an article recently about the Macintosh. It's new operating system,
System Seven, has a facility called aliasing, which it's users are raving about.
Similar facilities are available on Unix systems (so I'm told..)

It allows you to assign names (or aliases) to devices or files. This is either
as mnemonics, or for transparent re-direction of IO. The original name is still
available as an alternative name, hence the term 'aliasing'.
It's such a simple idea I can't believe it hasn't been thought of before.

I've called it REDIR, although you never see the name as it's impossible to
open a channel directly to it.

A sample boot might be....

100 LRESPR flp1_REDIR_bin
110 REDIRECT printer TO par: rem easy name to remember
120 REDIRECT ser1hr TO nul: rem if Quill can't find it's printer dat it uses
        SER1HR which locks the machine unless you've a serial printer attached.
130 REDIRECT screen TO scr_500x200a6x50: rem another easy name to remember
140 REDIRECT mac TO win1_asm_gst_assembler_bin: rem and another
150 etc..

I can then EX MAC without having to remember where it is, and without setting
prog_use to point to it. It's easier to COPY file TO printer, or COPY file TO
screen, than having to remember (and type) a long scr_nnxnnannxnn string.

You can also use REDIRECT as a primitive file access protection system. If you
REDIRECT win1_asm_gst_a_bin TO "**secret file**", or any other silly (non-
existent) name, you will find you can't exec it, or open it, look at it etc,
although it still appears in the directory as normal.
If you've used line 140 above, you can still exec mac, but only you know the
alias you set for it, so it's semi-protected from unauthorised access.
You can also prevent someone reading a directory by REDIECT flp1_ TO '*NO*'

One final point, there are two new keywords linked in....

REDIR_LIST[#n]          list currently active aliases to #n, default #1

REDIRECT alias_name[,real_name]            as examples above

REDIRECT with one parameter removes that alias_name from the list, eg
REDIRECT screen removes the alias set by line 130 above. Easy really.