PWD V 2.0

From: Al Hawley, Znode 2 (Ladera Znode), (213)-670-9465
Date: 10/25/89

Credits and thanks to Jay Sage, Cameron W. Cotrill, and
Howard Goldstein for help in design and debugging. I always
feel secure after Howard has picked the flaws out of a program!

A few weeks ago, one of my Znode callers complained about PWD.
It seems that he has a LARGE number of directories on his HD,
and the PWD display simply vanished off the top of the screen
before it stopped! It touched a nerve. I intentionally keep the
NDR small, and load a new one when my attention needs to turn to
system areas not 'named' in the current NDR. Awkward, but it works.
So I put paging into PWD for him. And then I began to consider, with
considerale prompting from Jay Sage and Cam Cotrill, OTHER ways of 
managing the PWD display. During the last year, Cam and I have been 
swapping ideas for a Finite State Machine. An FSM is ideally suited 
for implementing a command tail parser; in fact, that's how really 
complex parsers for such things as compilers work. 

"When you get a new hammer, all the World looks like a nail!"

Since the OTHER ways of managing PWD displays involved a new syntax
that would be tedious to write (and change when users don't like it!),
the new PWD looked like an ideal "nail" for the FSM "hammer"!

The results are in this package. The source for PWD is no longer just
one file, although it COULD be melted together. Instead, the FSM is
a separately assembled file, FSMACH.Z80. Similarly, the State Tables 
and their support routines are another file, PWDCMD,Z80. They are
combined during linking with the main PWD.Z80 assembly. A third
component, BITS.Z80, contains some handy bit-twiddling routines
imported from ARRAYS.LBR for manipulating bits in drive vectors.

The syntax for PWD2 is described below. It is very forgiving; by
design, PWD2 does two things: displays the directories, or displays
HELP. No error messages. To display directories and password, the
original syntax was:

		PWD P

This has been changed in the new version to

		PWD /P

which, in addition to being consistent with other Z utilities,
removes a parsing problem. (The letter P is also a drive letter!)

PWD2 takes an indefinite number of arguments, in any order. Easy,
with the FSM. This means that a command line like

		PWD <arg> // /P

will result in nothing but a help screen display. The parser detects
the '//' and acts on it. Here's the syntax. Many other changes 
(not mentioned here) are to be found in PWD.HST.

If you have a terminal that supports 132 column mode, set it up that
way (don't forget to tell Z3ENV about the change!) and then give
PWD a try. PWD ajdusts the display for current screen size.

Syntax:		PWD  [<arg>...]

There are 3 argument types, identified as follows:

	<D>: terminator indicates drive selection list

	/<o> The only options is P'. Anything else is
		a HELP invocation.

	<mask> a set of characters from which a legal file
		name could be made. No delimiters. This is
		automatically wild-carded as if '*' had been
		appended. If the argument has more than 8
		characters, only the first 8 are used. The
		rest are ignored.

  whitespace is spc, tab, comma, and CR (after last argument)

  <mask> and /o are terminated by whitespace

  <D>: may be followed by whitespace, but it's not required

  <D> may be a list of one or more of the letters A...P
    the list may include a range like B-F

	examples of valid drive lists:

	a:  bcd:  B-FM:  A-CJ-M:  HBJMF:

  a tilde causes subsequent members of the list to be excluded

	for example:

	~bc:       (no display for drives B and C)
	~AH-P	   (no display for drives A and H through P)

  arguments may be in any order, and may be repeated if separated
  by whitespace. 

	A-P: ~lmno:  displays all drives except L,M,N, and O.

  Whitespace is not required after a colon;

	A-P:~LMNO:  is the same as the previous example.

OTHER THINGS IN THIS LIBRARY

PWD is configurable with ZCNFG.COM and the configuration overlay
PWD.CFG. The overlay is included here; ZCNFG is readily available
from Znodes. The source files for PWD.CFG are included in PWDCFG.LBR
which is also included here. These files provide a simple example
for making .CFG files, should you like to build one for some other
program, or even expand on PWD's configuration options.