GF - A Generalized Filter

                              Dave Ramsey

   GF is hereby placed in the public domain, February 1, 1989.

   The intent of GF is quite simple - to allow the user to replace any 
character in a specified input file with any other character on a global 
basis. The reason that I wrote GF was because I frequently get text 
files that were probably prepared on Un*x systems and which have only 
bare linefeeds as line terminators. To read these files, I needed a 
quick tool to change all LFs to CRs; GF fills that bill.

   In order to use GF, the user must specify four arguments. These are 
the input file, the output file, the search character and the 
replacement character. GF allows the user to specify control characters 
for either the search character or the replacement character by 
preceding them with a '^'. Likewise, since ZCPR and CPM convert the 
command line to all uppercase, GF allows the user to specify a lowercase 
character by preceding that argument with a `~` character. For instance:

  A0>GF INFILE.TXT OUTFILE.TXT ^J ^M

will convert all the linefeeds in INFILE.TXT to carriage returns in the 
file OUTFILE.TXT. (I've used it often in this mode to clean up documents 
prepared on Un*x systems since Un*x uses only a bare linefeed as a line 
terminator.)

   Likewise, the command:

  A0>GF INFILE.TXT OUTFILE.TXT Z ~z

will convert all uppercase Z's to lower case z's.

   If invoked with no arguments or the wrong number of arguments, GF 
will present a help screen to the user. This help screen is presented 
below:

GF, Version 1.0 - A Generalized Filter.
Syntax:
        GF du:fn1 du:fn2 oldch newch
   Where:
       du:fn1     is the input file spec;
       du:fn2     is the output file spec;
       oldchar    is the search character; and
       newchar    is the replacement character.,
   A ^ character before either oldchar or newchar
   tells GF to convert it to a control character.
   A ~ character before either oldchar or newchar
   tells GF to convert it to lowercase.
   i.e. ^M is a carriage return and ~M is an "m"





NOTES: (1) While I've written a number of Turbo Pascal and Turbo 
Modula-2 programs for my Z80 Ampro system, Ive not had the time to 
involve myself deeply in Z80 assembly language programs. Job, personal 
affairs, and many hours of overtime using Fortran on IBM and Unisys 
mainframes generally dampened my enthusiasm for developing Z80 and 
Z-System software. This is my first stand-alone Z80 application and 
except for the changes I made to my Sanyo MBC-1000 BIOS three years ago, 
is probably the largest Z80 project I've undertaken to date. So if my 
coding style isnt the best, or if I've made some obviously foolish 
errors, please be gentle with the criticisms! I want to hear about them 
but don't need a reprimand.
   (2) I'm interested in using the Z-System SYSLIB routines as much as 
possible. If I could have used them better or if there are routines to 
do things that I have done, let me know.
   (3) If there are additional things you would like in GF (I can't 
imagine what else anyone would want in a simple, generalized file 
filter) leave me a message on Z-Node #3 (Newton Center), Z-Node #2 
(Ladera), or Z-Node #24 (Cedar Mill) *OR* go ahead and add it yourself. 
After all, GF is in the public domain!