[ KAY*FOG RBBS | MEXREAD.ART | published 06/16/85 ]

MEX READ: AUTOMATED TRANSFER OF FILES WITH MEX: THE "READ" COMMAND
          by Rick Charnes

MEX is the most exciting public domain modem program available
for CP/M computers.  What follows is a fairly detailed discussion
of a use of MEX's most unique and dynamic capability, its READ
command.  Beginners might find it difficult to follow.  It
assumes a prior working knowledge of MEX, and some familiarity
with its very long documentation.  Novices might want to read my
introductory article to MEX, also available with the A) command
here on KAY*FOG.

Here are the files that I've developed in order to automate the
transfer of files with MEX.  I want to emphasize that this is not
true "batch" transfer; it has nothing in common with the

Christensen "B" (batch) command as it does not have wildcard "*"
capability.  You can not get it, for instance, to send all files
with the extension ".LBR" with a "*.LBR" command.  Each file must
be listed by name.  I prefer calling it "automated" transfer
rather than "batch," though it is batch in the sense that it can
send or receive a group of files with a single command.  The
difference is that these files must all be named individually.

The advantage of this way of file transfer is speed and accuracy.
No longer do you have to make sure you spell the name of the file
correctly TWICE - once while invoking the RCP/M's XMODEM function
and then again when receiving with your own "R" command.  And you
are spared many extra keystrokes and time.  And of course,
there's the most important aspect: it's FUN!  There's nothing
like the thrill of watching the computer do what you've
programmed it do.  As Irv Block says, "All of this unattended,
while you file your nails or go for coffee."  Ah, the true
purpose of computers is revealed...

The way that this is done is through one of MEX's most
fascinating and exciting capabilities, its READ command. One
prepares a file beforehand, using a text editor or wordprocessor,

a file which MEX will "read" when online.  It is very similar to
CP/M's SUBMIT utility.  Simply be sure to name the file with the
extension ".MEX".

I have named the following file "TAKEMANY.MEX", though you can
call it anything.  (In the voluminous MEX literature, similar
files are often called "GET.MEX").  Then when you are online and
ready to down- or up-load, you simply type "READ TAKEMANY" (or
"SENDMANY") on MEX's command line.

Or, even better, turn on MEX's "read command extender" by typing
STAT EXTEND ON.  With EXTEND on, MEX interprets any command
entered on its command line differently from how it normally
does.  It first searches to see if it is a normal command from
its command "table. " If not, it "passes it on" to READ and
assumes it's a READ command.  This way, you don't have to type
the word "READ" since it is assumed.  In other words, if you type
simply "TAKEMANY" after the MEX prompt, it will automatically
search for the file "TAKEMANY.MEX" on disk and "submit" the
commands from it.

Here's the file:


STAT TRIGGER ">"
PREFIX "XMODEM S "
SENDOUT "{1}"
R {1}
SENDOUT "{2}"
R {2}
SENDOUT "{3}"
R {3}
SENDOUT "{4}"
R {4}
SENDOUT "{5}"
R {5}

The numbers within the brackets are considered parameters, and I
suggest you read the printed doc file for the explanation of
these little guys, though it's similar, again, to SUBMIT's
parameters.

This is to receive several files in an automated sequence from an
RCP/M.  Then when you've logged onto a network ("BBS") and you're
in the RCP/M, simply type:


TAKEMANY FN1.FT FN2.FT FN3.FT FN4.FT

etc., where FN1.FT, FN2.FT, etc. are the names of the files you
want.  If you have fewer than 5, that's OK.  MEX will just give
you an error message: "parameter error: line #n" and the read
command will simply halt.

What this file does is first it sets the PREFIX of any SENDOUT
string you're going to send as 'XMODEM S '.  It'll also wait
until it sees a ">" from the RCP/M before sending its string.
Of course ">" is the CP/M prompt you will get from the RCP/M.
This TRIGGER command is excellent and very important for file
transfer.  Nothing will be SENTOUT until MEX sees this all-
important ">".  When it does, BAM!!  There she goes.  Then - if
transmission is incorrect, and if WTECHO is on (it should be!) it
waits till it sees another ">" then sends it out again until it's
received correctly!  Watching this process on your screen,
especially when it sends a "cancel" character if the transmission
is incorrect and it needs to be sent again, is quite beautiful to
behold!


So with the prefix set, it then sendsout the string that you
enter on its command line, which in this case is the filename.
It then enters this string into the parameters {1}, {2}, etc. in
the READ file.

In other words, you're sending out to the RCP/M the prefix
"XMODEM S " and then the name of the file you want, so altogether
you're sending out "XMODEM S FILENAME.TYPE".  Whatever you've
type on the command line after the word 'TAKEMANY' become the
parameters that it inserts into the READ file to be sent out as
SENDOUT.  Be sure to read the explanation of this in Ron Fowler's
long .DOC file.  Again, it's very similar to the SUBMIT command
with its parameters.

Then after MEX has inserted the parameters that you've typed on
its command line into the SENDOUT string, then it ALSO inserts
them into the line in the READ file where it says "R {1}" or "R
{2}", etc.  So after MEX has invoked the RCP/M's XMODEM capacity
and gotten it ready to send, it then dutifully goes back into
your computer and does the "R" command to receive.  And of course
again it sees those brackets, knows it's a parameter, and again
uses the parameter that you've entered on the read command line.

You're sending and receiving the same filename.

So what you're doing is having MEX tell the RCP/M to send what
you've entered into parameter 1, then it tells your computer to
receive what you've entered in parameter 1, and it continues on
its merry way until its exhausted all the parameters or until
number 5.

This concept of parameters can be very complicated.  It takes
some concentration at first, but it eventually all clicks
together quite nicely.

Remember that a READ command can operate on two levels: it can
SENDOUT strings to the BBS _and_ it can give commands internally
to MEX.  When it's SENDING OUT the string within the quotes is
sent to the remote, but other commands, such as the "R {1}" or a
STAT command or "PREFIX" in the above file (there are of course
many others!), are sent internally to your computer to set the
values of MEX.  It's important to get this sense of switching
back and forth between modes.  Anything that should be sent out
to the BBS should be sent as a SENDOUT string; anything you want
to tell MEX itself, internally, gets entered directly.


A slightly different way to write this file would be without the
use of the PREFIX command.  It would then appear as:

STAT TRIGGER ">"          <--- this is sent internally (to MEX)
SENDOUT "XMODEM S {1}"    <--- this string is sent to the BBS
R {1}                     <--- sent internally
SENDOUT "XMODEM S {2}"    <--- to the BBS
R {2}                     <--- (etc.)
SENDOUT "XMODEM S {3}"
R {3}
SENDOUT "XMODEM S {4}"
R {4}
SENDOUT "XMODEM S {5}"
R {5}

I just prefer to use the PREFIX command as it saves typing and
again -- it's more fun.


Now a word about WTECHO.   Be sure to turn STAT WTECHO ON.  THIS
IS VERY IMPORTANT for error detection feedback.  This turns
SODELAY off, which is not as good for our purposes.  What WTECHO
does is to verify (something like CRC checking, I guess!) that
the transmission of the SENDOUT and keystring characters are sent
properly.  You'll notice a real delay in the SENDOUT command and
your keystrings when you have WTECHO ON rather than OFF.  I like
it much better.  Only thing is, its efficiency is greatly
diminished when you're not in an RCP/M, such as sending logon
strings, as it generally looks for that TRIGGER character as a
cue to send out its string.  For this purpose, its use is greatly
problematic, as it's very difficult to find a single trigger

character (or one at all, for that matter!) for a complete logon
string.  I have found SODELAY, which is dependent on the WCHAR
and WLINE settings (normally used for time delays when sending a
file in terminal-mode) to be much better for sending out logon
strings.  Any feedback on this, though, would be appreciated.

But for file transfer with an RCP/M be sure to turn the trigger
character to ">" with STAT TRIGGER ">" so it knows what to look
for to SENDOUT and also for WTECHO to retry.  Since when sending
logon strings and also for Smartmodem commands (such as to turn
the modem speaker off and on, which can be done through a READ
file) there will be no trigger character to look for, I recommend
that the STAT TRIGGER ">" command be incorporated into READ files
for file transfers rather than CLONEd directly into MEX.

An alternate way to set up READ files is if you know the names of
the files you want before you log on.  In this case, what you do
is to have the READ file that you prepare off-line include the
names of the files.  This way, you save time and possible
mistakes typing them in on MEX's command line when you're on-
line, since you're not using parameters.


For instance, suppose you want to download the four files named
THIS.FIL, THAT.FIL, THIS.DOC, and THAT.DOC.  Your file should
look like:

STAT TRIGGER ">"
PREFIX "XMODEM S "
SENDOUT "THIS.FIL"
R THIS.FILE
SENDOUT "THAT.FIL"
R THAT.FILE
SENDOUT "THIS.DOC"
R THIS.DOC
SENDOUT "THAT.DOC"
R THAT.DOC

So you'll end up, assuming the prefix of "XMODEM S ", sending out
"XMODEM S THIS.FILE" which will invoke the RCP/M to send, and
then return to your computer and receive THIS.FIL, etc.

Just understand that when READ is reading the lines with SENDOUT
commands, it's sending them to the RCP/M, and when it's in the
lines with the "R" or "STAT" or "PREFIX" commands, it's talking

to your computer, that is, to MEX.

And of course both these files can be made to _upload_ files to
an RCP/M by simply making the PREFIX to be XMODEM R and the "R"
in the next line an "S".

Or this idea can be used to upload or download single files.  To
download a single file, make a READ file (always with the
extension of .MEX, remember), that looks like:

STAT TRIGGER ">"
SENDOUT "XMODEM S {1}"
R {1}

And to upload a single file, again, reverse the "R" and "S".
That's all.

An interesting idea I owe to one of the other articles I read is
using MEX's READ command to download a file but change its name
before it's placed on your computer's disk.  This would be
convenient for downloading files with the extension ".OBJ" which
you would want to change to ".COM."  You don't have to wait till

you're back in CP/M; you can have MEX do it for you.  Say you've
got a file called "TAKEC.MEX" (the C means "change" the name):

STAT TRIGGER ">"
SENDOUT "XMODEM S {1} {2}"
R {2} {1}

Then when you're in the RCP/M, you see a file you want, called
NSWP205.OBJ.  On MEX's command line, type:

          TAKEC NSWP205.OBJ NSWP205.COM

This reversal of parameters on the last line is what does it.
It will send out that full string, with both names.  But
apparently when XMODEM sees two strings, separated by a space, it
simply ignores the second and assumes it's dealing only with the
first.  So it does transmit NSWP205.OBJ.  But MEX "remembers" the
filename you've typed in for the second parameter.  Then, when
READ comes to the last line, this time it is READ that simply
ignores what is second on its line, here parameter number 1
(NSWP205.OBJ), and therefore receives only what comes first on
its line, parameter number 2, NSWP205.COM.  You can check on your

disk to make sure.  Neat, huh?

One caveat about READ files in general.  It's hard to understand,
but all the while MEX is reading a READ file, it is NOT in
terminal mode.  It _looks_ like it's in terminal mode; the
SENDOUT strings are sent directly to the computer network in what
looks like terminal mode, but you're NOT in terminal mode.  The
reason I emphasize this is that if you ever have a "T" (for
Terminal) command within a read file EXCEPT AS THE VERY LAST
COMMAND the READ file will simply stop.  So if you've set "T" as
your GLOBAL command, you must turn it off with the command
"GLOBAL".  (The word "GLOBAL" by it
put a "T" command in the middle of a file, simply escape manually
back to MEX's command mode and the READ file will continue.  "T"
can very properly be put as the _last_ command in a read file; it
will, in this case, put you successfully into terminal mode since
there are no more commands after it.  This is actually a good
idea since you will have to return to terminal mode manually if
you have more business on the RCP/M.

I hope I've explained A LITTLE about MEX's wonderful READ command
and some of the things it can do.  Experiment yourself - I'm sure
there are a lot more undiscovered roads to travel with this
incredible modem program.  As one of its many aficionadoes, Irv
Block, comments, "there may be as many different ways of
programming it as there are users." Let me know what experiences
you have.

Have FUN! - that's what MEX is all about!  Any questions - send
'em to me on the MEX CONFERENCE!

                                        Rick Charnes

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