Simtel MSDOS 1992 June/SIMTEL_0692.cdr/msdos/info/dostips6.arc/DOSBATCH

Text File | 1987-03-04 | 18.8 KB | 488 lines

                             Get SET
       (PC Magazine Vol 6 No 1 Jan 13, 1987 User-to-User)

     You can access the SET environment strings in batch files simply
by putting the set name inside a pair of percent signs (%).  This lets
batch files use the environment as a global memory area.  For example,
with a subdirectory on drive A: called |DOS, type:

SET DOIT=A:\DOS

Then create a batch file called D.BAT:

DIR %DOIT%

Typing D at the DOS prompt will display the directory listing for
A:\DOS.
     Editor's Note:  SET has been around for a long time as an
undocumented command, and from the pathetic description in the DOS
3.x manual, it might just as well be undocumented.  This technique
does work but just scratches the surface.  You can see the current
state of your environment, including all the variables you've set,
by typing SET.

-----------------------------------------------------------------
                       Easy Global Erasing
       (PC Magazine Vol 6 No 2 Jan 27, 1987 User-to-User)

     If you frequently delete all the files in the current directory
with the command DEL *.* and are tired of answering the question, "Are
you sure (Y/N)?", try the file DALL.BAT:

ECHO OFF
REN *.* $*.* >NUL
DEL $*.* >NUL
IF EXIST *.* DEL *.* >NUL

     This fools DOS into thinking it's deleting just a subset of all
the files in the directory.  It renames all the files to have a "$" as
the first character, then deletes those files.  The >NUL sends the "n
files deleted" message into the Twilight Zone.
     In the rare cases that two filenames differ only in the first
letter, or if the first letter is "$", some files will not get deleted.
Therefore, after the first delete, we delete anything left over.  In
real life this almost never occurs, but if it does all that will happen
is that you'll get the "Are you sure (Y/N)?" prompt.
     To enhance this so that you get no error messages if you run it
on an empty directory, IF EXIST clauses may be added to the REN and
DEL commands.
     Editor's Note:  You could erase all the files in a directory with
this ERASE.BAT file:

ECHO OFF
FOR %%F IN (*.*) DO DEL %%F >NUL

     If you omit a carriage return from the end of the second line,
you'll see each file deleted one by one.  However, if you include a
carriage return, while you won't see the individual file deletion
messages, you'll get a "Batch file missing" error message.
     The technique described above is clever, but it won't work
properly since it will delete itself halfway through the process and
grind to a halt.  It's possible to adapt it, with a pair of batch
files.  First, DALL.BAT:

ECHO OFF
MD UPONE
CD UPONE
COPY ..\DELALL.BAT >NUL
COMMAND /C DELALL
CD ..
DEL UPONE\DELALL.BAT
RD UPONE
DEL DALL.BAT

Next, DELALL.BAT:

COPY ..\DALL.BAT >NUL
:START
CTTY NUL
REN ..\*.* $*.*
CTTY CON
DEL ..\$*.*
IF EXIST ..\*.* GOTO START
COPY DALL.BAT .. >NUL
DEL DALL.BAT

     The idea intended here is to create another subdirectory that is
located one level up and copy the batch file in and out, but that's
extremely clunky.  The one real improvement is that if the DELALL.BAT
file does trip over two files that are exactly the same except for the
first letter, it will simply start over again.  DELALL.BAT assumes that
you don't have any files that begin with $.  If you did have such
files, you could also add a third IF statement to rename them to
something else and then delete those -- but the two batch files are
overly complex already.
     Also, be sure to note that >NUL won't suppress error messages,
but CTTY NUL will.  If you use CTTY NUL be very careful to bring your
system back with the command CTTY CON.  And even this technique won't
handle the missing batch file error you'll get if you insert a carriage
return at the end of the last line of DELALL.BAT.
     The obvious solution to this problem is to create a one-line batch
file that you use from one subdirectory to erase all the files in
another subdirectory.  If you're in \1\2\3 and you want to delete
everything in \1\2\3\4, you can do it with the batch file containing
the line:

DEL \1\2\3\4*.* < Y

     For this solution to work you would need a tiny file on \1\2\3
called Y that contained simply two characters -- a Y and a carriage
return.  If you wanted, you could try this with replaceable parameters,
but you'd have to be careful that you didn't erase the wrong files
through a silly but fatal typing error.

-----------------------------------------------------------------
                      Real Batch Variables
       (PC Magazine Vol 6 No 3 Feb 10, 1987 User-to-User)

     DOS can use replaceable parameters in batch files but has no way
to turn replaceable parameters into true variables.  It can be done --
this one works with DOS 3.1 only!
     Use the DEBUG mini-assembler and redirect the INPUT.SCR file:

DEBUG < INPUT.SCR

THis will create a modified version of COMMAND.COM called ALTCOM.COM.
ALTCOM.COM uses the space originally taken up by the VER and RMDIR
commands and replaces these with a new INPUT command.  (You'll still
be able to use RD to remove subdirectories, but not RMDIR.  And VER
will be missing a space or two, as well as its trailing carriage
return.)

N COMMAND.COM
L
A 246E
MOV    SI,3C03
INC    CX
SUB    [SI],CL
MOV    DX,SI
MOV    AX,0C0A
INT    21
INC    SI
DEC    DI
LODSB
MOV    CL,AL
INC    CX
REPZ    MOVSB
CALL    29DG
JMP    270F

E 4D9B "INPUT",02,2E,11
E 4CEB 49
E 4D6D 49
E 4A4E "3.1",00,00,00,00,00,00
N ALTCOM.COM
W
Q

     The syntax for INPUT is:

INPUT variable

When DOS sees the INPUT command in a batch file, it will wait for input
from the keyboard.  This information will then be placed in the DOS
environment for the batch file to use.
     To see this in action, create the following TEST.BAT batch file.
(Remember, this works in DOS 3.1 only.)

ECHO OFF
CLS
:LOOP
ECHO COMMAND?
INPUT CMD=
IF %CMD%! == ! GOTO LOOP
IF %CMD% == STOP GOTO END
IF %CMD% == stop GOTO END
%CMD%
GOTO LOOP
:END

     Before you try it, however, install your new command processor by
typing in ALTCOM at the DOS prompt.  Then run the batch file.  To get
out of the batch file just type STOP (or, stop).
     The number of variables you can use is limited only by the amount
of environment space you have.  If you like this, you can rename
ALTCOM.COM to COMMAND.COM and use it to replace your old command
processor.
     If you type:

SET <parameter1>=<parameter2>

and the name of parameter1 is longer than the environment space, DOS
responds with an "Out of environment space" error.  This is fine but
when you type SET to find out what you have in the environment, you
find the environment contains part of the name of parameter1.  Also
you can no longer set anything else into the environment unless you
erase something previously put in.  Besides, there is no way of
removing that string short of restarting the computer.
     Editor's Note:  This patch is interesting, even though it mangles
some existing commands.  DOS batch files are powerful tools, but users
sorely miss this kind of interaction.  The sample TEST.BAT file above
lets you execute interactive DOS commands on the fly or pass parameters
all around your system.
     If you try this, remember you have to load ALTCOM.COM as a
secondary command processor to make it work (type EXIT to return to
yoru original COMMAND.COM when you're done).
     Finally, in DOS 3.2, you can set environment size, using a
/E COMMAND.COM switch.  And if you're running short of space in your
environment, you can always use the SUBST command to shorten your
paths, which are the big space hogs.

-----------------------------------------------------------------
                    Well-Behaved Batch Files
    (COMPUTE! Magazine February 1987 by Ulf Larsson-Westlund)

     YORN.COM helps make batch files more interactive.  When invoked
from DOS, it displays a yes/no prompt and waits for you to press an
indicated key, returning an error code which the batch file can use
to branch to different parts of the command process.
     To see what YORN.COM does, type YORN at the DOS prompt and press
Enter.  The computer displays the prompt: Answer (Y)es or (N)o ...
and waits for you to indicate your choice.  YORN.COM recognizes only
the characters Y, y, N, or n.
     An example will show how YORN.COM works in this YESNO.BAT file:

ECHO OFF
CLS
:START
ECHO THIS IS A TEST BATCH FILE FOR YORN.COM
YORN PLEAS PRESS N TO CONTINUE ...
IF ERRORLEVEL 255 GOTO WRONG
ECHO
ECHO YOU PRESS THE N KEY
GOTO END
:WRONG
ECHO
ECHO YOU DIDN'T PRESS THE N KEY
GOTO START
:END
ECHO
ECHO ...ENDING

     Type YESNO at the DOS prompt.  Note that YORN.COM displays a
different prompt this time.  Instead of Answer (Y)es or (N)o, it
prints the message PLEASE PRESS N TO CONTINUE.  If you answer "Yes"
by pressing Y or y, one series of batch commands is executed.  If you
answer "No~ by pressing N or n, the batch file branches to a different
series of commands.
     It's not difficult to see how this capability might be useful.
For instance, say you often boot up with an AUTOEXEC.BAT file that
installs an accessory program such as SideKick.  When you use memory-
intensive software such as Framework on a machine with only a limited
amount or RAM, you may find yourself running out of memory if SideKick
or a similar accessory is resident.  With YORN.COM, your AUTOEXEC.BAT
file can ask you whether or not to install the accessory and respond
accordingly.
     YORN.COM tells you which key is pressed by returning an error
code.  In YESNO.BAT, it returns an error code of 255 when you press Y
or y and an error code of 254 for N or n.  You can check the error
code with IF-ERRORLEVEL and branch to the desired destination with
GOTO as shown in the sixth line of YESNO.BAT.  When you're checking
error codes, it is essential to begin with the highest code (255 in
this case) and work downward to lower codes systematically.
     To change the prompt printed by YORN.COM, simply supply the text
of the new prompt after the word YORN in the batch file.  If no such
text is found, YORN.COM prints the default prompt.
     For special purposes, you can also check for characters other
than Y or N.  For instance, a batch process that can send output to
either the screen or a disk file might prompt you to press S for
screen output or D for disk output.
     The hex numbers $59 and $79 in lines 390 and 400 of the BASIC
program stand for the characters Y and y, respectively.  The hex
numbers $4E and $6E in lines 400 and 410 stand for N and n,
respectively.  To substitute other characters, replace these values
with the values of the characters you wish to test for.  Remember that
these numbers must be in hex.  (The BASIC function HEX$ converts
decimal values to hex; for instance, PRINT HEX$(13) displays 0D, the
hex equivalent of decimal 13.)  If you change any of these values, you
must also change the checksum value (10731) in line 170 accordingly.
Once this is done, rerun the BASIC program to create a new version of
YORN.COM.

100 'YORN.BAS:  Creates YORN.COM
120 PRINT "Checking DATA ....";
130 FOR I=0 TO 109
140 READ A$:A=VAL("&H"+A$)
150 CKSUM=CKSUM+A
160 NEXT I
170 IF CKSUM=10731 THEN 210
180 PRINT:PRINT
190 PRINT "Error; check your typing."
200 STOP
210 RESTORE 340
220 OPEN "YORN.COM" AS #1 LEN=1
230 FIELD #1,1 AS BYTE$
240 FOR I=0 TO 109
250 READ A$
260 LSET BYTE$=CHR$(VAL("&H"+A$))
270 PUT #1
280 NEXT I
290 CLOSE #1
300 PRINT:PRINT
310 PRINT "YORN.COM created."
320 PRINT
330 END
340 DATA EB,05,0D,20,20,1A,08,BE,80,00
350 DATA B5,00,8A,0C,83,F9,00,75,0A,BA
360 DATA 54,01,B4,09,CD,21,EB,19,90,46
370 DATA 8A,5C,01,80,FB,0D,74,08,8A,D3
380 DATA B4,02,CD,21,E2,EF,BA,6D,01,B4
390 DATA 09,CD,15,B4,00,CD,16,3C,59,74
400 DATA 11,3C,79,74,0D,3C,4E,74,04,3C
410 DATA 6E,75,EC,B0,FE,EB,03,90,B0,FF
420 DATA B4,4C,CD,21,41,6E,73,77,65,72
430 DATA 20,59,28,65,73,29,20,6F,72,20
440 DATA 4E,28,6F,29,20,2E,2E,2E,24,24

-----------------------------------------------------------------
                       Batch File Bonanza
             (PC World February 1987 Star-Dot-Star)

     DOS lacks an input command that can accept and pass a user's
response to other DOS commands.  If this capability were available,
a batch file could ask the operator if a particular command should
exercise a given option during execution.
     For example, the DIR command can be issued with the /P or /W
option.  With an input command, a batch file could ask if the directory
listing should pause when the screen fills or be displayed in wide
format.  Once the batch file received a response, the DIR command
would execute.
     A DOS input command would also be handy in a batch-file-driven
menu system.  A batch file could display a menu and rely on the input
command to accept and execute the user's choice.
     Until Microsoft includes such a command in its next version of
DOS, you can achieve the same result -- capturing user input -- with
the COPY command.  MENU.BAT is an example of how the technique could
be applied to a menu system.  MENU.BAT begins by changing the DOS
prompt to:

Enter A:MENU to display menu A>

     The program then tests for a parameter and checks whether it's
valid or not.  When you call the batch file without a parameter (by
simply typing:  MENU <Enter>), the first IF test branches execution
to the label :getinput.  The following lines save the current DOS
prompt in a DOS variable called TEMP; use PROMPT to command ANSI.SYS
to redefine the <Enter> key as Ctrl-Z <Enter> and remove the DOS
prompt; clear the screen; and use ECHO commands to display the menu.
(Note that the ANSI.SYS command uses a lowercase p.)  (You must install
the ANSI.SYS driver in your system's CONFIG.SYS file before the PROMPT
command can redefine the keyboard.)
    COPY CON:RESPONSE.DAT creates a file called RESPONSE.DAT containing
the user's response entered from the keyboard.  (Ctrl-Z <Enter> must be
used to inform the COPY command that the response is complete -- hence
the redefined <Enter> key.)  >NUL suppresses the message '1 file(s)
copied' by redirecting it to the nul (nonexistent) device.
     The next COPY command concatenates COMMAND.DAT and RESPONSE.DAT,
creating the file CONTINUE.BAT.  COMMAND.DAT simply contains the word
MENU followed by a space.  Before you run MENU.BAT, create COMMAND.DAT
in the default drive by typing:

COPY CON:COMMAND.DAT <Enter> MENU

and a single space.  Finish up by typing Ctrl-Z and <Enter>.
     With CONTINUE.BAT in place, MENU.BAT uses PROMPT to restore the
<Enter> key's original value, then removes the variable TEMP from the
DOS environment, clears the screen, and calls the file CONTINUE.BAT,
which it just created.
     CONTINUE.BAT issues MENU, along with the user response stored in
RESPONSE.DAT.  MENU.BAT runs anew, and because a parameter is supplied
this time, the first IF test is negative and execution falls to the
next IF test.  When a match is finally found, execution branches to
the appropriate label and the desired menu item is executed.  If there
is no match, MENU.BAT displays the message 'Invalid response'.  Press
a key and the menu reappears, ready for input.

echo off
prompt Enter A:MENU to display menu $_$n$g
cls
if %1!==!    goto getinput
if %1!==1!   goto 1
if %1!==2!   goto 2
if %1!==3!   goto 3
echo Invalid response
pause
:getinput
set temp=%prompt%
prompt $e[13;13;26;13p
echo on
echo off
cls
echo Enter your choice:
echo -
echo 1 for Microsoft Word
echo 2 for Lotus 123
echo 3 for dBASE III
copy con:response.dat >nul
copy command.dat+response.dat continue.bat >nul
prompt $e[13;13p
echo on
echo off
prompt %temp%
set temp=
cls
continue
:1
word
:2
123
:3
dbase

-----------------------------------------------------------------
                        Batch Subroutines
             (PC World February 1987 Star-Dot-Star)

     DOS does not support batch file subroutines -- in other words,
when one batch file calls another, DOS cannot return control to the
first batch file after the second one ends.
     However, you can overcome this limitation by loading a second
copy of COMMAND.COM, the DOS command processor, to execute the second
batch file.  When the second batch file ends, the secondary command
processor returns control to the first.  Execution resumes immediately
after the line in the first batch file that invoked the second
COMMAND.COM.
     This technique is illustrated in CALL.BAT:

echo off
echo This is the first batch file
echo Ready to execute the first subroutine
command/c sub1.bat
echo Now back to the main batch file
echo Transferring control to the second subroutine
command/c sub2.bat
echo Now back to the main batch file again

The first few lines display a message, then COMMAND/C SUB1.BAT executes
the batch file SUB1.BAT:

echo This is the FIRST subroutine batch file
pause

The /C parameter forces DOS to terminate COMMAND.COM when the named
batch file ends.  (If you omit the /C switch, the last line of SUB1.BAT
must be EXIT so that execution can be returned to the primary command
processor; otherwise, commands continue to be processed by the
secondary command processor.)  When SUB1.BAT ends, execution continues
at the fifth line of CALLBAT.BAT, more messages are displayed and
SUB2.BAT:

echo This is the SECOND subroutine batch file
pause

is executed in the same manner.  When SUB2.BAT finishes, control
returns to CALLBAT.BAT, which then ends.
     This technique can be extended -- a second batch file calling a
third, a third a fourth, and so on -- as long as memory is available
and a copy of COMMAND.COM is loaded for each batch file.  Because every
copy of COMMAND.COM creates a new environment, information such as ECHO
status or DOS errorlevel value cannot be passed between batch files.
     By using DOS redirection, a second copy of COMMAND.COM (and any
program run by it) can receive input from a disk file instead of from
the keyboard.  This feature makes it possible to automate virtually
any operation using batch files.

-----------------------------------------------------------------
                        Fast File Scanner
       (PC Magazine Vol 6 No 6 Mar 31, 1987 User-to-User)

     A simple way to display lots of batch files is to create two batch
files called SCANBATS.BAT and READ.BAT.  First, SCANBATS.BAT scans
through all the .BAT files on a disk:

echo off
for %%f in (*.bat) do command /c read %%f

Then, READ.BAT, which is called by SCANBATS.BAT, performs the actual
displaying:

echo off
cls
echo %1
type %1 | more
pause

To try it, type in both files using a pure ASCII word processor or the
DOS COPY CON command, and then type SCANBATS.