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Chapter 7.
The X-DOS Batch Language
Introduction
In addition to the internal and external commands detailed in
Chapter 6., X-DOS offers a complete batch language. The batch
language commands can be entered in batch files to allow you to
write simple programs to carry out repetitive tasks. You can
create a batch file containing batch commands in ED, the editor
included with X-DOS and then run this batch file from the command
line.
Files created in this way are called batch files because they
contain a batch of commands, and all such files must have an
extension of .BAT. Each line of a batch file is treated as a
separate command just as if it had been typed in at the command
line. The AUTOEXEC.BAT file is an example of a batch file, though
this is a special file in that X-DOS will always look for this
file each time you boot up your system.
The commands detailed in this chapter are only for use in batch
files and cannot be run directly from the command line. Please
note, however, that the internal and external commands can also
be entered in batch files.
With a little practice you will soon be writing batch files to
prompt for user input, display information on the screen, make
conditional decisions, call other batch files and much more.
7-1
The @ Batch Command
Purpose: This batch command suppresses echoing to the screen
of any command it precedes. The output from a command
preceded by the @ sign is still displayed on the
screen.
Type: Internal to COMMAND.COM
Syntax: @[command] [parameters]
Where: command - is the name of the command you do not want
to display on the screen.
parameters - are any parameters needed by the command
you do not want to display on the screen.
Remarks: Since the ECHO OFF command turns off the display of
all succeeding commands in a batch file, the most
important use of the @ sign is to ensure that the
ECHO OFF command itself does not show on the screen.
The @ sign is also useful in situations where you
want to display the commands that are executed in the
batch file except for maybe one or two commands.
Examples: If you want to ensure that all commands in your batch
file are not displayed on the screen, you normally
want to place the ECHO OFF command as the first line
of your batch file. To make sure that the ECHO OFF
command itself is not displayed on the screen you can
precede it with the @ sign, like this:
@ECHO OFF
ECHO OFF is not displayed on the screen when you run
the batch file.
7-2
The ANSWER Batch Command
Purpose: This batch command prompts you for keyboard input.
Your input is stored in an environment variable named
ANSWER which can later be used by a named
substitution variable from within a batch file or
from any program.
Type: Internal to COMMAND.COM
Syntax: ANSWER [prompt]
Where: prompt - is an optional text string which ANSWER will
display on the screen while waiting for input from
the user.
Remarks: The input you type when ANSWER prompts you is changed
to upper-case before it is assigned to the ANSWER
variable in the environment. You can therefore not
make case dependent tests on ANSWER input.
If the optional prompt is not specified, ANSWER will
not display anything on the screen that will inform
the user that input is expected. Use the ECHO or
REVECHO commands prior to the ANSWER command or use
the optional prompt with ANSWER to make the user
aware that keyboard input is expected.
ANSWER returns an error code which can be examined by
the ERRORLEVEL option of the IF command. The
errorlevel will be set to 0 if the ANSWER variable is
successfully stored in the environment. If there is
insufficient room in the environment to store the
ANSWER variable or if the environment area is
corrupted, ANSWER returns an error code of 1.
You should not use the >, < or | characters in the
ANSWER prompt since they would be interpreted as
redirection symbols.
Examples: In the following example we assume that you have
created a batch file in which you want to prompt the
user for a password before continuing execution of
the batch file. To do this you should include the
following line in your batch file:
ANSWER Enter Your password :
If the user types "SECRET" as his password, the
ANSWER variable is set equal to SECRET in the
environment. To verify this try to make a batch file
which only contains the above line and execute it.
7-3
Then type the password SECRET. When the batch file is
finished executing you can execute the SET command,
like this:
SET
You will see a listing of all current environment
variables. Among them you should see one saying:
ANSWER=SECRET
You can then later use a named environment variable
to use or check the setting of the ANSWER environment
variable. A real batch file in which ANSWER is used
could look similar to this:
ANSWER Please enter your name :
IF %ANSWER%&==& GOTO TOP
ECHO Hello %ANSWER%, how are you today?
You may be wondering about the purpose of the fourth
line of the batch file, IF %ANSWER%&==& GOTO TOP. It
simply checks to see that you have entered any text.
If the ANSWER environment variable is empty, which is
the case if you only press [Enter], the line will be
interpreted by X-DOS like this:
IF &==& GOTO TOP
The & character is only used to ensure that both
sides of the == signs contain information. You do not
have to use the & character.You can actually use any
character just as long as it is the same character on
both sides of the == signs. If the above IF test is
TRUE (&==&) then you know that the ANSWER environment
variable is empty and you can take a proper action.
In the above example we simply go back and prompt the
user to enter his or her name again.
7-4
The BEEP Batch Command
Purpose: This batch command produces a beep on the computer's
speaker which can be used to get the user's attention
during batch file execution.
Type: Internal to COMMAND.COM
Syntax: BEEP
Remarks: This batch command is useful in situations where you
want to make the user aware that input is needed or
an error has occurred.
7-5
The CALL Batch Command
Purpose: This batch command allows one batch file to call
another batch file, execute this batch file, and then
return to the calling batch file and resume execution
right after the CALL command.
Type: Internal to COMMAND.COM
Syntax: CALL [d:][path]filename
Where: d:path - is the drive and path to the batch file you
want to call.
filename - is the name of the batch file you want to
call.
Remarks: The CALL command gives you great flexibility in
setting up modular batch files. This is especially
useful if you are making batch files which will be
executed by different users.
If you do not specify a command from which X-DOS
should continue executing after it returns to the
calling batch file, X-DOS automatically starts
execution from the command following the CALL
command. You can have up to 10 nested CALL commands.
This, in other words, means that you can have one
batch file call another batch file which calls
another batch file, which calls another batch file,
up to 10 nested calls. You can also make recursive
calls which means that a batch file calls itself.
Just remember to ensure that you do not set the batch
file up to run in an endless loop, which can easily
happen if you do not insert some kind of termination
condition.
Examples: We assume that you insert the command:
CALL C:\BATCH\JOHN.BAT
in a batch file. When you execute the batch file, and
X-DOS reaches the CALL command, it will abort the
execution of the current batch file and hand over
control to the JOHN.BAT batch file in the C:\BATCH
directory. When this batch file terminates, X-DOS
will return to the calling batch file and continue
execution right after the CALL C:\BATCH\JOHN.BAT
command.
7-6
The CHECK Batch Command
Purpose: This batch command enhances the batch language by
reporting a variety of parameters that can range from
disk information to time and date functions. Any
results that the CHECK command returns can be
evaluated with the ERRORLEVEL batch sub-command.
Type: Internal to COMMAND.COM
Syntax: CHECK keyword [parameters]
Where: keyword - is one of the keywords which are recognized
by the CHECK command. Each of these keywords are
described below.
parameters - are any parameters which may be required
by the specified keyword.
Remarks: CHECK should come in very handy in automating many of
the mundane tasks you perform. As an example, maybe
you go through and delete all of your *.BAK files the
beginning of every month. You can identify the months
changing by including the CHECK day command in your
batch file. If the day is equal to one (1), it is a
good indication that the month has changed. You can
then branch to your sub-routine for deleting the
*.BAK files.
Disk Related Keywords
DISKSPACE returns the amount of free disk space on the specified
drive, or on the default drive in terms of whole 16K byte blocks.
If there is 120K of free disk space, DISKSPACE returns the value
of 8, which can be used with ERRORLEVEL to indicate 8 blocks are
free.
FILESIZE reports the length of a given file in kilobytes. A value
of 255 means that the file length is 255K or greater in
size.FILEFOUND takes the place of other DOSs IF EXIST conditional
testing and returns a 0 if a file exists and a 1 if it does not
exist.
FILETEXT searches for a text string inside a file. See the
example below:
CHECK filetext C:\DOS\NOTES.MSG `Things to do:'
In the above example, NOTES.MSG is checked for on Drive C: in the
sub-directory \DOS and if present, the string Things to do: is
searched for. If the string is found, a 0 is returned; if not, or
if an error is encountered, such as the file is not on the
specified path, a 1 is returned. You must enclose the string to
7-7
be searched for in single quotes (`').
Hardware Related Keywords
MEMORY - number of 16K memory blocks.
VIDEOTYPE - Monochrome Display Adapter (MGA or Hercules). Color
Graphics Adapter (CGA). Enhanced Graphics Adapter (EGA or VGA).
MATHCO - Math co-processor installed. Math co-processor not
installed.
These options check the hardware configuration. You may have a
program that you keep in two different versions, (i.e. 43 line
format for EGA, and 25 line format for monochrome) and you wish
to know what video card is installed so that you can call the
appropriate configuration. Or, you may have a program installed
for both, with co-processor and without co-processor.
CHECK will identify these things for you and report to your batch
file what it has found.
Miscellaneous Keywords
TIME - returns the current time.
DAY - returns the current day.
MONTH - returns the current month.
KEYPRESS - returns the ASCII code of any key pressed.
Using those keys that produce an extended code like the function
keys and the arrow keys will set the ERRORLEVEL. These keys in
conjunction with X-DOS's KEYIN command, listed elsewhere in this
section, enhance the ability of the batch language to interact
with the user.
Examples: Here are some examples of the options of CHECK, in
everyday use. The following batch file will delete
all .BAK files if free disk space is less than 64K.
CHECK DISKSPACE A:IF NOT ERRORLEVEL 4 DEL A:*.BAK
This batch file will delete a file if it exceeds 16K
in size.
CHECK FILESIZE %1 IF ERRORLEVEL 17 DEL %1
This batch file decides whether to delete a file on
the default drive, based on whether it is present on
another specified drive.
CHECK FILEFOUND B:EXAMPLE.FLE IF ERRORLEVEL 1 DEL C:EXAMPLE.FLE
The following batch file chooses which configuration
7-8
of an installed program to use, based on the video
card that is installed.
CHECK VIDEOTYPE IF ERRORLEVEL 1 GOTO COLORVIDEOWS1GOTO
END:COLORVIDEOWS2:END
7-9
The DELAY Batch Command
Purpose: This batch command lets you delay batch file
processing for a specified amount of time.
Type: Internal to COMMAND.COM
Syntax: DELAY xx
Where: xx - are the number of seconds to delay batch file
processing.
Remarks: The DELAY command is handy when you want to display
important messages that the user should read before
the batch file automatically continues execution.
Examples: If you want to display the message:
Remember to turn off your computer!
and then delay batch file execution for 3 seconds to
allow the user enough time to read the message,
include the following two lines in a batch file:
ECHO Remember to turn off you computer! DELAY 3
7-10
The ECHO Batch Command
Purpose: This batch command is used to display a message on
the screen or to suppress output to the screen.
Type: Internal to COMMAND.COM
Syntax: ECHO [ON | OFF]
or
ECHO [message]
Where: ON - turns ON the display of the commands in a batch
file so that they are displayed on the screen as they
are being executed. ECHO ON is the default setting.
OFF - turns OFF the display of the commands in a
batch file. This way only the output from the
commands that X-DOS executes in the batch file is
displayed.
message - displays a message on the screen. This
message can be up to 127 characters long.
Remarks: The default setting of ECHO ON is very practical when
you are developing a batch file and want to be able
to see which commands are being executed from the
batch file for debugging purposes. Once a batch file
is running flawlessly, there is no longer any reason
to display the commands that are executed from the
batch file. To suppress the display of the commands,
turn the ECHO mode OFF at the beginning of the batch
file.
When the ECHO mode is turned OFF, you can use the
ECHO command to display a message on the screen. The
REVECHO command also displays a message on the screen
in a similar manner, but in reverse video. If you
expect the user to type in an answer to your message
you should use the ANSWER command to display the
message.
If you execute ECHO without any parameters, it will
display the current setting of the ECHO mode, which
is either ON or OFF. If you have turned ECHO mode ON,
you can disable echoing of individual commands by
putting the `@' symbol in front of the command.
Examples: If you want to suppress the display of the commands
that are executed in a batch file, you need to turn
the ECHO mode OFF. To do that you will need to the
following ECHO command at the top of the batch file:
7-11
ECHO OFF
You can view the status of the current ECHO mode by
typing:
ECHO
7-12
The FOR Batch Command
Purpose: This batch command is used in combination with the IN
and DO batch sub-commands to repeat execution of a X-
DOS command or another program.
Type: Internal to COMMAND.COM
Syntax: FOR %%V IN (params) DO command %%V
Where: V - is a one-character substitution variable which
can be other characters than the character 'V' used
here. This variable cannot be a digit (0 to 9) in
order to avoid confusion with the other substitution
variables that can be used in the params section of
the FOR command.
params - is a list of parameters which in turn are
passed to the %%V substitution variable. These
parameters can be any mixture of text strings,
substitution variables, and named substitution
variables.
command - is the name of the command you want to
execute including any necessary parameters that the
command needs.
Remarks: When the FOR command executes it will take each
filespec in params and set it in place of the %%V
substitution variable. If a filespec includes any
wildcards, each filename matching the filespec
replaces the %%V variable one by one.
You will notice that the substitution variable %%V
has two percentage signs (%%) in front of it instead
only one percentage sign (%). The reason for this is
that you want X-DOS to assign values to the
substitution variables of filespecs the first time
around and then assign the values of the substitution
variables of filespecs to the %%V substitution
variable the second time around. Each time X-DOS
assigns values to substitution variables it removes
one percentage sign.
Examples: If you want to create a batch file that can delete
multiple filespecs by issuing only one command, you
can include a FOR command like this:
FOR %%M IN (%1 %2 %3 %4) DO DEL %%M
7-13
The GOTO Batch Command
Purpose: This batch command continues to execute the batch
file a different place as specified by a label name.
Type: Internal to COMMAND.COM
Syntax: GOTO [:]labelname
Where: labelname - is a reference to a label some place in
the batch file. You must specify a colon (:) in front
of a label name in a batch file.
Remarks: The GOTO command instructs X-DOS to jump to a
specific place in a batch file which has the
specified label name assigned to it. A label is any
combination of up to eight alphanumeric characters
and must always be preceded by a colon (:).
References to labels do not need to be preceded by a
colon (:).
The GOTO command is normally used in combination with
the ERRORLEVEL command to branch to another place in
the batch file if a condition is true or not true.
Examples: The following example batch file shows how you can
use the GOTO command:
:STARTIF ERRORLEVEL 5 GOTO EXITECHO HELLOEXIT:
7-14
The IF Batch Command
Purpose: This batch command is used with the EXIST,
ERRORLEVEL, and NOT sub-commands to execute or skip
execution of a command based on a conditional
decision.
Type: Internal to COMMAND.COM
Syntax: IF [NOT] condition command
Where: NOT - means that the command will be executed if the
condition is FALSE.
condition - is one of three possible expressions:
ERRORLEVEL number - makes the condition TRUE if the
program previously executed by COMMAND.COM returned
an exit code equal to , or greater than, number.
string1==string2 - makes the condition TRUE if
string1 equals string2 after a substitution of
substitution variables have occurred. For this
condition to make any sense, one or both of the text
strings have to be a substitution variable.
EXIST [d:][path]filespec - makes the condition TRUE
if a file or range of files exist. You can specify an
optional drive and path to where you want IF to check
for the file(s).
command - is any X-DOS command or other program which
will be executed if the condition is TRUE, or, if the
NOT parameter is specified, is FALSE.
Remarks: Any of the three conditions may be preceded by the
NOT command to indicate that the following command
should be executed only if the condition is not True.
Special care must be taken when comparing two strings
of the form string1==string2 of which one or both of
the strings are named substitution variables. You
must ensure that variables, referenced by string1
and/or string2, have been set up in the environment.
Otherwise, substitution variables without a reference
in the environment are literally going to be
substituted with nothing. Look at the following
example:
IF NOT %TEST%==BAD ECHO Test completed successfully.
If an environment variable named TEST is set to any
7-15
value, the batch file is going to perform as
expected. The ECHO statement is going to be executed
in all instances except when TEST is set to `BAD'.
But, if no variable named TEST is found in the
environment, X-DOS interprets the above command this
way:
IF NOT %TEST%==BAD ECHO Test completed successfully.
Since on TEST variable was found in the environment,
X-DOS substituted %TEST% with absolutely nothing.
When the test is performed, string1 is missing and
you will receive a syntax error. You can avoid this
situation by testing for the existence of the TEST
variable in the environment. A way of doing this is
to make a test similar to this:
IF %TEST%&==& GOTO NO_VAR
By including the '&' character on both sides of the
'==' signs, you ensure that the left side at least
will consist of the '&' character. If this test is
true (&==&) then you know that the environment
variable TEST is missing and you should make the
batch file jump to a place where you give the proper
error message.
Examples: If you want to create a batch file which you want to
use in place of the DEL command to ensure that you do
not accidentally delete files with an extension of
.DOC by using the *.DOC filespec. This file, which we
call NDEL.BAT, could look like this:
IF %1== *.DOC GOTO WARNINGDEL %1 GOTO EXIT:WARNING ECHO You cannot
delete files with the *.DOC filespec!!!:EXIT
7-16
The KEYIN Batch Command
Purpose: This batch command enables you to create interactive
batch files which accept only a predefined set of
keys. This command is especially useful when making
batch file menu systems.
Type: Internal to COMMAND.COM
Syntax: KEYIN A [B C 1 (...)]
Where: A - is any one ASCII character that KEYIN will use
accept before continuing execution of the batch file.
B C 1 - are additional ASCII characters that KEYIN
will accept before continuing execution of the batch
file.
(...) - shows that KEYIN accepts several more ASCII
characters as parameters. You can specify as many
parameters as will fit on the command line and you do
not have to separate the parameters with spaces.
Remarks: The ASCII characters that you use as parameters for
the KEYIN command do not have to be separated by
spaces and each KEYIN parameter can only consist of
one character. KEYIN is not case sensitive and
therefore treats upper- and lower-case letters the
same.
The KEYIN command uses IF ERRORLEVEL testing to check
the input from the user and screen out illegal
entries, meaning any ASCII characters which are not
specified as KEYIN parameters. Any illegal entries
are automatically assigned the exit code 0 and can
therefore be dealt with equally by the author of the
batch file. The first KEYIN parameter is assigned the
exit code 1, the second KEYIN parameter is assigned
the exit code 2, and so forth.
Therefore, when you use IF ERRORLEVEL testing to
check the user's input, you must always put the IF
ERRORLEVEL testing with the highest exit code on top
of the IF ERRORLEVEL testing list since the
ERRORLEVEL command always check for exit codes equal
to or higher than the specified ERRORLEVEL number.
Examples: Suppose the following BATCH file :
:START
ECHO 1. Word Processing
7-17
ECHO 2. Spreadsheet
ECHO 3. Database
ECHO 4. Exit
ECHO INPUT YOUR CHOICE
KEYIN 1234IF ERRORLEVEL 4 GOTO EXIT
IF ERRORLEVEL 3 GOTO DATAB
IF ERRORLEVEL 2 GOTO SPREAD
IF ERRORLEVEL 1 GOTO WP
: WP
....
: SPREAD
....
: DATAB
....
: EXIT
7-18
The LOCATE Batch Command
Purpose: This batch command places the cursor at a specified
location on your screen to allow you to display text
anywhere on the screen.
Type: Internal to COMMAND.COM
Syntax: LOCATE [R][,C]
Where: R - is the screen row in decimal numbers. The upper-
left corner of the screen is row 0 and the screen has
25 or 43 rows.
C - is the screen column in decimal numbers. The
upper-left corner of the screen is column 0 and the
screen has 80 columns.
Remarks: You can use LOCATE with only the Row (R) parameter in
which case the column defaults to column 0. It is
also possible to use the LOCATE command with only the
Column (C) parameter. Just precede the column
parameter with a comma.
7-19
The LOOP Batch Command
Purpose: This batch command can be used to loop part of a
batch file a number of times.
Type: Internal to COMMAND.COM
Syntax: LOOP /IlabelnameLOOP..IF [NOT] ERRORLEVEL number GOTO
labelname
Where: I - sets the loop counter to 0. You should always
initialize the LOOP command before beginning the
actual looping to ensure that it starts counting from
0.
Remarks: The initial LOOP statement with the /I parameter
resets the counter for LOOP. You should always
initialize the LOOP command before beginning the
actual looping. The second LOOP statement actually
performs the loop until a condition is met according
to the ERRORLEVEL checking.
Every time the LOOP command is executed without any
parameters it increases the exit code by one. In your
IF ERRORLEVEL testing you just specify a value which
reflects the number of times you want the loop to be
executed.
Please be aware that IF ERRORLEVEL testing does not support exit
codes above 255, which then is the maximum number of loops you
can perform with one LOOP command.
7-20
The PAUSE Batch Command
Purpose: This batch command stops batch file execution until
the user presses a key. You can optionally specify a
message which will be displayed on the screen when
the PAUSE command is executed.
Type: Internal to COMMAND.COM
Syntax: PAUSE [message]
Where: message - is the message to be displayed while the
PAUSE command waits from input from the user.
Remarks: If no message is entered after PAUSE, the PAUSE
command will display the default message "Press any
key to continue". The user must then press any key at
this point to continue the execution of the batch
file. If you need the user to enter input which is
going to be used later in the batch file you should
use the ANSWER command instead of the PAUSE command.
Examples: If you want to display the message "You have now
completed the installation" on the screen from a
batch file, you can do so by including the following
PAUSE statement:
PAUSE You have now completed the installation
7-21
The REM Batch and Configuration Command
Purpose: Inserts comments or remarks in a batch file
Type: Internal to COMMAND.COM
Syntax: REM [text]
Where: text - is any string of character up to 127 bytes
long
Remarks: When X-DOS encounters a REM command in a batch file
it automatically skips the command and jumps to the
next line in the batch file.You can also use the
colon (:) to insert remarks in your batch file. The
colon is used in batch files to distinguish labels
which are just treated as normal text by X-DOS. Just
ensure that the first word of the remark is not the
name of a valid label that you are already using
elsewhere in the batch file.
Examples: You want to create a batch file which copies multiple
filespecs onto the diskette in the A: drive and you
want to include a remark at the top of the batch file
which explains the purpose of the batch file. Such a
remark could look like this:
REM This batch file copies several filespecs onto a diskette in the A:
drive
REM You must specify the filespecs as parameters to this batch file.
7-22
The REVECHO Batch Command
Purpose: This command is used to display text on the screen in
reverse text.
Type: Internal to COMMAND.COM
Syntax: REVECHO [text]
Where: text - is any string of character up to 127 bytes
long
Remarks: The X-DOS ECHO command provides a simple way to
display messages from within batch files. REVECHO
works the same way, except that it displays the
message in reverse video.
By using REVECHO in combination with the LOCATE
command and the LOOP command, you can make a message
flash on the screen. Since REVECHO looks at the
existing color and reverses it each subsequent time
you execute it, the color will appear to flash if
executed many times in succession.
Examples: A batch file which would flash the message "Warning!"
in the middle of the screen could look similar to
this:
CLS
LOOP /I
:FLASHMES
LOOP>LOCATE 12,35
REVECHO Warning!
IF NOT ERRORLEVEL 100 GOTO FLASHMES
7-23
The SHIFT Batch Command
Purpose: The shift command makes it possible for you to use
more than the standard ten substitution variables, %0
to %9.
Type: Internal to COMMAND.COM
Syntax: SHIFT
Remarks: SHIFT will let you move the value of a substitution
variable down one step at a time (e.g., from %4 to %3
to %2 etc.). When you do this, you will lose the
value of the lowest substitution variable, %0. If you
need to retain a lower value, you can use the SET
command to store the value of the %0 substitution
variable in an environment variable before executing
the SHIFT command.
The SHIFT command can also be used even if you use
less than the maximum ten substitution variables.
Examples: To see how the SHIFT command works we have made a
simple batch file:
REM Test of the SHIFT commandECHO %0 %1 %2SHIFTECHO %0 %1 %2SHIFTECHO
%0 %1 %2
You will need to run this batch file with parameters
from the command line in order to see how it works.
We call this batch file TEST.BAT and execute it with
three parameters, number1, number2, and number3, like
this:
TEST number1 number2 number3
The output to your screen will look like this:
TEST number1 number2number1 number2 number3number2 number3
7-24
