Dos Command Strings STRINGS1.DOC

STRINGS.COM  (Version 1.0)             Copyright (c) 1992 
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            First Published in PC Magazine September 10, 1991 (Utilities)
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This documentation is for STRINGS Version 1.0


STRINGS:
        STRINGS enables batch files to manipulate strings, request and
interpret user input, process files, return system information, and
perform simple math by adding functions to the batch file language.
Stores information in either the local or the master environment.

     Batch files are quick, simple--and frustratingly limited. They can't
ask you questions or interpret your answers. They can't parse a filename,
tell you how much space is left in your environment, or even perform
simple math. Yet despite their shortcomings, a dozen times a day it's to
batch files that we must turn for routine tasks.

     By executing STRINGS.COM from within your batch files, however, you
can make .BAT files do things they could never accomplish on their own.
STRINGS removes many of the restrictions imposed by the limited batch
file vocabulary. For example, you'll be able to perform standard string
manipulations, such as separating a filename from its extension, finding
one string in another, determining the length of a string, and even
reading and writing files.

     STRINGS can store its results in environment variables that other
programs (or subsequent calls to STRINGS) can access. It provides simple
functions that allow batch files to ask a user for input, determine
exactly what he entered, and then pass that input to other programs.
STRINGS even includes simple but effective math functions.

USING STRINGS

     To execute the program, either from within a batch file or from the
DOS prompt, you enter STRINGS, followed by the desired command function
and its necessary parameters. The full syntax is

STRINGS [/?] [/M] [/Pc] [environment var =] FUNCTION [str1][, str2][, str3]

Thus, for example, to return the left 6 characters of a string, you might
enter

             STRINGS LEFT this is a string, 6

     To store the This i result you would simply insert the name of the
destination environment variable, followed by an equal sign, before the
command. Thus, to assign the results of this example in the environment
variable VAR1, your command would be

       STRINGS VAR1 = LEFT This is a stirng, 6

STRINGS would find or create the environment variable VAR1 in the local
environment and assign the value This i to it.

     STRINGS defaults to using the local command-shell environment to
store environment variable results, because that is what batch files use
when substituting strings for environment variables. However, by including
the /M switch before the variable name, you can force STRINGS to use the
system master environment instead of the local command processor
environment. As will be discussed in fuller detail later, you will
use this ability in establishing communications among different DOS
sessions running under Windows.

     Another situation in which the /M switch comes in handy is when you
"shell out" to DOS from within a running program. When a program shells
out to DOS, a copy of COMMAND.COM and the accompanying environment are
created. Any environment variable assignments STRINGS makes during this
shelled session will be lost when you exit from DOS back into the original
program, however. If you want to keep any STRINGS assignments made during
a shelled session, use the /M switch.

     STRINGS provides two additional command line options. The /? switch
simply displays a help list of the STRINGS function commands. These are
shown in the table below - Figure 1.

     The second command line switch is /Pc. Since many strings contain
spaces, by default, STRINGS uses commas instead of spaces to separate
multiple command parameters. If any of the parameter strings themselves
contain commas, however, you can use the /Pc switch to force STRINGS to
employ any unused character as c to differentiate one string from another.
Thus, for example, using /P$ changes the parse character to the dollar
sign ($).

     After a parse character is found, STRINGS scans for the first nonspace
character to begin the next parameter. This process has the effect of
ignoring any leading spaces a parameter may have. To force STRINGS to
respect leading spaces, therefore, STRINGS has been written to interpret
consecutive parse characters as the beginning of a parameter.

     For example, if a string with leading spaces is to be written to a
file, the line

           STRINGS WRITE c:\file.out, ,,  This line has 3 leading spaces

should be used. Without the consecutive commas, STRINGS would begin the
next parameter with the letter T. Using the double parse characters,
STRINGS will not append the commas to the line but will keep the proper
number of spaces in the string before the word  This.

     One additional character requires special handling. DOS uses the
equal sign (=) in assigning a variable name to a value. What happens,
then, if the string parameter you want STRINGS to read into a variable
itself contains an equal sign? You might, for example, want STRINGS to
read the line 

              DEVICE=HIMEN.SYS

from your CONFIG.BAT file and assign this as VAR2.

     STRINGS handles this situation by changing the equal sign character
within the string into the similar-looking but wider ASCII 205 (CDh)
graphics character (=) before assigning the string to an environment
variable. In this example, then, the string actually stored in the
environment would then look like 

                                 VAR2=DEVICE=HIMEN.SYS

     When it reads an environment variable containing the graphics =
character, STRINGS knows to make the reverse substitution of the normal
equal sign. The only thing you need to be aware of is that a program
other than STRINGS will not know about the need to convert the graphics
equal sign back into a regular equal sign in environment variables stored
by STRINGS.

     A final reminder for using STRINGS: DOS limits the length of a program
command line to a maximum of 127 characters. Long strings stored with short
names may run up against this limitation when interpreted.

COMMAND FUNCTIONS

     Several of the STRINGS command functions have been used illustratively
above, but a more systematic description of the complete function set is
in order. The functions can be divided into four main groups: (1) string
manipulation; (2) file operations; (3) system functions; and (4) math
functions.

     (1)   The string manipulation functions start with the LEFT and
RIGHT functions. As shown in the first example, LEFT returns the first n
characters of a string. RIGHT operates similarly: The first parameter
you supply is the string, and the second parameter is the number of
characters you want returned. In both cases, if the string is shorter
than the number you specify, the entire string is returned. If the second
parameter is 0, both functions return a null string.

     Assigning a null string to an environment variable removes the
variable from the environment. For example, if the environment contained
the variable PLAY=1234 and the command

                                       STRINGS PLAY = LEFT abcd, 0

was entered, STRINGS would erase the variable PLAY from the environment. Note
that STRINGS makes no attempt to display null strings on the screen.

     The MID function is used to return a substring starting at any point
within the original string. As with the LEFT and RIGHT commands, the first
parameter you enter is the string itself. The second parameter is the
numerical position of the starting character. The third parameter is the
requested length of the string you want returned. If the starting character
is higher than the length of the string, a null string is returned.

     Not surprisingly, the LENGTH function returns the length of a string.
The only parameter required for this function is the string itself. The
number returned is itself an ASCII string. For example, if a string is 12
characters long, LENGTH returns the number 12 as an ASCII 49 followed by
an ASCII 50.

     The FIND and FINDC functions search a string for a given string of
characters. If the string is found, the number of the starting position
of the string within the original string is returned. FIND searches for
the string without regard to case; FINDC considers case in its search.

     The LOWER and UPPER functions set the case of the string. LOWER
reduces all the characters in a string to lowercase; UPPER capitalizes
a string.

     The CHAR and VAL functions in STRINGS correspond to the CHAR$ and
VAL instructions in BASIC. The CHAR function returns an ASCII character
for the number passed. For example, the STRINGS CHAR 65 command returns
the character A, since 65 is the base 10 ASCII code for the character A.

     The VAL function is the inverse of the CHAR function, it returns the
ASCII number for a character. For example, the VAL B function returns the
number 66.

     (2)   The file operation group of STRINGS functions is best introduced
starting with FILENAME, which parses out the filename from within the
string supplied. For example, the command

                                         STRINGS FILENAME C:\UTIL\EDIT.COM

returns the string EDIT. Similarly, the FILEEXT function returns the file
extension--in this case, COM. If a filename is longer than eight characters,
only the first eight characters are returned; no more than three characters
will be returned by FILEEXT. If the filename cannot be found within the
string or if an illegal filespec is supplied, a null string is returned.

     The file READ and WRITE functions allow batch files to perform
rudimentary file processing. While file processing via a batch file is
obviously slow, it can be useful in some situations.

     The READ function reads a given line from a file. The parameters
you must pass are the filename and the line number within the file to
be read. STRINGS determines line numbers by counting the carriage returns
(13h) in the file, starting with line 1. If an attempt is made to read
either line 0 or a line beyond the end of the file, an error message is
printed and an ERRORLEVEL code of 1 is returned.

     A typical use for the READ function is in parsing the results produced
by piping a find file utility to a file. STRINGS can then be used to read
the filenames (which will each occupy one line) from the file. These
filenames could then be used in conjunction with other DOS commands to
process each of the files individually.

     The WRITE function writes a string to the end of a file. If the file
does not yet exist, it will be created. If the specified file has a
read-only attribute, an error message is printed and an ERRORLEVEL code
of 1 is returned. The WRITE command is functionally identical to the
following batch file command

                             ECHO string >> filename

This command is included in STRINGS to complement the READ command.

     The FILESIZE and LINESIZE functions both return information about
the size of a file. FILESIZE returns the size of a file in bytes;
LINESIZE returns the number of lines in the specified file.

     The TRUENAME function creates a fully specified filename, complete
with drive letter and path. This function corresponds to the undocumented
TRUENAME function available in DOS 4.0 and later. Note that network names
and aliases created from the JOIN, SUBST, and ASSIGN commands are resolved
to produce the actual drive and path. If an illegal filename is passed
to the function, a null string is returned.

     (3)    Five system functions are provided to assist batch files in
determining the system configuration: VER, ASK, ENVFREE, ENVSIZE, and
MASTERVAR.

     The VER function returns a string containing the current DOS version
number. The major version number is reported in the hundreds position,
and the minor version numbers are in the tens and ones places. Called
under DOS 3.3, for example, VER returns the string "330".

     The ASK function allows you to query the user and store his response
as an environment variable. ASK can print a specified prompt string to
the screen; it then waits for the user to respond with up to one line
of input. For example, given the command line

                        STRINGS NAME = ASK What is your name?

      STRINGS will print the string "What is your name?" and then wait
for the user to enter the response and press Enter. The response will
be stored in the environment variable NAME.

     One important application of the ASK function is in accepting piped
output from another DOS command. For example, to create a string
containing the current directory, the following line could be used:

                        CD | STRINGS CURRDIR = ASK

The environment variable CURRDIR would then contain the current directory.

     Since the STRINGS utility depends so heavily on the environment
block, it is only sensible to include the ENVFREE function, which returns
the number of bytes free in the environment. If the /M parameter is used
with this command, ENVFREE returns the bytes free for the master rather
than the local environment.

     The command ENVSIZE returns the total size of the environment block.
This function is useful when a batch file needs a larger environment and
must determine the new size of that environment. As with the ENVFREE
command, ENVSIZE returns the size of the master environment if the /M
switch is used.

     The MASTERVAR function returns the value of an environment variable
from the master environment block. This function allows a user to read a
value from the master environment block and store it in the local command
processor environment block.

     As suggested earlier, one important use for the MASTERVAR function
is in communicating between different DOS sessions running under Windows,
DESQview, or similar programs. This is accomplished by using STRINGS with
the /M switch to assign a value to a variable in the master environment.
Then, when in another DOS session, STRINGS can be used to read the value
of that variable by invoking the MASTERVAR function.

     (4)   To round out STRINGS' capabilities, I've included simple
unsigned arithmetic functions. The ADD function, as you would expect,
sums two (base 10) numbers. The numbers are passed as strings, and the
result is a string containing the sum. The remaining SUB, MUL, and DIV
functions perform as would be expected, taking two numbers as input and
returning the result.

     If an illegal or overlarge number is passed to any of the math
functions, the function is aborted, and a null string is returned. STRINGS
also handles overflows, underflows, and divide by zero errors with the
same null string result. Since STRINGS uses unsigned 32-bit arithmetic,
however, the possible values for numbers range from 0 to a rather hefty
4,294,967,295.

     An additional function of the SUB command should be noted. SUB
responds with an ERRORLEVEL code of 1 if the result is negative. This
enables the function to serve as a useful compare command. For example,
if one of your batch files uses the CALL command--which is available
only under DOS 3.3 and later--you might want to include the following
sequence: 

                 STRINGS ver = VER
                 STRINGS SUB %VER%, 330
                 IF ERRORLEVEL 1 GOTO end
                 CALL NEWFILE.BAT
                 :END

Useful examples of actual batch files that make use of STRINGS are presented
and discussed in the next section.

STRINGS AT WORK

     The test of a utility such as STRINGS is not how good it sounds when
described in an article but how useful it proves in your own batch files.
Presented here, therefore, are some short batch files that use the commands
in STRINGS to perform functions from simple looping to file processing.

      One of the simple things that batch files cannot manage is a FOR
loop with more than one line. LOOP.BAT (see Figure 2 below), is a short
batch file, that uses the ADD function of STRINGS to loop though a
sequence nine times.

     A frequent batch file problem is to determine how a filename was
entered. Did the user type just the filename or was the file extension
included? There is no easy way to parse filenames with standard batch
files, but with STRINGS, it's a piece of cake. PARSE.BAT (see Figure 3 below)
uses STRINGS to parse the filename. This batch file examines the %1 parameter
to see if the user typed the filename on the command line. If not, the ASK
function of STRINGS is used to query the filename from the user.

     Even after the filename has been entered, a problem remains: Does the
filename have an extension?  The FILENAME function of STRINGS is used to
ensure that there is no extension. (If no default extension was placed in
%2, and one wasn't typed by the user, the use is ASKed for an extension.)
Then the extension (either the default or user-entered) is appended with
the DOS SET command.

     Once the filename has been parsed, the DOS IF EXIST command is used
to indicate whether the file actually exists. If the file does not exist,
the .BAT file prints an error message, deletes the environment variable,
and exits. If the file does exist, the environment variable, FNAME, now
contains the correct filename.

      One problem that STRINGS users will soon encounter is the dependence
of the program on available space in the environment. To solve this problem,
a technique demonstrated in the example SHELL.BAT (see Figure 4 below),
can be used.

     SHELL.BAT uses ENVFREE to determine whether enough space exists in
the environment. The SUB command is used to compare the bytes free value
returned by ENVFREE with the required space--in this case 300 bytes.

     The SUB command returns an error code of 1 if the result is negative;
this feature can be used to compare two numbers. The bytes free is subtracted
from the required space. If the bytes free is less than the required space,
an error code of 1 is returned.

     To prevent printing an error message to the screen, the output of
the SUB command is redirected to the NUL device. The IF ERRORLEVEL command
is used to detect the overflow condition.

     If there is enough space, the additional shell statement is not
executed. If more environment space is needed, however, the batch file
determines the required environment size by using ENVSIZE to get the
current environment size and adds the necessary number of bytes.

     The proper command shell is executed by using the COMSPEC environment
variable, whose /E: switch sets the size of the environment of the shell.
The shell statement simply executes the same batch file that was executed
using the %0 command line parameter. Since the new shell will have enough
environment space, the shell statement need only be executed once.

     You've probably often wished that batch files could remember the
current disk and directory. The SETLOCAL and ENDLOCAL commands in OS/2
provide this function, but there is no DOS equivalent. SAVEDIR.BAT (see
Figure 5 below), brings this capability to DOS.

     SAVEDIR uses a combination of piping, redirection, and the STRINGS
ASK commands to put the current disk and directory into the environment
variable OLDDIR. SAVEDIR then changes the disk and directory.

     The LEFT command is used to copy the first two characters from the
string stored in OLDDIR to the variable DRIVE. Since the way to change
the default drive in DOS is by typing the drive letter, a colon, and
then hitting Enter, the variable DRIVE, containing the old disk letter,
is simply executed to return to the proper drive. Return to the correct
directory is achieved by simply using the CD command with the OLDDIR
variable as the argument.

     The final example uses STRINGS to process a file. CAPIT.BAT
(see Figure 6 below), capitalizes the instructions in an assembly file
without disturbing the comments. CAPIT uses a variety of STRINGS
functions, including READ, WRITE, FIND, and UPPER.

     CAPIT first calls PARSE.BAT to parse the input filename correctly.
The output filename is then generated by stripping off the input filename
extension and appending the .OUT extension.

     The main processing loop of CAPIT first reads a line of the input
file into the LINE environment variable. The line is then searched for
a semicolon, which indicates the beginning of a comment. If one is found,
the line is then split into two strings: one containing the characters
before the semicolon, and one containing the characters after. The former
are then capitalized using UPPER and the two lines are rejoined and
written to the output file.

     Note that CAPIT uses the /Pc switch to change the STRINGS parse
character. Assembly files contain commas and therefore commas could not
be used. The character~~************ was used, since it seldom occurs in
assembly language files.

       Note also that in CAPIT, double parse characters are used to
indicate the start of a parameter. In ASM files, lines often begin with
a series of spaces that are important for formatting. The use of the
double parse character immediately before the parameter forces STRINGS
to respect the leading spaces instead of ignoring them.

     Batch files will be about as long as there is a C:> prompt. As you
can see, from these examples, the functions provided by STRINGS can make
your batch files more powerful, easier to write, and even a little more
friendly.

PROGRAMMING NOTES

     Each time STRINGS runs, it must perform three basic steps: parse
the command line, execute the command, and store the result. The job of
parsing the command line is complicated by the fact that the different
STRINGS commands have different required parameters.

     To begin parsing, STRINGS finds the first nonspace character. If the
character is a forward slash (/) the next character is assumed to be a
command line switch. Since there are only two such command line switches,
parsing is done by a simple compare. If a switch is found, the proper
flag is set and the overall parsing continues.

     When a word is found without the switch character prefix, an
interesting problem arises. Is the word a function name or is it the
name of an environment variable? Since there is no way to tell this early
in the routine, STRINGS initially assumes that the word is a command and
copies it into the command buffer.

     The program then scans for the next nonspace character. If that
character is an equal sign (=) then the first word must have been an
environment variable name and not a command function. If so, STRINGS
copies the variable name from the command buffer into the destination
variable name buffer. The equal sign is skipped and the next word is
copied into the command buffer. The CONSOLE OUT flag is cleared to
indicate that the result of the command is to be assigned to an
environment variable. If an equal sign is not found, then the first word
is assumed to be a parameter.

     Command parameters are copied into separate 128-byte buffers.
STRINGS copies a string until the proper parse character (usually the
comma) is found or until the end of the command line is detected.

     If the first two characters in a parameter consist of the parse
character itself, STRINGS skips these characters but starts the parameter
immediately following the parse characters. This allows strings with
leading spaces to be correctly processed.

     After the command line has been parsed, the command must be
validated and the proper routine must be called to execute it. To
validate the command, STRINGS searches through a list of ASCIIZ
strings, each of which is the name of a valid command. The end of
the list is indicated by consecutive zero bytes.

     The format of the command list is the same as the format of a DOS
environment block. This allows the same routine that searches the command
list for valid commands to be used later to search the environment block
for environment variables.

     Once the command name has been found in the list, the index into the
list is used as an index into a jump table. This jump table contains
pointers to each of the routines that implement the commands. The
pointers are then used to call the proper command procedure.

     The command procedures themselves are actually quite simple. Each
procedure accesses the necessary command parameters by loading a pointer
to the proper parameter buffer. The result of the command is stored in
the destination data buffer. The resulting string will later either be
used as the string assigned to the destination environment variable or
it will be printed to the screen as indicated by the syntax of the
command.

     The carry flag is used to indicate an error occurring during
execution of the command. If the carry flag is set, the result is
discarded and the proper error message is printed to the screen. For
all errors, STRINGS terminates with an error code of 1.

     Depending on the state of the CONSOLE OUT flag (set in the command
line parse routine), the result of the command is either printed to the
screen or assigned to an environment variable.

     Before a result can be assigned to an environment variable, however,
the environment must be found. STRINGS can search for either the local
command processor environment or the master environment block.

     Until recently, a second copy of the command processor was only
used when shelling out to DOS from within another program. With the
popularity of programs such as Windows 3.0, secondary command processors
now occur more frequently.

     When Windows creates a DOS session, a second copy of COMMAND.COM is
launched. This second copy of COMMAND.COM creates its own environment,
using the strings stored in the master environment. Thus, when a SET
command is used or an environment variable in a batch file is needed,
it is the secondary environment, not the master environment that is
referenced.

     STRINGS defaults to using the secondary command processor environment.
To find that environment, STRINGS uses an undocumented pointer, located
at offset 16h in the program segment prefix (PSP) block. This pointer
identifies the program that started STRINGS. It is not enough just to
locate STRINGS' parent, however, so STRINGS uses the same pointer in
the parent's PSP to identify its parent. The trace continues until
STRINGS finds a PSP that is its own parent. This is the PSP of COMMAND.COM.

     Even when the COMMAND.COM PSP is found, the job is still not over.
STRINGS cannot use the environment pointer (located at 2Ch) in the
COMMAND.COM PSP, since that points to the environment created for it
when it was first launched. Secondary copies of COMMAND.COM create a
new environment block to use when running, and this is the environment
needed. This new environment is located above the copy of COMMAND.COM,
and STRINGS traces the memory control block chain to find it.

     While searching for the environment of the secondary command
processor is accomplished by tracing the PSP blocks, finding the master
environment involves tracing memory control blocks from the start of
memory. Here the search is complicated by the fact that the rules for
finding the master environment have changed recently.

     Before DOS 4.0, finding the master environment was easy: It was
the first memory block owned by the first installed program in memory.
Finding the segment of the master environment was simply a matter of
tracing the memory allocation blocks to find the first segment owned
by itself, for this indicated that the block contained a PSP. Once found,
the trace continued to find the first block owned by that PSP.

     DOS 4.0 introduced a new wrinkle, because now, by using the INSTALL
keyword in the CONFIG.SYS file, programs can be installed before
COMMAND.COM. Fortunately, however, DOS 4.0 also provides a solution.
Added to the memory control blocks in DOS 4.0 is the name of the program
that owns the block. This allows the trace method to work, modified only
to verify the name of the PSPs found.

     Once the correct environment has been found, STRINGS must still
assign the result to the right variable. The environment is searched for
the variable name, and if it is found, the variable string is removed by
copying the remaining variables over the target variable. The new string,
composed of the environment variable, its value, and the joining equal
sign, is then appended to the end of the environment strings.

     STRINGS checks the size of the environment block to determine
whether the new string will fit. If the block is too small, STRINGS
calls DOS function 4Ah to reallocate memory for the environment block.
If the reallocation call fails, STRINGS terminates with an Out of
Environment Space message.

Douglas Boling is a contributing editor of PC Magazine.

==============================================================================
The table below lists the functions supported by STRINGS, together with
the parameters to supply.

FUNCTION        DESCRIPTION                             PARAMETERS TO SUPPLY

LEFT            Returns left n characters               String, number of
                                                        characters
RIGHT           Returns right n characters              String, number of
                                                        characters
MID             Returns middle n characters             String, starting
                                                        character, length
LENGTH          Returns string length                   String
FIND            Finds position of findstring            String, findstring
FINDC           Case-sensitive FIND                     String, findstring
LOWER           Returns string all lowercase            String
UPPER           Returns string all uppercase            String
CHAR            Returns ASCII value of character        Character

VAL             Returns ASCII character of number       Number

READ            Returns a line from a file              Filename, line number
WRITE           Writes string to end of file            Filename, string
FILESIZE        Returns file size                       Filename
LINESIZE        Returns number of lines                 Filename
FILENAME        Returns filename                        Filespec
FILEEXIT        Returns file extension                  Filespec
TRUENAME        Returns qualified filename              Filename
ASK             Returns user response                   [Prompt string]
VER             Returns the DOS version number
ENVFREE         Returns the bytes free in the 
                environment
ENVSIZE         Returns size of the environment
MASTERVAR       Returns a variable from the
                master environment
ADD             Returns sum of two numbers              Number,number
SUB             Returns difference of two numbers       Number,number
MUL             Returns product of two numbers          Number,number
DIV             Returns quotient of two numbers         Number,number

Figure 1:
========================================================================

LOOP.BAT
------------------
@echo off
REM ===================================================================
REM Loop 10 times using STRINGS to increment a loop variable.
REM ===================================================================

SET count=1
:LABEL1
ECHO %COUNT%
STRINGS count = ADD %COUNT%, 1
IF NOT .%COUNT%==.10 GOTO LABEL1
SET count=

Figure 2:  LOOP.BAT uses STRINGS's ADD function to create a looping
           batch file.
=======================================================================

PARSE.BAT
-------------------
@ECHO off
REM ===================================================================
REM
REM PARSE.BAT - A batch file that parses a filename.
REM
REM Entry: %1 is the filename entered by the user
REM  %2 is the default filename extension desired.
REM
REM Exit:  %FNAME% contains the parsed filename
REM
REM ===================================================================

SET fname=%1
SET fext=%2

IF .%1==. STRINGS fname = ASK Please enter the name of the file

STRINGS fname = FILENAME %fname%

IF .%2==. STRINGS fext = ASK Please enter the extension of the file

STRINGS fname = FILENAME %FNAME%

SET fname=%FNAME%.%FEXT%
IF EXIST %FNAME% GOTO END

ECHO The filename %FNAME% does not exist.
SET fname=
GOTO end

:END
SET fext=

Figure 3:  PARSE.BAT uses the STRINGS utility to parse filenames.
========================================================================

SHELL.BAT
-------------------

@ECHO off
REM ===================================================================
REM
REM Shell out to a new copy of COMMAND.COM to increase environment size
REM
REM ===================================================================

REM
REM Determine the bytes free in the current environment.  If there are not
REM 300 bytes free, shell out to increase the size of the environment.
REM

STRINGS efree = ENVFREE
STRINGS SUB 300, %EFREE% > NUL
IF ERRORLEVEL 1 GOTO main


ECHO Bytes free in current environment:
STRINGS ENVFREE

REM
REM Determine the size of the necessary environment by adding the
REM required bytes to the current environment size.
REM

STRINGS esize = ENVSIZE
STRINGS esize = ADD %ESIZE%, 300

REM
REM Shell out using the COMSPEC variable.  The %0 parameter is the name
REM of the batch file being executed.
REM

%COMSPEC% /e:%ESIZE% /c %0
GOTO end

REM
REM This is the main body of the batch file.  Since this is only an
REM example, the only work done here is to print the number of bytes free
REM in the shelled environment.
REM

:MAIN
ECHO.
ECHO Bytes free in shelled environment
STRINGS ENVFREE

:END
SET EFREE=
SET ESIZE=

Figure 4:  SHELL.BAT can be used to increase environment space.
========================================================================

SAVDIR.BAT
-------------------
@ECHO off
REM ===================================================================
REM
REM Use strings to save the current disk and directory.
REM
REM ===================================================================


REM
REM Pipe the current drive and directory into a env var using the ASK
REM command.
REM

CD | STRINGS olddir = ask > NUL

REM
REM Change to the root directory of the C: drive to leave where we were.
REM

C:
CD \
ECHO on
DIR autoexec.bat
@ECHO off

REM
REM Use the LEFT command to separate the drive letter from the directory
REM string, then change to the proper disk.
REM

STRINGS drive = LEFT %OLDDIR%, 2
%DRIVE%

REM
REM Use the MID command to return the directory string without the drive
REM letter. Change to the proper directory using the CD command.
REM

CD %OLDDIR%

SET drive=
SET olddir=

Figure 5:  SAVEDIR.BAT  saves the current disk and directory.
========================================================================

CAPIT.BAT
-------------------
@ECHO off
REM ===================================================================
REM
REM Use strings to capitalize the opcodes in an ASM file.
REM
REM ===================================================================

REM
REM Use the previous example file PARSE to parse the filename.
REM

CALL PARSE %1 ASM

IF .%fname%==. GOTO end

STRINGS fileout = FILENAME %FNAME%
SET fileout=%FILEOUT%.OUT

SET lnum=1

REM
REM Read the line to the variable 'LINE'.  If no more lines are in the
REM file, STRINGS will return a nonzero return code.  Pipe the output
REM to the NUL driver to avoid the 'Line not found' error message.
REM
:LABEL1

SET line=
SET part1=
SET part2=

STRINGS line = READ %FNAME%, %LNUM% > NUL
IF ERRORLEVEL 1 GOTO end

REM
REM Find the offset of the ; character in the line.  Don't capitalize
REM characters after the ; since they are part of the comment.
REM

STRINGS /p~ offset = FIND ~~%LINE%~ ;
IF .%OFFSET%==.0 SET offset=128

STRINGS /p~ part1 = LEFT ~~%LINE%~ %OFFSET%

STRINGS offset = ADD %OFFSET%, 1

STRINGS /p~ part2 = MID ~~%LINE%~ %OFFSET%~ 128

STRINGS /p~ part1 = UPPER ~~%PART1%

REM
REM Write the line to the file.  Change the parse character to ~ since
REM the line may contain a comma.  Use double parse characters ~~ to
REM force STRINGS to respect any leading spaces in the parameters.
REM

STRINGS /p~ WRITE %FILEOUT%~ ~~%PART1%%PART2% >NUL

STRINGS lnum = ADD %LNUM%, 1

GOTO label1

:END
SET var=
SET fname=
SET fileout=
SET lnum=
SET offset=
SET line=
SET part1=
SET part2=

Figure 6:  CAPIT.BAT improves the readability of assembly language files
           by uppercasing instructions but not comments.
========================================================================

  .