11) FOR %%V IN /SOMETHING

    ... quoting Dirk Treusch to All ...

    How can a batch file (without 4DOS) determine from which drive it has
    been started?

    Example: C:\> a:test.bat

    Now my batch should be able to find out that it is located on drive A:
    (not the path - only drive!).

    Mitch Ames responds:

    The variable %0 contains the name of the batch file
    _as_it_was_typed_at_the_command_line.  If you call the batch file as
    A:TEST.BAT, %0 will be "A:TEST.BAT".  If you have the directory on
    your path, and simply type TEST, then %0 will be "TEST".  The drive,
    path and extension will only appear in %0 if you enter them in the
    command used to call the batch file (either typed at the command
    line, or called from another batch file).

    So you _must_ specify the drive as part of the batch filename for
    this to work.  To extract the drive only, use STRINGS, or similar (I
    don't have a copy, so don't ask me to post it).  Alternatively use
    the undocumented FOR %%V in /SOMETHING command, eg:

          set drive=
          for %%v in (/%0) do call test2 %%v
          echo Calling drive is %drive%

    where TEST2.BAT is:

          if not '%drive%'=='' set drive=%1:

    Disclaimer - I haven't tested this.  Debugging is up to you.

    (You can, of course, fit this into a single recursive batch file -
    but that's left as an exercise for the student.)

    FOR %%V IN (/SOMETHING) DO WHATEVER will do WHATEVER twice - the
    first time with %%V set to the first character in SOMETHING ("S"),
    the second time with all the remaining characters in SOMETHING
    ("OMETHING").  If SOMETHING is only a single character, WHATEVER will
    only be called once, with that character in %%V.  If the single
    character is a wildcard (? or *) that wild card will _not_ be
    expanded to a set of filenames.  (The main purpose of this feature is
    apparently to allow inclusion of the literal characters "?" and "*" 
    without them being expanded.)

    This works in DOS 3.30 and 5 - I don't know about other versions.

                              Mitch Ames

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12) LEADING SLASH WITH FOR IN DO LOOP

    In the FOR statement in the INIT and COUNT routines below the
    parameters in the () show a leading "/".  This seems to separate
    the first digit of the environmental variable used within the
    brackets ().  Am I correct? Is this documented anywhere?

    :================= INIT =================
    set &=%4&|set n$=%4|set m$=%3|set #=%2|set !=%0
    if not '%m$%'=='0' for %%a in (/%m$%z) do if '%%a'=='0' set @=0
    %!%
    :================= COUNT ================
    if '%&%'=='&' goto PROCESS
    for %%a in (/%&%) do set &=%%a

                              Peter Joynson
      
    I have read some articles about this in PC Computing & PC Magazine.
    I don't believe it is documented anywhere but you're right, it strips
    off the first character of whatever string is passed.  I will try to
    find one of the articles that explains it better if you need it.

                              Robert Hupf

    Correct.  I believe it is not documented (up to DOS 5 anyway) by MS,
    but I have read from other sources that the leading / will split an
    item into the first character and everything else.  Eg:

            for %%n in (/hello there) do echo %%n

    will display "h", "ello" and "there".  "There" is not split because
    it is a separate item, delimited by the space.  If used with an item
    including wildcard (? or *) characters the item will not be expanded
    to the files which match it, thus allowing inclusion of those
    characters in the set.  Eg:

            for %%n in (/? /*.bat hello) do echo %%n

    will display "?", "*", ".bat", "hello".  This apparently is the
    original reason for the feature, but it may also be used recursively
    to parse a string one character at a time.

                              Mitch Ames
===============================================================================