High Voltage Shareware/high1.zip/high1/DIR3/MUF.ZIP/MUF.TXT

Text File | 1993-09-20 | 21KB | 577 lines

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                                 List

                  (MicroSoft's Undocumented Features)

                          Volume 1  Number 5
===============================================================================

1)   TRUENAME

     Internal DOS 5.0 command.  Canonicalize a filename or path (using
     DOS interrupt 21h, function 60) prints the actual directory.

     SYNTAX

     TRUENAME filename      prints the complete path to file

     TRUENAME directory     prints the complete path to directory

     Note: If the path is in a network, it starts with a \\machine-name
                                  Michael Larsson


     TRUENAME is analogous to the "whence" command in the UNIX Korn
     shell.  It returns the real fully qualified pathname for a command.

     TRUENAME is useful in networks, where a physical drive may be mapped
     to a logical volume, and the user needs to know the physical location
     of the file.  It ignores the DOS SUBST, and JOIN commands, or network
     MAPped drives.

     It is an undocumented MS/DOS feature, but is documented in 4DOS as
     follows:

     SYNTAX        (Internal DOS 5.0 / 4DOS)

     TRUENAME [d:][path]filename

     PURPOSE

     Returns a fully qualified filename.

     COMMENTS

     TRUENAME will see "through" JOIN and SUBST commands, and requires
     MS-DOS 3.0 or above.

     EXAMPLE

     The following command uses TRUENAME to get the true pathname for a
     file:

     c:\> subst d: c:\util\test
     c:\> truename d:\test.exe

     c:\util\test\test.exe
                                  Dennis McCunney


     TRUENAME : will reveal the full name drive and path of the filename.
     If you specify a wildcard ('*') in the filename, it will expand
     the filename to use question marks instead. If the path includes
     the ..\ sequence, TRUENAME will examine the directory structure and
     calculate the path.  Stranger still, the line:

         TRUENAME \CRONK\FLIBBET\..\ART
         produces the response:
         C:\CRONK\ART

     even if the directories \CRONK\FLIBBET and the file ART don't exist!
     Don't expect this command to work across networks.
                                  PC Magazine #212 Pg. 48-49
                                  Forwarded by:
                                  Rodney Atkins



2)   FDISK /STATUS ?
     Prints a screen just like using option 4 of fdisk "Partition
     information", but includes extended partition information.
     Nice if you want to get an overview without fear of pressing
     the wrong keys.
                                  Armin Hanisch
     Doesn't work in Ver 3.30.
                                  Mitch Ames
     FDISK /MBR
     MS-DOS 5.0 FDISK has an undocumented parameter, /MBR, that causes it
     to write the master boot record to the hard disk without altering the
     partition table information. While this feature is not documented, it
     can be told to customers on a need-to-know basis.

     Warning: Writing the master boot record to the hard disk in this
     manner can make certain hard disks partitioned with SpeedStor
     unusable. It can also cause problems for some dual-boot programs, or
     for disks with more than 4 partitions.  Specific information is below.

     What is the MBR?
     At the end of the ROM BIOS bootstrap routine, the BIOS will read and
     execute the first physical sector of the first floppy or hard drive on
     the system. This first sector of the hard disk is called the master
     boot record, or sometimes the partition table or master boot block. At
     the beginning of this sector of the hard disk is a small program. At
     the end of this sector is where the partition information, or
     partition table, is stored. This program uses the partition
     information to determine which partition is bootable (usually the
     first primary DOS partition) and attempts to boot from it.

     This program is what is written to the disk by FDISK /MBR and is
     usually called the master boot record.  During normal operation, FDISK
     only writes this program to the disk if there is no master boot
     record.

     Why is the MBR changed during Setup?
     During installation of Microsoft MS-DOS 5 Upgrade, Setup will replace
     the master boot record on the hard disk with code to display the
     message:

        The MS-DOS 5.0 Setup was not completed.
        Insert the UNINSTALL #1 diskette in drive A.
        Press the ENTER key to continue.

     This message should be erased and the master boot code rewritten
     before Setup is completed. If a problem occurs during Setup and you
     return to the previous MS-DOS, UNINSTAL should also remove this
     message. However, should Setup or UNINSTAL fail to remove this
     message, or should the master boot record become corrupted, a new
     master boot record can be written to the disk using the following
     command:
                   C:\>fdisk /mbr

     WARNINGS:
     This option should not be used if:

        - the disk was partitioned using Storage Dimensions' SpeedStor
          utility with its /Bootall option
        - more than 4 partitions exist
        - certain dual-boot programs are in use

     Storage Dimensions' SpeedStor utility using the /Bootall option
     redefines the drive's physical parameters (cylinder, head, sector).
     /BOOTALL stores information on how the drive has been changed in an
     area of the master boot record that MS-DOS does not use. FDISK /MBR
     will erase that information, making the disk unusable.

     Some older OEM versions of MS-DOS and some third-party partitioning
     utilities can create more than 4 partitions.  Additional partition
     information is commonly stored information on partitions in an area
     that FDISK /MBR will overwrite.

     Some dual-boot programs have a special MBR that asks the user which
     operating system they want on bootup.  FDISK /MBR erases this program.
     Dual-boot systems that boot whichever partition is marked Active are
     not affected by FDISK /MBR.
                                  MicroSoft Publication
                                  forwarded by Don Dean

If you have a Boot Sector Virus, just boot from a known "clean" floppy
disk (which has the System files and FDISK on it - IE: your "disaster
recovery disk") and run FDISK /MBR.  Bye, Bye Virus!
                                  Gary Cooper
     Make sure it's write protected ..
                                  Jasen Betts



3)   SHELL=C:\COMMAND.COM /E:1024 /F /P

     The /F in your Config.sys SHELL= statement is another undocumented
     feature.

     It forces a "Fail" response to the "Abort, Retry, Fail" prompt issued
     by the DOS critical error handler.


                                  Dennis McCunney

     COMMAND /F

     Makes all those annoying "Abort, Retry, Ignore, Fail?"
     disk error messages default to "Fail".

                                  Erik Ratcliffe

     For DOS 3.30 (somebody might care to check these for other versions):

     COMMAND /P

        Docs say that this doesn't allow you to exit back to the
        previous shell (ie /Permanent), but /P also forces
        \autoexec.bat to be run on secondary shells.

     COMMAND /D

        (When used with a primary shell, or secondary with /P)
        prevents execution of \autoexec.bat



                                 Mitch Ames


4)   VER/R

     Yields extended information about the OS Version.  IE:

     MS-DOS Version 5.00
     Revision A
     DOS is in HMA

                                  Billy Gilbreath


     Doesn't work with DOS 3.30

                                  Mitch Ames


5)   ECHO OFF     from the command line erases the prompt and leaves
                  just a cursor on the screen.

     ECHO ON      from the command line restores the prompt.

     This works with all version of DOS (tested so far!).

                                  Michael Larsson

Editor's Note:

     One of the most frequently asked questions in the BatPower echo
     is "How do I ECHO a blank line?"  The most common answer is "ECHO."
     However, I have captured a few posts which expand on the
     possibile answers to this request:

     ECHO"

                                  Paul Welsh

    just about any white space character will work.

                                  Alan Newbery

    I just found out myself that any delimiter will work here
    (ECHO. ECHO" ECHO, ECHO: ECHO; ECHO[ ECHO] etc.).  Apparently
    it's just the way that the command handles the delimiter and
    has been available from way back.  Microsoft just began
    mentioning it in the documentation recently, though, and their
    examples use a period.
                                  John Whitfield


6)   FORMAT A: /AUTOTEST
     The autotest parameter will allow format to proceed, checking
     existing format (unless the /u parameter is also present) and
     proceeding with the format.

     All this will take place with no delay and no waiting for user
     input.  It will also end without pausing.  It will not ask for
     a volume label or whether to format another diskette.

     WARNING!  This procedure will also work on hard drives!  Be very
     cautious if you plan to use this feature.
                                  Wayne Woodman

     FORMAT/U is not available in DOS 3.30
                                  Mitch Ames

     FORMAT C: /BACKUP
     This week I've read some articles in Dutch computer magazines about MUF's
     which are very interesting (if you don't already know about them).

     I already knew the FORMAT option /AUTOTEST, but new to me was the
     /BACKUP option.

     EXAMPLE: FORMAT A: /BACKUP

     It seems to work exactly like /AUTOTEST, but it DOES ask for a volume
     label.
                                  Willem Van.den.broek

     FORMAT/SELECT
     is like DOS-Mirror  ... for safety-fanatics only

     FORMAT/SELECT/U
     makes disks unreadable (remember the U)
                                  Reinhard Kujawa
                       Info from The German magazine PC PRAXIS

     FORMAT /H
     In DOS 3.30 (I don't know about other versions), FORMAT /H
     will cause the format to begin immediately after pressing Y
     in response to "Format another?", rather than displaying
     "Place disk to be formatted in drive A: and press Enter" on
     a second and subsequent disks.
                                  Mitch Ames

     On 5.0 it comes back as "invalid switch".
                                  John Mudge


7)   IF EXIST

     IE: IF EXIST EMMXXXX0 GOTO APPLICATION

     This is a handy quirk of DOS - installable drivers are seen as files
     in all directories.  You can use the if exist test to either test for
     the existance of a directory, with "if exist <dirname>\nul", (which
     fails if the directory does not exist because the nul device is not
     found,) or to test whether a driver is loaded.

     Caveats:  you need to know the name of the directory or the driver
     whose existance you are testing, and this is MS/DOS specific - it
     doesn't work on network drives, and may not work under DR-DOS.
                                Gary Marden


     This works definitely under DRDOS:
               DR DOS Version 6.0
               Copyright (c) 1976,1982,1988,1990,1991 Digital Research Inc.
               Alle Rechte vorbehalten.

               C:\>if exist emmxxxx0 echo ja
               ja
                                Wolfram Serber

     Where did you learn the "EMMXXXX0" name from?

     Instead of typing MEM /C, type MEM /D for the "debug" listing.
     That should give the names you're looking for.
                                Erik Ratcliffe

     The trouble is, EXISTS returns TRUE for COM3/4 and LPT2/3 even
     though the hardware does not exist.
                                Rudy Lacchin


8)   ATTRIB

     Is there anyway to create a hidden directory on a hard drive?

     I've since learned that DOS 5.0 ATTRIB can do the same thing
     from the command line:  ATTRIB +h dirname.

                                 Gary Smith


9)   SWITCHES=/W

     Enables you to have your WINA20 file anywhere on your boot
     drive.  Without this you have to have it in the root directory.

                                 Erik Ratcliffe

      You should also mention that this one should not be used with
      Windows 3.1. I've noticed a lot of people who do, and it wastes
      around 120K of UMBs.

                                George Hannah


10)  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


11)    DIR,

       Using a comma IMMEDIATELY after DIR, shows ALL files, including
       the HIDDEN ones.

       EXAMPLE: DIR,

                                Willem van den Broek


       This appears only to work with version 5.  I tried it with 3.30, and
       it didn't display either IO.SYS, MSDOS.SYS (both with S, H and R
       attribs) or a test file with A and H attribs.

       With version 5 it displayed the test file with H and A, but would not
       display IO.SYS or MSDOS.SYS with S, H and R.  This doesn't suprise me
       actually, since S alone (without H) will prevent inclusion of a file
       in a normal DIR.

       I didn't try version 4.

                                Mitch Ames


       Interesting: it (DOS5 display IO.SYS and MSDOS.SYS) does for me:

       However, 4DOS does not do it:

                                Dennis Mccunney


12)    DIR..

       With DOS 6.0 you can get a directory of -all- files (hidden,
       system, etc.) with this command.

       It was in a PC/Mag. or PC/Comp. issue not too long ago.

                                Andrew Barnhardt


13)    COPY. A:

       The use of a decimal point IMMEDIATELY after some DOS statements,
       will replace *.*

       EXAMPLES: DEL.       (erase all files in current directory)
                 COPY. A:   (copy all files in current directory to A:)

       There may be more statements with which it works, but I haven't
       tried them yet.
                                Willem van den Broek

Editor's Note:
       I admit that this is a documented (although obscure feature), the
       reason that it continues to be seen in the MUF list is because
       I believe that the ability to use the period immediately IE: COPY.
       is not documented.  What is documented is the fact that "." and
       ".." can be used to represent the current and parent directories
       respectively, and these will work with many applications which
       can handle directory names as arguements.  In this case the "."
       could also be viewed as a replacement for "*.*"


14)    DOS?=HIGH

       Try "DOS?=HIGH" (with DOS 6.0) and it'll prompt you whether to
       load DOS high or not.
                                  Yousuf Khan


15)    INSTALLHIGH

       I think I may have found an undocumented feature for DOS 6....
       I wasn't able to find this anywhere in the online help.  It's
       called INSTALLHIGH= and amazingly enough it works just like
       INSTALL= but loads the file high!

       The only drawback to this is: Memmaker will not go through and
       add switches for that particular line during the "optimizing
       process".  It just takes it as it is currently.  But then again
       INSTALL= is ignored too!

       Example:
       DEVICE=C:\DOS\HIMEM.SYS
       DEVICE=C:\DOS\EMM386.EXE NOEMS HIGHSCAN WIN=F500-F7FF WIN=F200-F4FF
       dos=HIGH
       dos=UMB
       installhigh=c:\dos\share.exe
                               Robin Francis


16)    : (command)

       DOS uses a leading : to indicate a label.  If the next character
       following the : is a space or other non-alphanumeric char, DOS
       will decide it's an invalid label and skip to the next line,
       performing no further action.
                                Dennis Mccunney


17)    Delimiting Character:

       Prior to DOS 5.0, there was an undocumented DOS function that
       would allow you to set the DOS option delimiter character to
       something else, like -.  Once you did this, you could use either
       \ *or* / in PATH specs.

       DOS 5.0 removed the function to *set* the option delimiter, but
       *retained* the one to query what it currently is!  (Don't ask me,
       ask M'Soft...)  Fortunately, the MKS Toolkit still works with no
       apparent glitches.

       I believe in pre-DOS 3.X versions that there was a parm you could
       provide in CONFIG.SYS to do this, but have no further details.

       Just remember: "undocumented" is a synonym for "unsupported, and
       not guaranteed to be there next release", which is what happened
       in the case I mentioned above.
                                   Dennis Mccunney


18)   REM IN LINES WITH PIPES OR REDIRECTS

      ie:    REM echo y | del *.*

      Michael Serber reported that he encountered problems when
      he tried to REM out an "echo y|del *.*" line in his batch
      file.  Here is the content of some of the responses he
      received in response to his question asking why he experienced
      the problem:

      It (the problem) appears to only occur if there is a pipe or
      redirection in the line (REM'd out), leading me to believe that
      DOS first handles pipes and redirections, then goes back to
      find out what to do with them.
                              John Mudge

     It's actually doing what it thinks you've told it: piping the
     output of REM to DEL.  Since REM _has_ no output (remember
     REM > NULLFILE?), DEL hangs, waiting for the answer to its
     question.
                              Gary Smith

     What is happening here is that DOS reads the entire line, and
     always processes redirection and piping *first*, regardless of
     where they happen to appear.
                              Dennis Mccunney