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XXCOPY TECHNICAL BULLETIN #22
From: Kan Yabumoto firstname.lastname@example.org
To: XXCOPY user
Subject: The leading backslash in a filespec
Date: 2002-01-03 (revised)
As we see more and more IT professionals who are born after the
WYSIWYG/GUI scheme was invented, certain key concepts which we
took for granted are no longer a commonsense...
xxcopy c:\ d:\ /clone
xxcopy c: d: /clone
If you know the difference of the two lines, just forget this.
But, if you consider the two are about the same, this article
is for you. The difference is subtle and in many cases, the
two lines are the same, indeed. Howerver, in the second line,
the context determines what will be copied and where will be
the destination directory (and what will be deleted from the
Absolute pathspec and Relative pathspec.
The first line of the above example explicitly specifies
that both the source and the destination are the root
directory of respective drives. The second line does not
specify which directory in the source and which directory
of the destination within the respective drives. That is,
the second example above relies the exact location of both
the source and the destination directories on the default
behavior of the OS. Microsoft's OSes keep track of the current
(default) directory on each volume. If it has not been
defined yet, it will go to the root directory (which is what
most users want). Depending on the setting, when you open up
a DOS box, the current (default) directory may or may not be
at the root directory. Also, the current directory of C: may
be at c:\windows whereas on D:, it may be D:\. You just
cannot easily predict what it may be. Therefore, the common
assumption that an unspecified path is equivalent to the root
directory is extremely dangerous with a tool like XXCOPY.
The consequence of the /ZY switch (which is part of the
/CLONE switch) on a wrong source or destination could be quite
FATAL (wipes out all mismatched directories along with their
Let me give you one concrete example. If you run the
The current directory of Volume D: will be set to d:\mydir.
So, unless you change the current (default) directory of
Volume D: back to its root, when you say
xxcopy c:\ d: /clone
Then, the line is equivalent to
xxcopy c:\ d:\mydir /clone
Similarly, when volume C:'s current directory is not at the
root directory (it could be at c:\windows) and you try to copy
xxcopy c: d:\ /clone
In this case, it is equivalent to
xxcopy c:\Windows d:\ /clone
Again, it would give you quite a surprise.
More than one "current" directory:
With the most popular setting of the DOS prompt which usually
shows you the "current directory of the current drive" such as
You don't get any feedback on what is the setting of another
drive. For example, the same example shown above, the console
(the DOS box window)
C:\Windows> cd d:\mydir
When the cd (chdir) command succeeds, there will be no confirming
message. The command is quietly accepted and executed.
Why XXCOPY does not supply the leading backslash for you?
Believe it or not, the way the Absolute pathspec and relative
pathspec are handled throughout the command line environment,
be it DOS, Win32, or even Unix, the convention for the absolute
pathspec and the relative pathspec are so fundamental and
ubiquitous, if we were to implement XXCOPY's own convention
and let XXCOPY implicitly supply the missing leading backslash,
it would create an unbelievable chaos.
Therefore, XXCOPY cannot help you on this, except it prompts
you with an additional warning prompt.
Similar cases everywhere:
The distinction of the absolute and relative path is not limited
to the source and the destination pathspecs. It applies to
any filename you specify in the XXCOPY command line (and also
for most other programs in Windows). For example, we often
hear users complaining about XXCOPY not creating the log file.
You may have a habit of being casual about creating a log file,
XXCOPY c:\src\ d:\dst\ /onmyerror.log
and find no problem. Yet, when you make a batch file using
the same line, you may not find the log file as easily. If you
don't control the "current directory" of the batch file
invocation, you may have a hard time locating the log file.
In Windows (for all the 9x and NT families),
every shortcut object comes with a setting of
the "current directory" (Right-click on the icon
and look for the "Start in" setting). In a case
of a program file or a batch file, the directory
specified in the "Start in" setting becomes the
current directory when the program is executed.
My advice is to spell out the full filespec always:
XXCOPY c:\src\ d:\dst\ /on"C:\My Document\myerror.log"
So, if you are in a position to advise others on how to use
XXCOPY with a concrete example, please do not abbreviate the
leading backslash for cloning a directory. This one-character
difference could be just too great to ignore.
Let me repeat,
PLEASE NEVER USE A SLOPPY COMMAND LINE LIKE THIS
xxcopy c: d: /clone // BAD BAD BAD EXAMPLE!!!
The /CLONE switch is too dangerous to let the system default
setting determine the fate. Instead always specify the
directory using the full (absolute) directory path
xxcopy c:\ d:\ /clone
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