@section Using Cygwin

@subsection Why can't my application locate cygncurses5.dll?  or cygintl.dll?  or cygreadline5.dll?  or ...?

If you upgraded recently, and suddenly vim (or some other Cygwin
application) cannot find @code{cygncurses5.dll}, it means that you did
not follow these instructions properly:
@file{http://cygwin.com/ml/cygwin-announce/2001/msg00124.html}.  To
repair the damage, you must run Cygwin Setup again, and re-install the
@samp{libncurses5} package.

Note that Cygwin Setup won't show this option by default.  In the
``Select packages to install'' dialogue, click on the @samp{Full/Part}
button.  This lists all packages, even those that are already
installed.  Scroll down to locate the @samp{libncurses5} package.
Click on the ``cycle'' glyph until it says ``Reinstall''.  Continue
with the installation.

Similarly, if something cannot find @code{cygintl.dll}, then run
Cygwin Setup and re-install the @samp{libintl} and @samp{libintl1}
packages.

For a detailed explanation of the general problem, and how to extend
it to other missing DLLs (like cygreadline5.dll) and identify their
containing packages, see
@file{http://cygwin.com/ml/cygwin/2002-01/msg01619.html}.

@subsection Why is Cygwin suddenly @emph{so} slow?

If you recently upgraded the @samp{cygwin} package and suddenly
@emph{every} command takes a @emph{very} long time, then you probably
have the obsolete @code{//c} notation in your PATH.  This now means
the @emph{network share} @code{c}, which will slow things down
tremendously if it does not exist.  See then next FAQ entry.

@subsection Why doesn't //c (for C:) work anymore?

(Similarly for any drive letter, e.g. @code{//z} for @code{Z:})

This ``feature'' has long been deprecated, and no longer works at all
in the latest release.  As of release 1.3.3, @code{//c} now means the
@emph{network share} @code{c}.

For a detailed discussion of why this change was made, and how deal
with it now, refer to
@file{http://sources.redhat.com/ml/cygwin/2001-09/msg00014.html}.

@subsection How should I set my PATH?

This is done for you in the file /etc/profile, which is sourced by bash
when you start it from the Desktop or Start Menu shortcut, created by
@code{setup.exe}.  The line is

@example
	PATH="/usr/local/bin:/usr/bin:/bin:$PATH"
@end example

Effectively, this @strong{prepends} /usr/local/bin and /usr/bin to your
Windows system path.  If you choose to reset your PATH, say in
$HOME/.bashrc, or by editing etc/profile directly, then you should
follow this rule.  You @strong{must} have @code{/usr/bin} in your PATH
@strong{before} any Windows system directories.  (And you must not omit
the Windows system directories!)  Otherwise you will likely encounter
all sorts of problems running Cygwin applications.

@subsection Bash says "command not found", but it's right there!

If you compile a program, you might find that you can't run it:

@example
	bash$ gcc -o hello hello.c
        bash$ hello
        bash: hello: command not found
@end example

Unlike Windows, bash does not look for programs in @samp{.} (the current
directory) by default.  You can add @samp{.} to your PATH (see above),
but this is not recommended (at least on UNIX) for security reasons.
Just tell bash where to find it, when you type it on the command line:

@example
	bash$ gcc -o hello hello.c
        bash$ ./hello
        Hello World!
@end example

@subsection How do I convert between Windows and UNIX paths?

Use the 'cygpath' utility.  Type '@code{cygpath --help}' for
information.  For example (on my installation):
@example
	bash$ cygpath --windows ~/.bashrc
        D:\starksb\.bashrc
        bash$ cygpath --unix C:/cygwin/bin/cygwin.bat
        /usr/bin/cygwin.bat
        bash$ cygpath --unix C:\\cygwin\\bin\\cygwin.bat
        /usr/bin/cygwin.bat
@end example
Note that bash interprets the backslash '\' as an escape character, so
you must type it twice in the bash shell if you want it to be recognized
as such.

@subsection Why doesn't bash read my .bashrc file on startup?

Your .bashrc is read from your home directory specified by the HOME
environment variable.  It uses /.bashrc if HOME is not set.  So you need
to set HOME correctly, or move your .bashrc to the top of the drive
mounted as / in Cygwin.

@subsection How can I get bash filename completion to be case insensitive?

Add the following to your @code{~/.bashrc} file:

@example
	shopt -s nocaseglob
@end example

and add the following to your @code{~/.inputrc} file:

@example
	set completion-ignore-case on
@end example

@subsection Can I use paths/filenames containing spaces in them?

Cygwin does support spaces in filenames and paths.  That said, some
utilities that use the library may not, since files don't typically
contain spaces in Unix.  If you stumble into problems with this, you
will need to either fix the utilities or stop using spaces in filenames
used by Cygwin tools.

In particular, bash interprets space as a word separator.  You would have
to quote a filename containing spaces, or escape the space character.
For example:
@example
	bash-2.03$ cd '/cygdrive/c/Program Files'
@end example
or
@example
	bash-2.03$ cd /cygdrive/c/Program\ Files
@end example

@subsection Why can't I cd into a shortcut to a directory?

This is only valid up to but not including version 1.3.0:

Cygwin does not follow MS Windows Explorer Shortcuts (*.lnk files).  It
sees a shortcut as a regular file and this you cannot "cd" into it.

Some people have suggested replacing the current symbolic link scheme
with shortcuts.  The major problem with this is that .LNK files would
then be used to symlink Cygwin paths that may or may not be valid
under native Win32 non-Cygwin applications such as Explorer.

Since version 1.3.0, Cygwin treats shortcuts as symlinks.

@subsection I'm having basic problems with find.  Why?

Make sure you are using the find that came with Cygwin and that you
aren't picking up the Win32 find command instead.  You can verify that
you are getting the right one by doing a "type find" in bash.

If the path argument to find, including current directory (default), is
itself a symbolic link, then find will not traverse it unless you
specify the @samp{-follow} option.  This behavior is different than most
other UNIX implementations, but is not likely to change.

@subsection Where is the @samp{su} command?

The @samp{su} command is not ported to Cygwin, so it is no longer
provided in the distribution.  You may be able to use @samp{login}
instead, but you should read
@file{http://www.cygwin.com/ml/cygwin/2001-03/msg00337.html} first.

If you have a copy of su, then it's from an old Cygwin distribution, and
it probably doesn't work properly anyway.

@subsection Why doesn't man (or apropos) work?

Even after installing the @samp{man} package, you get an error like this:

@example
	bash-2.04$ man man
	Error executing formatting or display command.
	System command (cd /usr/man ; (echo -e ".pl 1100i"; cat /usr/man/man1/man.1; echo ".pl \n(nlu+10") | /usr/bin/tbl | /usr/bin/groff -Tascii -mandoc | less -is) exited with status 32512.
	No manual entry for man
@end example

You also need /bin/sh, which is found in the @samp{ash} package.
You must install this too.

In addition, before you can use @samp{man -k} or @samp{apropos}, you
must create the whatis database.  Just run the command

@example
	/usr/sbin/makewhatis
@end example

(it may take a minute to complete).

@subsection Why doesn't chmod work?

@samp{ntsec} will allow UNIX permissions in Windows NT on NTFS file systems.

@samp{ntea} works on NTFS @emph{and} FAT but it creates a huge,
@strong{undeletable} file on FAT filesystems.

(The @samp{ntsec} and @samp{ntea} settings are values for the
@samp{CYGWIN} environment variable.  See the Cygwin User's Guide at
@file{http://cygwin.com/cygwin-ug-net/cygwin-ug-net.html} for more
information on this variable and its settings.)

There is no solution at all for Windows 9x.

If you have an application that requires a certain permission mode on a
file, you may be able to work around this requirement by modifying the
application's source code.  For a hint, based on work done by Corinna
Vinschen for OpenSSH, see this message from the cygwin mailing list:
@file{http://cygwin.com/ml/cygwin/2000-11/msg01176.html}.

@subsection Why doesn't @samp{mkdir -p} work on a network share?

Unfortunately, you cannot do something like this:

@example
bash$ mkdir -p //MACHINE/Share/path/to/new/dir
mkdir: cannot create directory `//MACHINE': No such file or directory
@end example

This is because mkdir checks for the existence of each directory on the
path, creating them as necessary.  Since @samp{//MACHINE} is not a
directory (you can't cd to it either), mkdir tries to create it, and
fails.

This might get fixed someday, but for now, you have to work around it:

@example
bash$ cd //MACHINE/Share
bash$ mkdir -p path/to/new/dir
@end example

@subsection Why doesn't my shell script work?

There are two basic problems you might run into.  One is the fact that
/bin/sh is really ash, and is missing some features you might expect
in /bin/sh, particularly if you are used to /bin/sh actually being
bash (Linux) or ksh (Tru64).  For example:

@itemize bullet
@item No job control
@item No getopts
@item No let
@item No functions exported
@item Must use `.' instead of `source' (true of sh and ksh too, not just ash)
@end itemize

Or, it could be a permission problem, and Cygwin doesn't understand that
your script is executable.  Because @samp{chmod} may not work (see FAQ
entry above), Cygwin must read the contents of files to determine if
they are executable.  If your script does not start with

@example
	#! /bin/sh
@end example

(or any path to a script interpreter, it does not have to be /bin/sh)
then Cygwin will not know it is an executable script.  The Bourne shell
idiom

@example
	:
	# This is the 2nd line, assume processing by /bin/sh
@end example

also works.

Note that you can use @samp{mount -x} to force Cygwin to treat all files
under the mount point as executable.  This can be used for individual
files as well as directories.  Then Cygwin will not bother to read files
to determine whether they are executable.

@subsection How do I print under Cygwin?

There is no working lp or lpr system as you would find on UNIX.

Jason Tishler has written a couple of messages that explain how to use
a2ps (for nicely formatted text in PostScript) and ghostscript (to print
PostScript files on non-PostScript Windows printers).  Start at
@file{http://cygwin.com/ml/cygwin/2001-04/msg00657.html}.  Note that the
@samp{file} command is now available as part of Cygwin setup.

Alternatively, on NT, you can use the Windows @samp{print} command.  (It
does not seem to be available on Win9x.)  Type

@example
	bash$ print /\?
@end example

for usage instructions (note the @samp{?} must be escaped from the
shell).

Finally, you can simply @samp{cat} the file to the printer's share name:

@example
	bash$ cat myfile > //host/printer
@end example

You may need to press the formfeed button on your printer or append the
formfeed character to your file.

@subsection Why don't international (8-bit) characters work?

Before you can type international characters (£هنِ) in bash, you must
add the following lines to your @code{~/.inputrc} file:

@example
	set meta-flag on 
        set convert-meta off 
        set output-meta on 
@end example

These are options to the @code{readline} library, which you can read
about in the @code{bash(1)} man page.

@subsection Why don't cursor keys work under Win95/Win98?

@strong{(Please note: This section has not yet been updated for the latest
net release.)}

Careful examination shows that they not just non-functional, but
rather behave strangely, for example, with NumLock off, keys on numeric
keyboard work, until you press usual cursor keys, when even numeric
stop working, but they start working again after hitting alphanumeric
key, etc. This reported to happen on localized versions of Win98 and
Win95, and not specific to Cygwin (there're known cases of Alt+Enter
(fullscreen/windowed toggle) not working and shifts sticking with
other programs). The cause of this problem is Microsoft keyboard
localizer which by default installed in 'autoexec.bat'. Corresponding
line looks like:

@example
keyb ru,,C:\WINDOWS\COMMAND\keybrd3.sys
@end example

(That's for russian locale.) You should comment that line if you want
your keys working properly. Of course, this will deprive you of your
local alphabet keyboard support, so you should think about
another localizer. exUSSR users are of course knowledgeable of Keyrus
localizer, and it might work for other locales too, since it has keyboard
layout editor. But it has russian messages and documentation ;-(
Reference URL is http://www.hnet.ru/software/contrib/Utils/KeyRus/
(note the you may need to turn off Windows logo for Keyrus to operate
properly).

@subsection Is it OK to have multiple copies of the DLL?

You should only have one copy of the Cygwin DLL on your system.  If you
have multiple versions, they will conflict and cause problems.

If you get the error "shared region is corrupted" or "shared region
version mismatch" it means you have multiple versions of cygwin1.dll
running at the same time.  This could happen, for example, if you update
cygwin1.dll without exiting @emph{all} Cygwin apps (including inetd)
beforehand.

If you're trying to find multiple versions of the DLL that are causing
this problem, reboot first, in case DLL's still loaded in memory are the
cause.  Then use the Windows System find utility to search your whole
machine, not just components in your PATH (as 'type' would do) or
cygwin-mounted filesystems (as Cygwin 'find' would do).

@subsection Where can I find "more"?

If you are looking for the "more" pager, you should use the "less" pager
instead.

@subsection Why isn't package XXXX available in Cygwin?  (Or, why is your package so out of date?)

Probably because there is nobody willing or able to maintain it.  It
takes time, and the priority for the Cygwin Team is the Cygwin package.
The rest is a volunteer effort.  Want to contribute?  See below.

@subsection How can I access other drives?

You have some flexibility here.

Cygwin has a builtin "cygdrive prefix" for drives that are not mounted.
You can access any drive, say Z:, as '/cygdrive/z/'.

In some applications (notably bash), you can use the familiar windows
<drive>:/path/, using posix forward-slashes ('/') instead of Windows
backward-slashes ('\').  (But see the warning below!)  This maps in the
obvious way to the Windows path, but will be converted internally to use
the Cygwin path, following mounts (default or explicit).  For example:
@example
	bash$ cd C:/Windows
	bash$ pwd
        /cygdrive/c/Windows
@end example
and
@example
	bash$ cd C:/cygwin
	bash$ pwd
        /
@end example
for a default setup.  You could also use backward-slashes in the
Windows path, but these would have to be escaped from the shell.

@strong{Warning:} There is some ambiguity in going from a Windows path
to the posix path, because different posix paths, through different
mount points, could map to the same Windows directory.  This matters
because different mount points may be binmode or textmode, so the
behavior of Cygwin apps will vary depending on the posix path used to
get there.

You can avoid the ambiguity of Windows paths, and avoid typing
"/cygdrive", by explicitly mounting drives to posix paths.  For example:
@example
	bash$ mkdir /c
	bash$ mount c:/ /c
	bash$ ls /c
@end example
Then @samp{/cygdrive/c/Windows} becomes @samp{/c/Windows} which is a
little less typing.

Note that you only need to mount drives once.  The mapping is kept
in the registry so mounts stay valid pretty much indefinitely.
You can only get rid of them with umount, or the registry editor.

The '-b' option to mount mounts the mountpoint in binary mode
("binmode") where text and binary files are treated equivalently.  This
should only be necessary for badly ported Unix programs where binary
flags are missing from open calls.  It is also the setting for /,
/usr/bin and /usr/lib in a default Cygwin installation.  The default for
new mounts is text mode ("textmode"), which is also the mode for all
"cygdrive" mounts.

You can change the default @samp{cygdrive} prefix and whether it is
binmode or textmode using the @code{mount} command.  For example,
@example
	bash$ mount -b --change-cygdrive-prefix cygdrive
@end example
will change all @code{/cygdrive/...} mounts to binmode.

@subsection How can I copy and paste into Cygwin console windows?

Under Windows NT, open the properties dialog of the console window.
The options contain a toggle button, named "Quick edit mode".  It must
be ON.  Save the properties.

Under Windows 9x, open the properties dialog of the console window.
Select the Misc tab.  Uncheck Fast Pasting.  Check QuickEdit.

You can also bind the insert key to paste from the clipboard by adding 
the following line to your .inputrc file: 
@example
	"\e[2~": paste-from-clipboard 
@end example 


@subsection What does "mount failed: Device or resource busy" mean?

@strong{(Please note: This section has not yet been updated for the latest
net release.)}

This usually means that you are trying to mount to a location
already in use by mount.  For example, if c: is mounted as '/'
and you try to mount d: there as well, you will get this error
message.  First "umount" the old location, then "mount" the new one and
you should have better luck.

If you are trying to umount '/' and are getting this message, you may
need to run @code{regedit.exe} and change the "native" key for the '/'
mount in one of the mount points kept under
HKEY_CURRENT_USER/Software/Red Hat, Inc./CYGWIN.DLL setup/<version>
where <version> is the latest registry version associated with the
Cygwin library.

@subsection How can I share files between Unix and Windows?

During development, we have both Unix boxes running Samba and
NT/Windows 95/98 machines.  We often build with cross-compilers
under Unix and copy binaries and source to the Windows system
or just toy with them directly off the Samba-mounted partition.
On dual-boot NT/Windows 9x machines, we usually use the FAT
filesystem so we can also access the files under Windows 9x.

@subsection Are mixed-case filenames possible with Cygwin?

Several Unix programs expect to be able to use to filenames
spelled the same way, but with different case.  A prime example
of this is perl's configuration script, which wants @code{Makefile} and
@code{makefile}.  WIN32 can't tell the difference between files with
just different case, so the configuration fails.

In releases prior to beta 16, mount had a special mixed case option
which renamed files in such a way as to allow mixed case filenames.  We
chose to remove the support when we rewrote the path handling code for
beta 16.  The standard Windows apps -- explorer.exe,
cmd.exe/command.com, etc. -- do not distinguish filenames that differed
only in case, resulting in some (very) undesirable behavior.

Sergey Okhapkin had maintained a mixed-case patch ('coolview') until
about B20.1, but this has not been updated to recent versions of Cygwin.

@subsection What about DOS special filenames?

Files cannot be named com1, lpt1, or aux (to name a few); either as
the root filename or as the extension part.  If you do, you'll have
trouble.  Unix programs don't avoid these names which can make things
interesting.  E.g., the perl distribution has a file called
@code{aux.sh}.  The perl configuration tries to make sure that
@code{aux.sh} is there, but an operation on a file with the magic
letters 'aux' in it will hang.

@subsection When it hangs, how do I get it back?

If something goes wrong and the tools hang on you for some reason (easy
to do if you try and read a file called aux.sh), first try hitting ^C to
return to bash or the cmd prompt.

If you start up another shell, and applications don't run, it's a good
bet that the hung process is still running somewhere.  Use the Task
Manager, pview, or a similar utility to kill the process.

And, if all else fails, there's always the reset button/power switch.
This should never be necessary under Windows NT.

@subsection Why the weird directory structure?

Why do /lib and /usr/lib (and /bin, /usr/bin) point to the same thing?

Why use mounts instead of symbolic links?

Can I use a disk root (e.g., C:\) as Cygwin root?  Why is this discouraged?

After a new installation in the default location, your mount points will
look something like this:

@example
	bash$ mount
	C:\cygwin\bin on /usr/bin type system (binmode)
	C:\cygwin\lib on /usr/lib type system (binmode)
	C:\cygwin on / type system (binmode)
@end example

(Exactly what you see depends on what options you gave to @code{setup.exe}.)

Note that /bin and /usr/bin point to the same location, as do /lib and
/usr/lib.  This is intentional, and you should not undo these mounts
unless you @emph{really} know what you are doing.

Various applications and packages may expect to be installed in /lib or
/usr/lib (similarly /bin or /usr/bin).  Rather than distinguish between
them and try to keep track of them (possibly requiring the occasional
duplication or symbolic link), it was decided to maintain only one
actual directory, with equivalent ways to access it.

Symbolic links had been considered for this purpose, but were dismissed
because they do not always work on Samba drives.  Also, mounts are
faster to process because no disk access is required to resolve them.

Note that non-cygwin applications will not observe Cygwin mounts (or
symlinks for that matter).  For example, if you use WinZip to unpack the
tar distribution of a Cygwin package, it may not get installed to the
correct Cygwin path.  @emph{So don't do this!}

It is strongly recommended not to make the Cygwin root directory the
same as your drive's root directory, unless you know what you are doing
and are prepared to deal with the consequences.  It is generally easier
to maintain the Cygwin hierarchy if it is isolated from, say, C:\.  For
one thing, you avoid possible collisions with other (non-cygwin)
applications that may create (for example) \bin and \lib directories.
(Maybe you have nothing like that installed now, but who knows about
things you might add in the future?)

@subsection How do anti-virus programs like Cygwin?

Users have reported that NAI (formerly McAfee) VirusScan for NT (and
others?) is incompatible with Cygwin.  This is because it tries to scan
the newly loaded shared memory in cygwin1.dll, which can cause fork() to
fail, wreaking havoc on many of the tools.  (It is not confirmed that
this is still a problem, however.)

There have been several reports of NAI VirusScan causing the system to
hang when unpacking tar.gz archives.  This is surely a bug in VirusScan,
and should be reported to NAI.  The only workaround is to disable
VirusScan when accessing these files.  This can be an issue during
setup, and is discussed in that FAQ entry.

Some users report a significant performance hit using Cygwin when their
anti-virus software is enabled.  Rather than disable the anti-virus
software completely, it may be possible to specify directories whose
contents are exempt from scanning.  In a default installation, this
would be @samp{@code{C:\cygwin\bin}}.  Obviously, this could be
exploited by a hostile non-Cygwin program, so do this at your own risk.

@subsection Is there a Cygwin port of GNU Emacs?

Yes!  It uses the X11 (@file{http://cygwin.com/xfree/}) Windows
interface.  From a remote login shell, this ``emacs -nw'' works fine.
There is also a non-X11 version which just provides the text-only
terminal interface.  Use Cygwin Setup to install either one (or both).

@subsection What about NT Emacs?

If you want GNU Emacs with a native Microsoft Windows interface, but
without X, then you must use the native Windows port, commonly known
as ``NT Emacs''.  You get NT Emacs from any GNU mirror.  It is not
available from Cygwin Setup.

NT Emacs uses the Windows command shell by default.  Since it is not a
Cygwin application, it has no knowledge of Cygwin mounts.  With those
points in mind, you need to add the following code to your ~/.emacs
(or ~/_emacs) file in order to use Cygwin bash.  This is particularly useful
for the JDEE package (@file{http://jdee.sunsite.dk/}).  The following
settings are for Emacs 21.1:

@example
	;; This assumes that Cygwin is installed in C:\cygwin (the
	;; default) and that C:\cygwin\bin is not already in your
	;; Windows Path (it generally should not be).
	;;
	(setq exec-path (cons "C:/cygwin/bin" exec-path))
	(setenv "PATH" (concat "C:\\cygwin\\bin;" (getenv "PATH")))
	;;
	;; NT-emacs assumes a Windows command shell, which you change
	;; here.
	;;
	(setq process-coding-system-alist '(("bash" . undecided-unix)))
	(setq shell-file-name "bash")
	(setenv "SHELL" shell-file-name) 
	(setq explicit-shell-file-name shell-file-name) 
	;;
	;; This removes unsightly ^M characters that would otherwise
	;; appear in the output of java applications.
	;;
	(add-hook 'comint-output-filter-functions
	          'comint-strip-ctrl-m)
@end example

If you want NT Emacs to understand Cygwin paths, get
cygwin-mount.el from @file{http://www.emacswiki.org/elisp/index.html}.

Note that all of this ``just works'' if you use the Cygwin port of
Emacs from Cygwin Setup.

@subsection What about XEmacs?

For a concise description of the current situation with XEmacs, see
this message from the Cygwin mailing list:
@file{http://cygwin.com/ml/cygwin/2002-11/msg00609.html}.

@subsection info error "dir: No such file or directory"

Cygwin packages install their info documentation in the /usr/info
directory.  But you need to create a @code{dir} file there before the
standalone info program (probably @code{/usr/bin/info}) can be used to
read those info files.  This is how you do it:
@example
	bash$ cd /usr/info
	bash$ for f in *.info ; do install-info $f dir ; done
@end example
This may generate warnings:
@example
	install-info: warning: no info dir entry in `gzip.info'
	install-info: warning: no info dir entry in `time.info'
@end example
The @code{install-info} command cannot parse these files, so you will
have to add their entries to @code{/usr/info/dir} by hand.

Even if the dir file already exists, you may have to update it when
you install new Cygwin packages.  Some packages update the dir file
for you, but many don't.

@subsection Why do I get a message saying Out of Queue slots?

"Out of queue slots!" generally occurs when you're trying to remove
many files that you do not have permission to remove (either because
you don't have permission, they are opened exclusively, etc).  What
happens is Cygwin queues up these files with the supposition that it
will be possible to delete these files in the future.  Assuming that
the permission of an affected file does change later on, the file will
be deleted as requested.  However, if too many requests come in to
delete inaccessible files, the queue overflows and you get the message
you're asking about.  Usually you can remedy this with a quick chmod,
close of a file, or other such thing.  (Thanks to Larry Hall for
this explanation).

@subsection Why don't symlinks work on samba-mounted filesystems?

Symlinks are marked with "system" file attribute.  Samba does not
enable this attribute by default.  To enable it, consult your Samba
documentation and then add these lines to your samba configuration
file:

@smallexample
	map system = yes
	create mask = 0775
@end smallexample

Note that the 0775 can be anything as long as the 0010 bit is set.

@subsection Why does df report sizes incorrectly.

There is a bug in the Win32 API function GetFreeDiskSpace that
makes it return incorrect values for disks larger than 2 GB in size.
Perhaps that may be your problem?

@subsection Why doesn't Cygwin tcl/tk understand Cygwin paths?

The versions of Tcl/Tk distributed with Cygwin (e.g. cygtclsh80.exe,
cygwish80.exe) are not actually "Cygwin versions" of those tools.
They are built with the @samp{-mno-cygwin} option to @code{gcc}, which
means they do not understand Cygwin mounts or symbolic links.

See the entry "How do I convert between Windows and UNIX paths?"
elsewhere in this FAQ.