573 lines
26 KiB
XML
573 lines
26 KiB
XML
<?xml version="1.0" encoding='UTF-8'?>
|
|
<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook V4.5//EN"
|
|
"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
|
|
|
|
<sect1 id="using-pathnames"><title>Mapping path names</title>
|
|
|
|
<sect2 id="pathnames-intro"><title>Introduction</title>
|
|
|
|
<para>Cygwin supports both POSIX- and Win32-style paths. Directory
|
|
delimiters may be either forward slashes or backslashes. Paths using
|
|
backslashes or starting with a drive letter are always handled as
|
|
Win32 paths. POSIX paths must only use forward slashes as delimiter,
|
|
otherwise they are treated as Win32 paths and file access might fail
|
|
in surprising ways.</para>
|
|
|
|
<note><para>The usage of Win32 paths, though possible, is deprecated,
|
|
since it circumvents important internal path handling mechanisms.
|
|
See <xref linkend="pathnames-win32"></xref> and
|
|
<xref linkend="pathnames-win32-api"></xref> for more information.
|
|
</para></note>
|
|
|
|
<para>POSIX operating systems (such as Linux) do not have the concept
|
|
of drive letters. Instead, all absolute paths begin with a
|
|
slash (instead of a drive letter such as "c:") and all file systems
|
|
appear as subdirectories (for example, you might buy a new disk and
|
|
make it be the <filename>/disk2</filename> directory).</para>
|
|
|
|
<para>Because many programs written to run on UNIX systems assume
|
|
the existence of a single unified POSIX file system structure, Cygwin
|
|
maintains a special internal POSIX view of the Win32 file system
|
|
that allows these programs to successfully run under Windows. Cygwin
|
|
uses this mapping to translate from POSIX to Win32 paths as
|
|
necessary.</para>
|
|
|
|
</sect2>
|
|
|
|
<sect2 id="mount-table"><title>The Cygwin Mount Table</title>
|
|
|
|
<para>The <filename>/etc/fstab</filename> file is used to map Win32
|
|
drives and network shares into Cygwin's internal POSIX directory tree.
|
|
This is a similar concept to the typical UNIX fstab file. The mount
|
|
points stored in <filename>/etc/fstab</filename> are globally set for
|
|
all users. Sometimes there's a requirement to have user specific
|
|
mount points. The Cygwin DLL supports user specific fstab files.
|
|
These are stored in the directory <filename>/etc/fstab.d</filename>
|
|
and the name of the file is the Cygwin username of the user, as it's
|
|
created from the Windows account database or stored in the
|
|
<filename>/etc/passwd</filename> file (see
|
|
<xref linkend="ntsec-mapping"></xref>). The structure of the
|
|
user specific file is identical to the system-wide
|
|
<filename>fstab</filename> file.</para>
|
|
|
|
<para>The file fstab contains descriptive information about the various file
|
|
systems. fstab is only read by programs, and not written; it is the
|
|
duty of the system administrator to properly create and maintain this
|
|
file. Each filesystem is described on a separate line; fields on each
|
|
line are separated by tabs or spaces. Lines starting with '#' are
|
|
comments.</para>
|
|
|
|
<para>The first field describes the block special device or
|
|
remote filesystem to be mounted. On Cygwin, this is the native Windows
|
|
path which the mount point links in. As path separator you MUST use a
|
|
slash. Usage of a backslash might lead to unexpected results. UNC
|
|
paths (using slashes, not backslashes) are allowed. If the path
|
|
contains spaces these can be escaped as <literal>'\040'</literal>.</para>
|
|
|
|
<para>The second field describes the mount point for the filesystem.
|
|
If the name of the mount point contains spaces these can be
|
|
escaped as '\040'.</para>
|
|
|
|
<para>The third field describes the type of the filesystem. Cygwin supports
|
|
any string here, since the file system type is usually not evaluated. So it
|
|
doesn't matter if you write <literal>FAT</literal> into this field even if
|
|
the filesystem is NTFS. Cygwin figures out the filesystem type and its
|
|
capabilities by itself.</para>
|
|
|
|
<para>The only exception is the file system type cygdrive. This type is
|
|
used to set the cygdrive prefix. For a description of the cygdrive prefix
|
|
see <xref linkend="cygdrive"></xref></para>
|
|
|
|
<para>The fourth field describes the mount options associated
|
|
with the filesystem. It is formatted as a comma separated list of
|
|
options. It contains at least the type of mount (binary or text) plus
|
|
any additional options appropriate to the filesystem type. Recognized
|
|
options are binary, text, nouser, user, exec, notexec, cygexec, nosuid,
|
|
posix=[0|1]. The meaning of the options is as follows.</para>
|
|
|
|
<screen>
|
|
acl - Cygwin uses the filesystem's access control lists (ACLs) to
|
|
implement real POSIX permissions (default). This flag only
|
|
affects filesystems supporting ACLs (NTFS, for instance) and
|
|
is ignored otherwise.
|
|
auto - Ignored.
|
|
binary - Files default to binary mode (default).
|
|
bind - Allows to remount part of the file hierarchy somewhere else.
|
|
In contrast to other entries, the first field in the fstab
|
|
line specifies an absolute POSIX path. This path is remounted
|
|
to the POSIX path specified as the second path. The conversion
|
|
to a Win32 path is done on the fly. Only the root path and
|
|
paths preceding the bind entry in the fstab file are used to
|
|
convert the POSIX path in the first field to an absolute Win32
|
|
path. Note that symlinks are ignored while performing this path
|
|
conversion.
|
|
cygexec - Treat all files below mount point as cygwin executables.
|
|
dos - Always convert leading spaces and trailing dots and spaces to
|
|
characters in the UNICODE private use area. This allows to use
|
|
broken filesystems which only allow DOS filenames, even if they
|
|
are not recognized as such by Cygwin.
|
|
exec - Treat all files below mount point as executable.
|
|
ihash - Always fake inode numbers rather than using the ones returned
|
|
by the filesystem. This allows to use broken filesystems which
|
|
don't return unambiguous inode numbers, even if they are not
|
|
recognized as such by Cygwin.
|
|
noacl - Cygwin ignores filesystem ACLs and only fakes a subset of
|
|
permission bits based on the DOS readonly attribute. This
|
|
behaviour is the default on FAT and FAT32. The flag is
|
|
ignored on NFS filesystems.
|
|
nosuid - No suid files are allowed (currently unimplemented).
|
|
notexec - Treat all files below mount point as not executable.
|
|
nouser - Mount is a system-wide mount.
|
|
override - Force the override of an immutable mount point (currently "/").
|
|
posix=0 - Switch off case sensitivity for paths under this mount point
|
|
(default for the cygdrive prefix).
|
|
posix=1 - Switch on case sensitivity for paths under this mount point
|
|
(default for all other mount points).
|
|
sparse - Switch on support for sparse files. This option only makes
|
|
sense on NTFS and then only if you really need sparse files.
|
|
Cygwin does not try to create sparse files by default for
|
|
performance reasons.
|
|
text - Files default to CRLF text mode line endings.
|
|
user - Mount is a user mount.
|
|
</screen>
|
|
|
|
<para>While normally the execute permission bits are used to evaluate
|
|
executability, this is not possible on filesystems which don't support
|
|
permissions at all (like FAT/FAT32), or if ACLs are ignored on filesystems
|
|
supporting them (see the aforementioned <literal>acl</literal> mount option).
|
|
In these cases, the following heuristic is used to evaluate if a file is
|
|
executable: Files ending in certain extensions (.exe, .com, .bat, .btm,
|
|
.cmd) are assumed to be executable. Files whose first two characters begin
|
|
with '#!' are also considered to be executable.
|
|
The <literal>exec</literal> option is used to instruct Cygwin that the
|
|
mounted file is "executable". If the <literal>exec</literal> option is used
|
|
with a directory then all files in the directory are executable.
|
|
This option allows other files to be marked as executable and avoids the
|
|
overhead of opening each file to check for a '#!'. The
|
|
<literal>cygexec</literal> option is very similar to <literal>exec</literal>,
|
|
but also prevents Cygwin from setting up commands and environment variables
|
|
for a normal Windows program, adding another small performance gain. The
|
|
opposite of these options is the <literal>notexec</literal> option, which
|
|
means that no files should be marked as executable under that mount point.</para>
|
|
<para>A correct root directory is quite essential to the operation of
|
|
Cygwin. A default root directory is evaluated at startup so a
|
|
<filename>fstab</filename> entry for the root directory is not necessary.
|
|
If it's wrong, nothing will work as expected. Therefore, the root directory
|
|
evaluated by Cygwin itself is treated as an immutable mount point and can't
|
|
be overridden in /etc/fstab... unless you think you really know what you're
|
|
doing. In this case, use the <literal>override</literal> flag in the options
|
|
field in the <filename>/etc/fstab</filename> file. Since this is a dangerous
|
|
thing to do, do so at your own risk.</para>
|
|
|
|
<para><filename>/usr/bin</filename> and <filename>/usr/lib</filename> are
|
|
by default also automatic mount points generated by the Cygwin DLL similar
|
|
to the way the root directory is evaluated. <filename>/usr/bin</filename>
|
|
points to the directory the Cygwin DLL is installed in,
|
|
<filename>/usr/lib</filename> is supposed to point to the
|
|
<filename>/lib</filename> directory. This choice is safe and usually
|
|
shouldn't be changed. An fstab entry for them is not required.</para>
|
|
|
|
<para><literal>nouser</literal> mount points are not overridable by a later
|
|
call to <command>mount</command>.
|
|
Mount points given in <filename>/etc/fstab</filename> are by default
|
|
<literal>nouser</literal> mount points, unless you specify the option
|
|
<literal>user</literal>. This allows the administrator to set certain
|
|
paths so that they are not overridable by users. In contrast, all mount
|
|
points in the user specific fstab file are <literal>user</literal> mount
|
|
points.</para>
|
|
|
|
<para>The fifth and sixth field are ignored. They are
|
|
so far only specified to keep a Linux-like fstab file layout.</para>
|
|
|
|
<para>Note that you don't have to specify an fstab entry for the root dir,
|
|
unless you want to have the root dir pointing to somewhere entirely
|
|
different (hopefully you know what you're doing), or if you want to
|
|
mount the root dir with special options (for instance, as text mount).</para>
|
|
|
|
<para>Example entries:</para>
|
|
|
|
<itemizedlist spacing="compact">
|
|
<listitem>
|
|
<para>Just a normal mount point:</para>
|
|
<screen> c:/foo /bar fat32 binary 0 0</screen>
|
|
</listitem>
|
|
<listitem>
|
|
<para>A mount point for a textmode mount with case sensitivity switched off:</para>
|
|
<screen> C:/foo /bar/baz ntfs text,posix=0 0 0</screen>
|
|
</listitem>
|
|
<listitem>
|
|
<para>A mount point for a Windows directory with spaces in it:</para>
|
|
<screen> C:/Documents\040and\040Settings /docs ext3 binary 0 0</screen>
|
|
</listitem>
|
|
<listitem>
|
|
<para>A mount point for a remote directory, don't store POSIX permissions in ACLs:</para>
|
|
<screen> //server/share/subdir /srv/subdir smbfs binary,noacl 0 0</screen>
|
|
</listitem>
|
|
<listitem>
|
|
<para>This is just a comment:</para>
|
|
<screen> # This is just a comment</screen>
|
|
</listitem>
|
|
<listitem>
|
|
<para>Set the cygdrive prefix to /mnt:</para>
|
|
<screen> none /mnt cygdrive binary 0 0</screen>
|
|
</listitem>
|
|
<listitem>
|
|
<para>Remount /var to /usr/var:</para>
|
|
<screen> /var /usr/var none bind</screen>
|
|
<para>Assuming <filename>/var</filename> points to
|
|
<filename>C:/cygwin/var</filename>, <filename>/usr/var</filename> now
|
|
also points to <filename>C:/cygwin/var</filename>. This is equivalent
|
|
to the Linux <literal>bind</literal> option available since
|
|
Linux 2.4.0.</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
|
|
<para>Whenever Cygwin generates a Win32 path from a POSIX one, it uses
|
|
the longest matching prefix in the mount table. Thus, if
|
|
<filename>C:</filename> is mounted as <filename>/c</filename> and also
|
|
as <filename>/</filename>, then Cygwin would translate
|
|
<filename>C:/foo/bar</filename> to <filename>/c/foo/bar</filename>.
|
|
This translation is normally only used when trying to derive the
|
|
POSIX equivalent current directory. Otherwise, the handling of MS-DOS
|
|
filenames bypasses the mount table.
|
|
</para>
|
|
|
|
<para>If you want to see the current set of mount points valid in your
|
|
session, you can invoke the Cygwin tool <command>mount</command> without
|
|
arguments:</para>
|
|
|
|
<example id="pathnames-mount-ex">
|
|
<title>Displaying the current set of mount points</title>
|
|
<screen>
|
|
<prompt>bash$</prompt> <userinput>mount</userinput>
|
|
f:/cygwin/bin on /usr/bin type ntfs (binary,auto)
|
|
f:/cygwin/lib on /usr/lib type ntfs (binary,auto)
|
|
f:/cygwin on / type ntfs (binary,auto)
|
|
e:/src on /usr/src type vfat (binary)
|
|
c: on /cygdrive/c type ntfs (binary,posix=0,user,noumount,auto)
|
|
e: on /cygdrive/e type vfat (binary,posix=0,user,noumount,auto)
|
|
</screen>
|
|
</example>
|
|
|
|
<para>You can also use the <command>mount</command> command to add
|
|
new mount points, and the <command>umount</command> to delete
|
|
them. However, since they are only stored in memory, these mount
|
|
points will disappear as soon as your last Cygwin process ends.
|
|
See <xref linkend="mount"></xref> and <xref linkend="umount"></xref> for more
|
|
information.</para>
|
|
|
|
<note><para>
|
|
When you upgrade an existing older Cygwin installation to Cygwin 1.7,
|
|
your old system mount points (stored in the HKEY_LOCAL_MACHINE branch
|
|
of your registry) are read by a script and the <filename>/etc/fstab</filename>
|
|
file is generated from these entries. Note that entries for
|
|
<filename>/</filename>, <filename>/usr/bin</filename>, and
|
|
<filename>/usr/lib</filename> are <emphasis role='bold'>never</emphasis>
|
|
generated.
|
|
</para>
|
|
|
|
<para>
|
|
The old user mount points in your HKEY_CURRENT_USER branch of the registry
|
|
are not used to generate <filename>/etc/fstab</filename>. If you want
|
|
to create a user specific <filename>/etc/fstab.d/${USER}</filename> file
|
|
from your old entries, there's a script available which does exactly
|
|
that for you, <filename>/bin/copy-user-registry-fstab</filename>. Just
|
|
start the script and it will create your user specific fstab file. Stop
|
|
all your Cygwin processes and restart them, and you can simply use your
|
|
old user mount points as before.
|
|
</para></note>
|
|
|
|
</sect2>
|
|
|
|
<sect2 id="unc-paths"><title>UNC paths</title>
|
|
|
|
<para>Apart from the unified POSIX tree starting at the <filename>/</filename>
|
|
directory, UNC pathnames starting with two slashes and a server name
|
|
(<filename>//machine/share/...</filename>) are supported as well.
|
|
They are handled as POSIX paths if only containing forward slashes. There's
|
|
also a virtual directory <filename>//</filename> which allows to enumerate
|
|
the fileservers known to the local machine with <command>ls</command>.
|
|
Same goes for the UNC paths of the type <filename>//machine</filename>,
|
|
which allow to enumerate the shares provided by the server
|
|
<literal>machine</literal>. For often used UNC paths it makes sense to
|
|
add them to the mount table (see <xref linkend="mount-table"></xref> so
|
|
they are included in the unified POSIX path tree.</para>
|
|
|
|
</sect2>
|
|
|
|
<sect2 id="cygdrive"><title>The cygdrive path prefix</title>
|
|
|
|
<para>As already outlined in <xref linkend="ov-hi-files"></xref>, you can
|
|
access arbitary drives on your system by using the cygdrive path prefix.
|
|
The default value for this prefix is <filename>/cygdrive</filename>, and
|
|
a path to any drive can be constructed by using the cygdrive prefix and
|
|
appending the drive letter as subdirectory, like this:</para>
|
|
|
|
<screen>
|
|
bash$ ls -l /cygdrive/f/somedir
|
|
</screen>
|
|
|
|
<para>This lists the content of the directory F:\somedir.</para>
|
|
|
|
<para>The cygdrive prefix is a virtual directory under which all drives
|
|
on a system are subsumed. The mount options of the cygdrive prefix is
|
|
used for all file access through the cygdrive prefixed drives. For instance,
|
|
assuming the cygdrive mount options are <literal>binary,posix=0</literal>,
|
|
then any file <filename>/cygdrive/x/file</filename> will be opened in
|
|
binary mode by default (mount option <literal>binary</literal>), and the case
|
|
of the filename doesn't matter (mount option <literal>posix=0</literal>).
|
|
</para>
|
|
|
|
<para>The cygdrive prefix flags are also used for all UNC paths starting with
|
|
two slashes, unless they are accessed through a mount point. For instance,
|
|
consider these <filename>/etc/fstab</filename> entries:</para>
|
|
|
|
<screen>
|
|
//server/share /mysrv ntfs posix=1,acl 0 0
|
|
none /cygdrive cygdrive posix=0,noacl 0 0
|
|
</screen>
|
|
|
|
<para>Assume there's a file <filename>\\server\share\foo</filename> on the
|
|
share. When accessing it as <filename>/mysrv/foo</filename>, then the flags
|
|
<literal>posix=1,acl</literal> of the /mysrv mount point are used. When
|
|
accessing it as <filename>//server/share/foo</filename>, then the flags
|
|
for the cygdrive prefix, <literal>posix=0,noacl</literal> are used.</para>
|
|
|
|
<note><para>This only applies to UNC paths using forward slashes. When
|
|
using backslashes the flags for native paths are used. See
|
|
<xref linkend="pathnames-win32"></xref>.</para></note>
|
|
|
|
<para>The cygdrive prefix may be changed in the fstab file as outlined above.
|
|
Please note that you must not use the cygdrive prefix for any other mount
|
|
point. For instance this:</para>
|
|
|
|
<screen>
|
|
none /cygdrive cygdrive binary 0 0
|
|
D: /cygdrive/d somefs text 0 0
|
|
</screen>
|
|
|
|
<para>will not make file access using the /mnt/d path prefix suddenly using
|
|
textmode. If you want to mount any drive explicitly in another mode than
|
|
the cygdrive prefix, use a distinct path prefix:</para>
|
|
|
|
<screen>
|
|
none /cygdrive cygdrive binary 0 0
|
|
D: /mnt/d somefs text 0 0
|
|
</screen>
|
|
|
|
</sect2>
|
|
|
|
<sect2 id="pathnames-symlinks"><title>Symbolic links</title>
|
|
|
|
<para>Symbolic links are not present and supported on Windows until Windows
|
|
Vista/Server 2008, and then only on some filesystems. Since POSIX applications
|
|
are rightfully expecting to use symlinks and the
|
|
<literal>symlink(2)</literal> system call, Cygwin had to find a
|
|
workaround for this Windows flaw.</para>
|
|
|
|
<para>Cygwin creates symbolic links potentially in multiple different
|
|
ways:</para>
|
|
|
|
<itemizedlist mark="bullet">
|
|
|
|
<listitem>
|
|
<para>The default symlinks are plain files containing a magic cookie
|
|
followed by the path to which the link points. They are marked with the
|
|
DOS SYSTEM attribute so that only files with that attribute have to be
|
|
read to determine whether or not the file is a symbolic link.</para>
|
|
|
|
<note><para>Starting with Cygwin 1.7, symbolic links are using UTF-16 to encode
|
|
the filename of the target file, to better support internationalization.
|
|
Symlinks created by older Cygwin releases can be read just fine. However,
|
|
you could run into problems with them if you're now using another character
|
|
set than the one you used when creating these symlinks
|
|
(see <xref linkend="setup-locale-problems"></xref>). Please note that this
|
|
new UTF-16 style of symlinks is not compatible with older Cygwin release,
|
|
which can't read the target filename correctly.</para></note>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>The shortcut style symlinks are Windows <literal>.lnk</literal>
|
|
shortcut files with a special header and the DOS READONLY attribute set.
|
|
This symlink type is created if the environment variable
|
|
<literal>CYGWIN</literal> (see <xref linkend="using-cygwinenv"></xref>)
|
|
is set to contain the string <literal>winsymlinks</literal> or
|
|
<literal>winsymlinks:lnk</literal>. On the MVFS filesystem, which does
|
|
not support the DOS SYSTEM attribute, this is the one and only supported
|
|
symlink type, independently from the <literal>winsymlinks</literal>
|
|
setting.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>Native Windows symlinks are only created on Windows Vista/2008 and later,
|
|
and only on filesystems supporting reparse points. Due to to their weird
|
|
restrictions and behaviour, they are only created if the user
|
|
explicitely requests creating them. This is done by setting the
|
|
environment variable <literal>CYGWIN</literal> to contain the string
|
|
<literal>winsymlinks:native</literal> or
|
|
<literal>winsymlinks:nativestrict</literal>. For the difference between
|
|
these two settings, see <xref linkend="using-cygwinenv"></xref>.
|
|
On AFS, native symlinks are the only supported type of symlink due to
|
|
AFS lacking support for DOS attributes. This is independent from the
|
|
<literal>winsymlinks</literal> setting.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>On the NFS filesystem, Cygwin always creates real NFS symlinks.</para>
|
|
</listitem>
|
|
|
|
</itemizedlist>
|
|
|
|
<para>All of the above four symlink types are recognized and used as symlinks
|
|
under all circumstances. However, if the default plain file symlink type
|
|
is lacking its DOS SYSTEM bit, or if the shortcut file is lacking the DOS
|
|
READONLY attribute, they are not recognized as symlink.</para>
|
|
|
|
<para>Apart from these four types, there's also a fifth type, which is
|
|
recognized as symlink but never generated by Cygwin, directory
|
|
junctions. This is an older reparse point type, supported by Windows
|
|
since Windows 2000. Filesystem junctions on the other hand are not
|
|
handled as symlinks, since otherwise they would not be recognized as
|
|
filesystem borders by commands like <command>find -xdev</command>.</para>
|
|
|
|
</sect2>
|
|
|
|
<sect2 id="pathnames-win32"><title>Using native Win32 paths</title>
|
|
|
|
<para>Using native Win32 paths in Cygwin, while possible, is generally
|
|
inadvisable. Those paths circumvent all internal integrity checking and
|
|
bypass the information given in the Cygwin mount table.</para>
|
|
|
|
<para>The following paths are treated as native Win32 paths in Cygwin:</para>
|
|
|
|
<itemizedlist spacing="compact">
|
|
<listitem>
|
|
<para>All paths starting with a drive specifier</para>
|
|
<screen>
|
|
C:\foo
|
|
C:/foo
|
|
</screen>
|
|
</listitem>
|
|
<listitem>
|
|
<para>All paths containing at least one backslash as path component</para>
|
|
<screen>
|
|
C:/foo/bar<emphasis role='bold'>\</emphasis>baz/...
|
|
</screen>
|
|
</listitem>
|
|
<listitem>
|
|
<para>UNC paths using backslashes</para>
|
|
<screen>
|
|
\\server\share\...
|
|
</screen>
|
|
</listitem>
|
|
</itemizedlist>
|
|
|
|
<para>When accessing files using native Win32 paths as above, Cygwin uses a
|
|
default setting for the mount flags. All paths using DOS notation will be
|
|
treated as case insensitive, and permissions are just faked as if the
|
|
underlying drive is a FAT drive. This also applies to NTFS and other
|
|
filesystems which usually are capable of case sensitivity and storing
|
|
permissions.</para>
|
|
|
|
</sect2>
|
|
|
|
<sect2 id="pathnames-win32-api"><title>Using the Win32 file API in Cygwin applications</title>
|
|
|
|
<para>Special care must be taken if your application uses Win32 file API
|
|
functions like <function>CreateFile</function> to access files using
|
|
relative pathnames, or if your application uses functions like
|
|
<function>CreateProcess</function> or <function>ShellExecute</function>
|
|
to start other applications.</para>
|
|
|
|
<para>When a Cygwin application is started, the Windows idea of the current
|
|
working directory (CWD) is not necessarily the same as the Cygwin CWD.
|
|
There are a couple of restrictions in the Win32 API, which disallow certain
|
|
directories as Win32 CWD:</para>
|
|
|
|
<itemizedlist spacing="compact">
|
|
<listitem>
|
|
<para>The Windows subsystem only supports CWD paths of up to 258 chars.
|
|
This restriction doesn't apply for Cygwin processes, at least not as
|
|
long as they use the POSIX API (chdir, getcwd). This means, if a Cygwin
|
|
process has a CWD using an absolute path longer than 258 characters, the
|
|
Cygwin CWD and the Windows CWD differ.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>The Win32 API call to set the current directory,
|
|
<function>SetCurrentDirectory</function>, fails for directories for which
|
|
the user has no permissions, even if the user is an administrator. This
|
|
restriction doesn't apply for Cygwin processes, if they are running under
|
|
an administrator account.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><function>SetCurrentDirectory</function> does not support
|
|
case-sensitive filenames.
|
|
</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>Last, but not least, <function>SetCurrentDirectory</function> can't
|
|
work on virtual Cygwin paths like /proc or /cygdrive. These paths only
|
|
exists in the Cygwin realm so they have no meaning to a native Win32
|
|
process.</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
|
|
<para>As long as the Cygwin CWD is usable as Windows CWD, the Cygwin and
|
|
Windows CWDs are in sync within a process. However, if the Cygwin process
|
|
changes its working directory into one of the directories which are
|
|
unusable as Windows CWD, we're in trouble. If the process uses the
|
|
Win32 API to access a file using a relative pathname, the resulting
|
|
absolute path would not match the expectations of the process. In the
|
|
worst case, the wrong files are deleted.</para>
|
|
|
|
<para>To workaround this problem, Cygwin sets the Windows CWD to a special
|
|
directory in this case. This special directory points to a virtual
|
|
filesystem within the native NT namespace (<filename>\??\PIPE\</filename>).
|
|
Since it's not a real filesystem, the deliberate effect is that a call to,
|
|
for instance, <function>CreateFile ("foo", ...);</function> will fail,
|
|
as long as the processes CWD doesn't work as Windows CWD.</para>
|
|
|
|
<para>So, in general, don't use the Win32 file API in Cygwin applications.
|
|
If you <emphasis role='bold'>really</emphasis> need to access files using
|
|
the Win32 API, or if you <emphasis role='bold'>really</emphasis> have to use
|
|
<function>CreateProcess</function> to start applications, rather than
|
|
the POSIX <function>exec(3)</function> family of functions, you have to
|
|
make sure that the Cygwin CWD is set to some directory which is valid as
|
|
Win32 CWD.</para>
|
|
|
|
</sect2>
|
|
|
|
<sect2 id="pathnames-additional"><title>Additional Path-related Information</title>
|
|
|
|
<para>The <command>cygpath</command> program provides the ability to
|
|
translate between Win32 and POSIX pathnames in shell scripts. See
|
|
<xref linkend="cygpath"></xref> for the details.</para>
|
|
|
|
<para>The <envar>HOME</envar>, <envar>PATH</envar>, and
|
|
<envar>LD_LIBRARY_PATH</envar> environment variables are automatically
|
|
converted from Win32 format to POSIX format (e.g. from
|
|
<filename>c:/cygwin\bin</filename> to <filename>/bin</filename>, if
|
|
there was a mount from that Win32 path to that POSIX path) when a Cygwin
|
|
process first starts.</para>
|
|
|
|
<para>Symbolic links can also be used to map Win32 pathnames to POSIX.
|
|
For example, the command
|
|
<command>ln -s //pollux/home/joe/data /data</command> would have about
|
|
the same effect as creating a mount point from
|
|
<filename>//pollux/home/joe/data</filename> to <filename>/data</filename>
|
|
using <command>mount</command>, except that symbolic links cannot set
|
|
the default file access mode. Other differences are that the mapping is
|
|
distributed throughout the file system and proceeds by iteratively
|
|
walking the directory tree instead of matching the longest prefix in a
|
|
kernel table. Note that symbolic links will only work on network
|
|
drives that are properly configured to support the "system" file
|
|
attribute. Many do not do so by default (the Unix Samba server does
|
|
not by default, for example).</para>
|
|
|
|
</sect2>
|
|
|
|
</sect1>
|