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diff --git a/winsup/doc/pathnames.sgml b/winsup/doc/pathnames.sgml deleted file mode 100644 index e282cfb35..000000000 --- a/winsup/doc/pathnames.sgml +++ /dev/null @@ -1,975 +0,0 @@ -<sect1 id="using-pathnames"><title>Mapping path names</title> - -<sect2 id="pathnames-intro"><title>Introduction</title> - -<para>Cygwin supports both Win32- and POSIX-style paths. Directory -delimiters may be either forward slashes or backslashes. Paths using -backslashes 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. UNC pathnames -(starting with two slashes and a network name) are also supported.</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 existance 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 -stored in the <filename>/etc/passwd</filename> file. 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. The notable exception is the file system type -cygdrive. This type is used to set the cygdrive prefix.</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) 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). - 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 without ACL support:</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 invoking 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="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 <literal>/cygdrive</literal>, 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 <literal>/cygdrive/x/file</literal> 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-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 caseinsensitive, 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 casesensitivity 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> - -<sect1 id="using-specialnames"><title>Special filenames</title> - -<sect2 id="pathnames-etc"><title>Special files in /etc</title> - -<para>Certain files in Cygwin's <filename>/etc</filename> directory are -read by Cygwin before the mount table has been established. The list -of files is</para> - -<screen> - /etc/fstab - /etc/fstab.d/$USER - /etc/passwd - /etc/group -</screen> - -<para>These file are read using native Windows NT functions which have -no notion of Cygwin symlinks or POSIX paths. For that reason -there are a few requirements as far as <filename>/etc</filename> is -concerned.</para> - -<para>To access these files, the Cygwin DLL evaluates it's own full -Windows path, strips off the innermost directory component and adds -"\etc". Let's assume the Cygwin DLL is installed as -<filename>C:\cygwin\bin\cygwin1.dll</filename>. First the DLL name as -well as the innermost directory (<filename>bin</filename>) is stripped -off: <filename>C:\cygwin\</filename>. Then "etc" and the filename to -look for is attached: <filename>C:\cygwin\etc\fstab</filename>. So the -/etc directory must be parallel to the directory in which the cygwin1.dll -exists and <filename>/etc</filename> must not be a Cygwin symlink -pointing to another directory. Consequentially none of the files from -the above list, including the directory <filename>/etc/fstab.d</filename> -is allowed to be a Cygwin symlink either.</para> - -<para>However, native NTFS symlinks and reparse points are transparent -when accessing the above files so all these files as well as -<filename>/etc</filename> itself may be NTFS symlinks or reparse -points.</para> - -<para>Last but not least, make sure that these files are world-readable. -Every process of any user account has to read these files potentially, -so world-readability is essential. The only exception are the user -specific files <filename>/etc/fstab.d/$USER</filename>, which only have -to be readable by the $USER user account itself.</para> - -</sect2> - -<sect2 id="pathnames-dosdevices"><title>Invalid filenames</title> - -<para>Filenames invalid under Win32 are not necessarily invalid -under Cygwin since release 1.7.0. There are a few rules which -apply to Windows filenames. Most notably, DOS device names like -<filename>AUX</filename>, <filename>COM1</filename>, -<filename>LPT1</filename> or <filename>PRN</filename> (to name a few) -cannot be used as filename or extension in a native Win32 application. -So filenames like <filename>prn.txt</filename> or <filename>foo.aux</filename> -are invalid filenames for native Win32 applications.</para> - -<para>This restriction doesn't apply to Cygwin applications. Cygwin -can create and access files with such names just fine. Just don't try -to use these files with native Win32 applications.</para> - -</sect2> - -<sect2 id="pathnames-specialchars"> -<title>Forbidden characters in filenames</title> - -<para>Some characters are disallowed in filenames on Windows filesystems. -These forbidden characters are the ASCII control characters from ASCII -value 1 to 31, plus the following characters which have a special meaning -in the Win32 API:</para> - -<screen> - " * : < > ? | \ -</screen> - -<para>Cygwin can't fix this, but it has a method to workaround this -restriction. All of the above characters, except for the backslash, -are converted to special UNICODE characters in the range 0xf000 to 0xf0ff -(the "Private use area") when creating or accessing files.</para> - -<para>The backslash has to be exempt from this conversion, because Cygwin -accepts Win32 filenames including backslashes as path separators on input. -Converting backslashes using the above method would make this impossible.</para> - -<para>Additionally Win32 filenames can't contain trailing dots and spaces -for DOS backward compatibility. When trying to create files with trailing -dots or spaces, all of them are removed before the file is created. This -restriction only affects native Win32 applications. Cygwin applications -can create and access files with trailing dots and spaces without problems. -</para> - -<para>An exception from this rule are some network filesystems (NetApp, -NWFS) which choke on these filenames. They return with an error like -"No such file or directory" when trying to create such files. Starting -with Cygwin 1.7.6, Cygwin recognizes these filesystems and works around -this problem by applying the same rule as for the other forbidden characters. -Leading spaces and trailing dots and spaces will be converted to UNICODE -characters in the private use area. This behaviour can be switched on -explicitely for a filesystem or a directory tree by using the mount option -<literal>dos</literal>.</para> - -</sect2> - -<sect2 id="pathnames-unusual"> -<title>Filenames with unusual (foreign) characters</title> - -<para> Windows filesystems use Unicode encoded as UTF-16 -to store filename information. If you don't use the UTF-8 -character set (see <xref linkend="setup-locale"></xref>) then there's a -chance that a filename is using one or more characters which have no -representation in the character set you're using.</para> - -<note><para>In the default "C" locale, Cygwin creates filenames using -the UTF-8 charset. This will always result in some valid filename by -default, but again might impose problems when switching to a non-"C" -or non-"UTF-8" charset.</para></note> - -<note><para>To avoid this scenario altogether, always use UTF-8 as the -character set.</para></note> - -<para>If you don't want or can't use UTF-8 as character set for whatever -reason, you will nevertheless be able to access the file. How does that -work? When Cygwin converts the filename from UTF-16 to your character -set, it recognizes characters which can't be converted. If that occurs, -Cygwin replaces the non-convertible character with a special character -sequence. The sequence starts with an ASCII CAN character (hex code -0x18, equivalent Control-X), followed by the UTF-8 representation of the -character. The result is a filename containing some ugly looking -characters. While it doesn't <emphasis role='bold'>look</emphasis> nice, it -<emphasis role='bold'>is</emphasis> nice, because Cygwin knows how to convert -this filename back to UTF-16. The filename will be converted using your -usual character set. However, when Cygwin recognizes an ASCII CAN -character, it skips over the ASCII CAN and handles the following bytes as -a UTF-8 character. Thus, the filename is symmetrically converted back to -UTF-16 and you can access the file.</para> - -<note><para>Please be aware that this method is not entirely foolproof. -In some character set combinations it might not work for certain native -characters.</para> - -<para>Only by using the UTF-8 charset you can avoid this problem safely. -</para></note> - -</sect2> - -<sect2 id="pathnames-casesensitive"> -<title>Case sensitive filenames</title> - -<para>In the Win32 subsystem filenames are only case-preserved, but not -case-sensitive. You can't access two files in the same directory which -only differ by case, like <filename>Abc</filename> and -<filename>aBc</filename>. While NTFS (and some remote filesystems) -support case-sensitivity, the NT kernel starting with Windows XP does -not support it by default. Rather, you have to tweak a registry setting -and reboot. For that reason, case-sensitivity can not be supported by Cygwin, -unless you change that registry value.</para> - -<para>If you really want case-sensitivity in Cygwin, you can switch it -on by setting the registry value</para> - -<screen> -HKLM\SYSTEM\CurrentControlSet\Control\Session Manager\kernel\obcaseinsensitive -</screen> - -<para>to 0 and reboot the machine. For least surprise, Cygwin expects -this registry value also on Windows NT4 and Windows 2000, which usually -both don't know this registry key. If you want case-sensitivity on these -systems, create that registry value and set it to 0. On these systems -(and <emphasis role='bold'>only</emphasis> on these systems) you don't have to reboot to bring it -into effect, rather stopping all Cygwin processes and then restarting them -is sufficient.</para> - -<note> -<para> -When installing Microsoft's Services For Unix (SFU), you're asked if -you want to use case-sensitive filenames. If you answer "yes" at this point, -the installer will change the aforementioned registry value to 0, too. So, if -you have SFU installed, there's some chance that the registry value is already -set to case sensitivity. -</para> -</note> - -<para>After you set this registry value to 0, Cygwin will be case-sensitive -by default on NTFS and NFS filesystems. However, there are limitations: -while two <emphasis role='bold'>programs</emphasis> <filename>Abc.exe</filename> -and <filename>aBc.exe</filename> can be created and accessed like other files, -starting applications is still case-insensitive due to Windows limitations -and so the program you try to launch may not be the one actually started. Also, -be aware that using two filenames which only differ by case might -result in some weird interoperability issues with native Win32 applications. -You're using case-sensitivity at your own risk. You have been warned! </para> - -<para>Even if you use case-sensitivity, it might be feasible to switch to -case-insensitivity for certain paths for better interoperability with -native Win32 applications (even if it's just Windows Explorer). You can do -this on a per-mount point base, by using the "posix=0" mount option in -<filename>/etc/fstab</filename>, or your <filename>/etc/fstab.d/$USER</filename> -file.</para> - -<para><filename>/cygdrive</filename> paths are case-insensitive by default. -The reason is that the native Windows %PATH% environment variable is not -always using the correct case for all paths in it. As a result, if you use -case-sensitivity on the <filename>/cygdrive</filename> prefix, your shell -might claim that it can't find Windows commands like <command>attrib</command> -or <command>net</command>. To ease the pain, the <filename>/cygdrive</filename> -path is case-insensitive by default and you have to use the "posix=1" setting -explicitly in <filename>/etc/fstab</filename> or -<filename>/etc/fstab.d/$USER</filename> to switch it to case-sensitivity, -or you have to make sure that the native Win32 %PATH% environment variable -is using the correct case for all paths throughout.</para> - -<para>Note that mount points as well as device names and virtual -paths like /proc are always case-sensitive! The only exception are -the subdirectories and filenames under /proc/registry, /proc/registry32 -and /proc/registry64. Registry access is always case-insensitive. -Read on for more information.</para> - -</sect2> - -<sect2 id="pathnames-posixdevices"> <title>POSIX devices</title> -<para>There is no need to create a POSIX <filename>/dev</filename> -directory as Cygwin automatically simulates it internally. -These devices cannot be seen with the command <command>ls /dev/</command> -although commands such as <command>ls /dev/tty</command> work fine. -If you want to be able to see all well-known devices in -<filename>/dev/</filename>, you can use Igor Pechtchanski's -<ulink -url="http://cygwin.com/ml/cygwin/2004-03/txt00028.txt">create_devices.sh</ulink> -script. This script does not add the raw disk devices, though. Again, -it's not necessary to see an existing device in /dev to access it. The script -is just for the fun of it. -</para> - -<para> -Cygwin supports the following character devices commonly found on POSIX systems: -</para> - -<screen> -/dev/null -/dev/zero -/dev/full - -/dev/console Pseudo device name for the standard console window created - by Windows. Same as the one used for cmd.exe. Every one - of them has this name. It's not quite comparable with the - console device on UNIX machines. - -/dev/tty The current tty of a session running in a pseudo tty. -/dev/ptmx Pseudo tty master device. -/dev/ttym - -/dev/tty0 Pseudo ttys are numbered from /dev/tty0 upwards as they are -/dev/tty1 requested. -... - -/dev/ttyS0 Serial communication devices. ttyS0 == Win32 COM1, -/dev/ttyS1 ttyS1 == COM2, etc. -... - -/dev/pipe -/dev/fifo - -/dev/mem The physical memory of the machine. Note that access to the -/dev/port physical memory has been restricted with Windows Server 2003. -/dev/kmem Since this OS, you can't access physical memory from user space. - -/dev/kmsg Kernel message pipe, for usage with sys logger services. - -/dev/random Random number generator. -/dev/urandom - -/dev/dsp Default sound device of the system. -</screen> - -<para> -Cygwin also has several Windows-specific devices: -</para> - -<screen> -/dev/com1 The serial ports, starting with COM1 which is the same as ttyS0. -/dev/com2 Please use /dev/ttySx instead. -... - -/dev/conin Same as Windows CONIN$. -/dev/conout Same as Windows CONOUT$. -/dev/clipboard The Windows clipboard, text only -/dev/windows The Windows message queue. -</screen> - -<para> -Block devices are accessible by Cygwin processes using fixed POSIX device -names. These POSIX device names are generated using a direct conversion -from the POSIX namespace to the internal NT namespace. -E.g. the first harddisk is the NT internal device \device\harddisk0\partition0 -or the first partition on the third harddisk is \device\harddisk2\partition1. -The first floppy in the system is \device\floppy0, the first CD-ROM is -\device\cdrom0 and the first tape drive is \device\tape0.</para> - -<para>The mapping from physical device to the name of the device in the -internal NT namespace can be found in various places. For hard disks and -CD/DVD drives, the Windows "Disk Management" utility (part of the -"Computer Management" console) shows that the mapping of "Disk 0" is -\device\harddisk0. "CD-ROM 2" is \device\cdrom2. Another place to find -this mapping is the "Device Management" console. Disks have a -"Location" number, tapes have a "Tape Symbolic Name", etc. -Unfortunately, the places where this information is found is not very -well-defined.</para> - -<para> -For external disks (USB-drives, CF-cards in a cardreader, etc) you can use -Cygwin to show the mapping. <filename>/proc/partitions</filename> -contains a list of raw drives known to Cygwin. The <command>df</command> -command shows a list of drives and their respective sizes. If you match -the information between <filename>/proc/partitions</filename> and the -<command>df</command> output, you should be able to figure out which -external drive corresponds to which raw disk device name.</para> - -<note><para>Apart from tape devices which are not block devices and are -by default accessed directly, accessing mass storage devices raw -is something you should only do if you know what you're doing and know how to -handle the information. <emphasis role='bold'>Writing</emphasis> to a raw -mass storage device you should only do if you -<emphasis role='bold'>really</emphasis> know what you're doing and are aware -of the fact that any mistake can destroy important information, for the -device, and for you. So, please, handle this ability with care. -<emphasis role='bold'>You have been warned.</emphasis></para></note> - -<para> -Last but not least, the mapping from POSIX /dev namespace to internal -NT namespace is as follows: -</para> - -<screen> -POSIX device name Internal NT device name - -/dev/st0 \device\tape0, rewind -/dev/nst0 \device\tape0, no-rewind -/dev/st1 \device\tape1 -/dev/nst1 \device\tape1 -... -/dev/st15 -/dev/nst15 - -/dev/fd0 \device\floppy0 -/dev/fd1 \device\floppy1 -... -/dev/fd15 - -/dev/sr0 \device\cdrom0 -/dev/sr1 \device\cdrom1 -... -/dev/sr15 - -/dev/scd0 \device\cdrom0 -/dev/scd1 \device\cdrom1 -... -/dev/scd15 - -/dev/sda \device\harddisk0\partition0 (whole disk) -/dev/sda1 \device\harddisk0\partition1 (first partition) -... -/dev/sda15 \device\harddisk0\partition15 (fifteenth partition) - -/dev/sdb \device\harddisk1\partition0 -/dev/sdb1 \device\harddisk1\partition1 - -[up to] - -/dev/sddx \device\harddisk127\partition0 -/dev/sddx1 \device\harddisk127\partition1 -... -/dev/sddx15 \device\harddisk127\partition15 -</screen> - -<para> -if you don't like these device names, feel free to create symbolic -links as they are created on Linux systems for convenience: -</para> - -<screen> -ln -s /dev/sr0 /dev/cdrom -ln -s /dev/nst0 /dev/tape -... -</screen> - -</sect2> - -<sect2 id="pathnames-exe"><title>The .exe extension</title> - -<para>Win32 executable filenames end with <filename>.exe</filename> -but the <filename>.exe</filename> need not be included in the command, -so that traditional UNIX names can be used. However, for programs that -end in <filename>.bat</filename> and <filename>.com</filename>, you -cannot omit the extension. </para> - -<para>As a side effect, the <command> ls filename</command> gives -information about <filename>filename.exe</filename> if -<filename>filename.exe</filename> exists and <filename>filename</filename> -does not. In the same situation the function call -<function>stat("filename",..)</function> gives information about -<filename>filename.exe</filename>. The two files can be distinguished -by examining their inodes, as demonstrated below. -<screen> -<prompt>bash$</prompt> <userinput>ls * </userinput> -a a.exe b.exe -<prompt>bash$</prompt> <userinput>ls -i a a.exe</userinput> -445885548 a 435996602 a.exe -<prompt>bash$</prompt> <userinput>ls -i b b.exe</userinput> -432961010 b 432961010 b.exe -</screen> -If a shell script <filename>myprog</filename> and a program -<filename>myprog.exe</filename> coexist in a directory, the shell -script has precedence and is selected for execution of -<command>myprog</command>. Note that this was quite the reverse up to -Cygwin 1.5.19. It has been changed for consistency with the rest of Cygwin. -</para> - -<para>The <command>gcc</command> compiler produces an executable named -<filename>filename.exe</filename> when asked to produce -<filename>filename</filename>. This allows many makefiles written -for UNIX systems to work well under Cygwin.</para> - -</sect2> - -<sect2 id="pathnames-proc"><title>The /proc filesystem</title> -<para> -Cygwin, like Linux and other similar operating systems, supports the -<filename>/proc</filename> virtual filesystem. The files in this -directory are representations of various aspects of your system, -for example the command <userinput>cat /proc/cpuinfo</userinput> -displays information such as what model and speed processor you have. -</para> -<para> -One unique aspect of the Cygwin <filename>/proc</filename> filesystem -is <filename>/proc/registry</filename>, see next section. -</para> -<para> -The Cygwin <filename>/proc</filename> is not as complete as the -one in Linux, but it provides significant capabilities. The -<systemitem>procps</systemitem> package contains several utilities -that use it. -</para> -</sect2> - -<sect2 id="pathnames-proc-registry"><title>The /proc/registry filesystem</title> -<para> -The <filename>/proc/registry</filename> filesystem provides read-only -access to the Windows registry. It displays each <literal>KEY</literal> -as a directory and each <literal>VALUE</literal> as a file. As anytime -you deal with the Windows registry, use caution since changes may result -in an unstable or broken system. There are additionally subdirectories called -<filename>/proc/registry32</filename> and <filename>/proc/registry64</filename>. -They are identical to <filename>/proc/registry</filename> on 32 bit -host OSes. On 64 bit host OSes, <filename>/proc/registry32</filename> -opens the 32 bit processes view on the registry, while -<filename>/proc/registry64</filename> opens the 64 bit processes view. -</para> -<para> -Reserved characters ('/', '\', ':', and '%') or reserved names -(<filename>.</filename> and <filename>..</filename>) are converted by -percent-encoding: -<screen> -<prompt>bash$</prompt> <userinput>regtool list -v '\HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices'</userinput> -... -\DosDevices\C: (REG_BINARY) = cf a8 97 e8 00 08 fe f7 -... -<prompt>bash$</prompt> <userinput>cd /proc/registry/HKEY_LOCAL_MACHINE/SYSTEM</userinput> -<prompt>bash$</prompt> <userinput>ls -l MountedDevices</userinput> -... --r--r----- 1 Admin SYSTEM 12 Dec 10 11:20 %5CDosDevices%5CC%3A -... -<prompt>bash$</prompt> <userinput>od -t x1 MountedDevices/%5CDosDevices%5CC%3A</userinput> -0000000 cf a8 97 e8 00 08 fe f7 01 00 00 00 -</screen> -The unnamed (default) value of a key can be accessed using the filename -<filename>@</filename>. -</para> -<para> -If a registry key contains a subkey and a value with the same name -<filename>foo</filename>, Cygwin displays the subkey as -<filename>foo</filename> and the value as <filename>foo%val</filename>. -</para> -</sect2> - -<sect2 id="pathnames-at"><title>The @pathnames</title> -<para>To circumvent the limitations on shell line length in the native -Windows command shells, Cygwin programs expand their arguments -starting with "@" in a special way. If a file -<filename>pathname</filename> exists, the argument -<filename>@pathname</filename> expands recursively to the content of -<filename>pathname</filename>. Double quotes can be used inside the -file to delimit strings containing blank space. -Embedded double quotes must be repeated. -In the following example compare the behaviors of the bash built-in -<command>echo</command> and of the program <command>/bin/echo</command>.</para> - -<example id="pathnames-at-ex"><title> Using @pathname</title> -<screen> -<prompt>bash$</prompt> <userinput>echo 'This is "a long" line' > mylist</userinput> -<prompt>bash$</prompt> <userinput>echo @mylist</userinput> -@mylist -<prompt>bash$</prompt> <userinput>cmd</userinput> -<prompt>c:\></prompt> <userinput>c:\cygwin\bin\echo @mylist</userinput> -This is a long line -</screen> -</example> -</sect2> -</sect1> |