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* cygwinenv.xml (cygwinenv-implemented-options): Explain new
winsymliks:nativestrict option. Strip out description of symlink types and refer to new pathnames-symlinks section. * highlights.xml (ov-hi-files): Rip out most of symlink description and refer to new pathnames-symlinks section instead. * new-features.xml (ov-new1.7.19): Add CYGWIN=winsymlinks:nativestrict. * pathnames.xml (pathnames-symlinks): New section describing symbolic link handling.
This commit is contained in:
Corinna Vinschen
parent
33cb946e7e
commit
6d383d0fde
@ -1,12 +1,23 @@
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2013-05-23 Corinna Vinschen <corinna@vinschen.de>
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* cygwinenv.xml (cygwinenv-implemented-options): Explain new
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winsymliks:nativestrict option. Strip out description of symlink types
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and refer to new pathnames-symlinks section.
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* highlights.xml (ov-hi-files): Rip out most of symlink description and
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refer to new pathnames-symlinks section instead.
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* new-features.xml (ov-new1.7.19): Add CYGWIN=winsymlinks:nativestrict.
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* pathnames.xml (pathnames-symlinks): New section describing symbolic
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link handling.
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2013-05-21 Corinna Vinschen <corinna@vinschen.de>
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* new-features.sgml (ov-new1.7.19): Add arc4random,
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* new-features.xml (ov-new1.7.19): Add arc4random,
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arc4random_addrandom, arc4random_buf, arc4random_stir and
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arc4random_uniform.
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2013-05-21 Corinna Vinschen <corinna@vinschen.de>
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* new-features.sgml (ov-new1.7.19): Add __b64_ntop and __b64_pton.
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* new-features.xml (ov-new1.7.19): Add __b64_ntop and __b64_pton.
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2013-05-13 Warren Young <warren@etr-usa.com>
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@ -82,26 +82,27 @@ time and when handles are inherited. Defaults to set.</para>
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</listitem>
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<listitem>
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<para><envar>winsymlinks:{lnk,native}</envar> - if set to just
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<para><envar>winsymlinks:{lnk,native,nativestrict}</envar> - if set to just
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<literal>winsymlinks</literal> or <literal>winsymlinks:lnk</literal>,
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Cygwin creates symlinks as Windows shortcuts with a special header and
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the R/O attribute set. If set to <literal>winsymlinks:native</literal>,
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Cygwin creates symlinks as native Windows symlinks as supported by NTFS
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since Windows Vista/2008.
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the R/O attribute set.</para>
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If not set, Cygwin creates symlinks as plain files with a magic number,
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a path and the DOS SYSTEM attribute set by default, unless this is not
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supported by the underlying filesystem. For instance, on MVFS symlinks
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are always created as Windows shortcuts, because it doesn't support the
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DOS SYSTEM attribute, on AFS always as native symlink because it doesn't
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support DOS attributes. On NFS, symlinks are always created as native
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symlinks of the underlying filesystem.
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</para>
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<para>If set to <literal>winsymlinks:native</literal> or
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<literal>winsymlinks:nativestrict</literal>, Cygwin creates symlinks as
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native Windows symlinks on filesystems and OS versions supporting them.
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If the OS is known not to support native symlinks (Windows XP, Windows
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Server 2003), a warning message is produced once per session.</para>
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<para>Please note that symlinks created under Cygwin 1.7 or later are
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not readable by older Cygwin releases because the new symlinks use UTF-16
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to encode the target filename, while the old symlinks used the current
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ANSI or OEM charset.</para>
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<para>The difference between <literal>winsymlinks:native</literal> and
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<literal>winsymlinks:nativestrict</literal> is this: If the filesystem
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supports native symlinks and Cygwin fails to create a native symlink for
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some reason, it will fall back to creating Cygwin default symlinks
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with <literal>winsymlinks:native</literal>, while with
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<literal>winsymlinks:nativestrict</literal> the <literal>symlink(2)</literal>
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system call will immediately fail.</para>
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<para>For more information on symbolic links, see
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<xref linkend="pathnames-symlinks"></xref>.</para>
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</listitem>
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</itemizedlist>
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@ -113,30 +113,9 @@ supporting that. Since Windows XP, the OS only supports case
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sensitivity when a specific registry value is changed. Therefore, case
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sensitivity is not usually the default.</para>
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<para>Symbolic links are not present and supported on Windows up to and
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including Windows Server 2003 R2. Native symlinks are available starting
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with Windows Vista. Due to their strange implementation, however,
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they are not useful in a POSIX emulation layer. Cygwin recognizes
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native symlinks, but does not create them.</para>
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<para>Symbolic links are potentially created in two different ways.
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The file style symlinks are files containing a magic cookie followed by
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the path to which the link points. They are marked with the System DOS
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attribute so that only files with that attribute have to be read to
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determine whether or not the file is a symbolic link. The shortcut style
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symlinks are Windows shortcut files with a special header and the
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Readonly DOS attribute set. The advantage of file symlinks is speed,
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the advantage of shortcut symlinks is the fact that they can be utilized
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by non-Cygwin Win32 tools as well.</para>
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<para>Starting with Cygwin 1.7, symbolic links are using UTF-16 to encode
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the filename of the target file, to better support internationalization.
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Symlinks created by older Cygwin releases can be read just fine. However,
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you could run into problems with them if you're now using another character
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set than the one you used when creating these symlinks
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(see <xref linkend="setup-locale-problems"></xref>. Please note that this
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new UTF-16 style of symlinks is not compatible with older Cygwin release,
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which can't read the target filename correctly.</para>
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<para>Cygwin supports creating and reading symbolic links, even on Windows
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filesystems and OS versions which don't support them.
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See <xref linkend="pathnames-symlinks"></xref> for details.</para>
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<para>Hard links are fully supported on NTFS and NFS file systems. On FAT
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and other file systems which don't support hardlinks, the call returns with
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@ -18,7 +18,8 @@ Add support for building a 64 bit version of Cygwin on x86_64 natively.
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<listitem><para>
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Add support for creating native NTFS symlinks starting with Windows Vista
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by setting the CYGWIN=winsymlinks:native option.
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by setting the CYGWIN=winsymlinks:native or CYGWIN=winsymlinks:nativestrict
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option.
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</para></listitem>
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<listitem><para>
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@ -355,6 +355,81 @@ the cygdrive prefix, use a distinct path prefix:</para>
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</sect2>
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<sect2 id="pathnames-symlinks"><title>Symbolic links</title>
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<para>Symbolic links are not present and supported on Windows until Windows
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Vista/Server 2008, and then only on some filesystems. Since POSIX applications
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are rightfully expecting to use symlinks and the
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<literal>symlink(2)</literal> system call, Cygwin had to find a
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workaround for this Windows flaw.</para>
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<para>Cygwin creates symbolic links potentially in multiple different
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ways:</para>
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<itemizedlist mark="bullet">
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<listitem>
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<para>The default symlinks are plain files containing a magic cookie
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followed by the path to which the link points. They are marked with the
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DOS SYSTEM attribute so that only files with that attribute have to be
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read to determine whether or not the file is a symbolic link.</para>
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<note><para>Starting with Cygwin 1.7, symbolic links are using UTF-16 to encode
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the filename of the target file, to better support internationalization.
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Symlinks created by older Cygwin releases can be read just fine. However,
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you could run into problems with them if you're now using another character
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set than the one you used when creating these symlinks
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(see <xref linkend="setup-locale-problems"></xref>). Please note that this
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new UTF-16 style of symlinks is not compatible with older Cygwin release,
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which can't read the target filename correctly.</para></note>
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</listitem>
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<listitem>
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<para>The shortcut style symlinks are Windows <literal>.lnk</literal>
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shortcut files with a special header and the DOS READONLY attribute set.
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This symlink type is created if the environment variable
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<literal>CYGWIN</literal> (see <xref linkend="using-cygwinenv"></xref>)
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is set to contain the string <literal>winsymlinks</literal> or
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<literal>winsymlinks:lnk</literal>. On the MVFS filesystem, which does
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not support the DOS SYSTEM attribute, this is the one and only supported
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symlink type, independently from the <literal>winsymlinks</literal>
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setting.</para>
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</listitem>
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<listitem>
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<para>Native Windows symlinks are only created on Windows Vista/2008 and later,
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and only on filesystems supporting reparse points. Due to to their weird
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restrictions and behaviour, they are only created if the user
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explicitely requests creating them. This is done by setting the
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environment variable <literal>CYGWIN</literal> to contain the string
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<literal>winsymlinks:native</literal> or
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<literal>winsymlinks:nativestrict</literal>. For the difference between
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these two settings, see <xref linkend="using-cygwinenv"></xref>.
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On AFS, native symlinks are the only supported type of symlink due to
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AFS lacking support for DOS attributes. This is independent from the
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<literal>winsymlinks</literal> setting.</para>
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</listitem>
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<listitem>
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<para>On the NFS filesystem, Cygwin always creates real NFS symlinks.</para>
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</listitem>
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</itemizedlist>
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<para>All of the above four symlink types are recognized and used as symlinks
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under all circumstances. However, if the default plain file symlink type
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is lacking its DOS SYSTEM bit, or if the shortcut file is lacking the DOS
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READONLY attribute, they are not recognized as symlink.</para>
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<para>Apart from these four types, there's also a fifth type, which is
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recognized as symlink but never generated by Cygwin, directory
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junctions. This is an older reparse point type, supported by Windows
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since Windows 2000. Filesystem junctions on the other hand are not
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handled as symlinks, since otherwise they would not be recognized as
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filesystem borders by commands like <command>find -xdev</command>.</para>
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</sect2>
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<sect2 id="pathnames-win32"><title>Using native Win32 paths</title>
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<para>Using native Win32 paths in Cygwin, while possible, is generally
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