35 lines
1.9 KiB
Plaintext
35 lines
1.9 KiB
Plaintext
<sect1 id="using-filemodes"><title>File permissions</title>
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<para>On Windows 9x systems, files are always readable, and Cygwin uses the
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native read-only mode to determine if they are writable. Files are
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considered to be executable if the filename ends with .bat, .com or .exe, or
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if its content starts with #!. Consequently <command>chmod</command> can
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only affect the "w" mode, it silently ignores actions involving the other
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modes. This means that <command>ls -l</command>
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needs to open and read files. It can thus be relatively slow.</para>
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<para>Under NT, file permissions default to the same behavior as Windows
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9x but there is optional functionality in Cygwin that can make file
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systems behave more like on UNIX systems. This is turned on by adding
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the "ntea" option to the <EnVar>CYGWIN</EnVar> environment variable.</para>
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<para>When the "ntea" feature is activated, Cygwin will start with basic
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permissions as determined above, but can store POSIX file permissions in NT
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Extended Attributes. This feature works quite well on NTFS partitions
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because the attributes can be stored sensibly inside the normal NTFS
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filesystem structure. However, on a FAT partition, NT stores extended
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attributes in a flat file at the root of the partition called <filename>EA
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DATA. SF</filename>. This file can grow to extremely large sizes if you
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have a large number of files on the partition in question, slowing the
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system to a crawl. In addition, the <filename>EA DATA. SF</filename> file
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can only be deleted outside of Windows because of its "in use" status. For
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these reasons, the use of NT Extended Attributes is off by default in
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Cygwin. Finally, note that specifying "ntea" in <EnVar>CYGWIN</EnVar> has no
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effect under Windows 9x. </para>
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<para>Under NT, the test "[ -w filename]" is only true if filename is
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writable across the board, e.g. <command>chmod +w filename</command>. </para>
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</sect1>
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