OS X extended attributes
Like most other modern filesystems the HFS filesystem on OS X supports extended attributes and OS X access control lists ACL,
Files on OS X using the systems standard HFS file system consists of parts:
- Payload data
-
The actual data
- Extended Attributes
-
like icons
- Finder meta-file
-
color tags, description
The OX on board Unix commands like cp copy the OS X extended attributes when the target system supports it.
For user uses like the tar archiver Apple has developed a format to store the extended attributes in a separate file.
AppleSingle' combined both file forks and the related Finder meta-file information into a single file, whereas 'AppleDouble stored them as two separate files.
To list extended attributes from the command line specify the @-switch with the Unix Unix-ls command:
ls -l@ *
-rw-r--r--@ 1 ckent staff 225868823 Sep 9 2012 Myfile01.flv
com.apple.FinderInfo 42
com.apple.ResourceFork 41338
The xattr command displays and manipulates extended attributes on OS X.
xattr -l MyMovie.flv
com.apple.FinderInfo:
00000000 00 00 00 00 00 00 00 00 04 08 00 00 00 00 00 00 |................|
com.apple.ResourceFork:
00000010 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
The Unix-tar archiver command stores OS X extended attributes in a separate file in AppleDouble format.
time ( tar cvf - . |( cd /Volumes/UserHDA/ahaack/; tar xvf - )) 2> /tmp/kenterr.log
Status: Published Date: 2017/06/05 14:13:06 Revision: 1.1
Copyright bei Andreas Haack (C) 2014.
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