Extended file attributes
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Extended file attributes is a filesystem feature that enables users to associate arbitrary metadata with computer files, whereas regular attributes have a strictly defined purpose (such as permissions or records of creation and modification times). Typical uses can be storing the author of a document, the character encoding of a plain-text document, or a checksum.
Linux extended attributes
On Linux, the ext2, ext3 and XFS filesystems support extended attributes if the feature is enabled in the kernel configuration. Any regular file may have a list of extended attributes. Each attribute is denoted by a name and the associated data. The name must be a null-terminated string, and must be prefixed by a namespace identifier and a dot character. Currently, three namespaces exist: user, trusted and system. The user namespace has no restrictions with regard to naming or contents. The system namespace is primarily used by the kernel for access control lists.The use of extended attributes on Linux is not widely deployed in user-space programs, although it is a part of the standard 2.6 linux kernel series.
OS/2
Parts of OS/2 like the Workplace Shell uses several standardized "Extended Attributes" (also EAs) for purposes like identifying the filetype, comments, computer icons and keywords about the file. Programs written in the interpreted language Rexx store an already interpreted version of the code as an extended attribute, to allow faster execution.The High Performance File System was written with attributes in mind, but support for it was also retro-fitted on the FAT filesystem of DOS. For compatibility with other operating systems using a FAT partition, the file system cluster corresponding to OS/2 attributes is assigned to a fictitious file.
See also
External links
- http://acl.bestbits.at/ - Linux Extended Attributes and ACLs
- [Implementation of OS/2 extended attributes on the FAT file system].
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