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Extended file attributes is a file system feature that enables users to associate computer files with metadata not interpreted by the filesystem, whereas regular attributes have a purpose strictly defined by the filesystem (such as permissions or records of creation and modification times). Unlike forks, which can usually be as large as the maximum file size, extended attributes are usually limited in size to a value significantly smaller than the maximum file size. Typical uses can be storing the author of a document, the character encoding of a plain-text document, or a checksum. It has been suggested that Crash counting be merged into this article or section. ...
A computer file is a collection of information that is stored in a computer system and can be identified by its full path name. ...
The simplest definition of metadata is that it is data about data. ...
Most modern file systems have methods of administering permissions or access rights to specific users and groups of users. ...
In computer file systems, a fork is additional data associated with a file system object. ...
A character encoding or character set (sometimes referred to as code page) consists of a code that pairs a sequence of characters from a given set with something else, such as a sequence of natural numbers, octets or electrical pulses, in order to facilitate the storage of text in computers...
A cyclic redundancy check (CRC) is a type of hash function used to produce a checksum – a small, fixed number of bits – against a block of data, such as a packet of network traffic or a block of a computer file. ...
OS/2
In OS/2 version 1.2 and later, the High Performance File System was designed with extended attributes in mind, but support for them was also retro-fitted on the FAT filesystem of DOS. For compatibility with other operating systems using a FAT partition, OS/2 attributes are stored inside a single file "EA DATA. SF" located in the root directory. This file is normally inaccessible when an operating system supporting EAs manages the disk, but can be freely manipulated under for example DOS. Files and directories having extended attributes use one or more clusters inside this file. The logical cluster number of the first used cluster is stored inside the owning file's or directory's directory entry, in two previously unused bytes. These two bytes are used for other purposes on the FAT32 filesystem, and hence OS/2 extended attributes cannot be stored on this filesystem. To meet Wikipedias quality standards, this article or section may require cleanup. ...
HPFS or High Performance File System, is a file system created specifically for the OS/2 operating system to improve upon the limitations of the FAT file system. ...
File Allocation Table (FAT) is a partially patented file system developed by Microsoft for MS-DOS and was the primary file system for consumer versions of Microsoft Windows up to and including Windows Me. ...
In certain filesystem types like the File Allocation Table (FAT) filesystem of MS-DOS or the NTFS filesystem of Windows NT, a cluster is the unit of disk space allocation for files and directories. ...
Parts of OS/2 version 2.0 and later such as the Workplace Shell uses several standardized extended attributes (also called 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 parsed version of the code as an extended attribute, to allow faster execution. The OS/2 Warp 4 desktop (with some third-party enhancements installed as SOM classes) The Workplace Shell (WPS) is an award-winning object-oriented desktop shell produced by IBMs Boca Raton development lab for OS/2 2. ...
Mac OS X allows continuous scaling of icons up to 128x128 pixels A computer icon is a small pictogram, usually ranging from 16 by 16 pixels up to 128 by 128 pixels, which represents a file, folder, application or device on a computer operating system. ...
REXX (REstructured eXtended eXecutor) is an interpreted programming language which was developed at IBM. It is a structured high-level programming language which was designed to be both easy to learn and easy to read. ...
In grammar and linguistics, parsing is the process by which a person makes sense of a sentence, usually by breaking it down into words or phrases. ...
Windows NT Windows NT supports EAs on FAT and HPFS filesystems in the same way as OS/2 does. The NTFS file system was also designed to store them, as one of the many possible file forks, to accommodate the OS/2 subsystem. OS/2 extended attributes are accessible to any OS/2 programs the same way as in native OS/2 and to any Windows program through the BackupRead and BackupWrite system calls. They are notably used by the NFS server of the Interix POSIX subsystem in order to implement Unix-like permissions. Windows NT is a family of operating systems produced by Microsoft, the first version of which was released in July 1993. ...
To meet Wikipedias quality standards, this article or section may require cleanup. ...
NTFS is the standard file system of Windows NT, including its later versions Windows 2000, Windows XP, Windows Server 2003, and Windows Vista. ...
Network File System (NFS) is a network file system protocol originally developed by Sun Microsystems in 1984, allowing a user on a client computer to access files over a network as easily as if the network devices were attached to its local disks. ...
Interix is the name of an optional, full-featured POSIX and Unix environment subsystem for Microsofts Windows NT-based operating systems. ...
Linux In Linux, the ext2, ext3, ReiserFS and XFS filesystems support extended attributes (abbreviated xattr) if the libattr 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, four namespaces exist: user, trusted, security 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 security namespace is used by SELinux, for example. Linux (IPA pronunciation: ) is a Unix-like computer operating system. ...
The ext2 or second extended file system is a file system for the Linux kernel. ...
The ext3 or third extended filesystem is a journalled file system that is commonly used by the Linux operating system. ...
ReiserFS is a general-purpose, journaled computer file system designed and implemented by a team at Namesys led by Hans Reiser who is referred to as the projects Benevolent Dictator for Life. ...
XFS is a high-performance journaling file system created by Silicon Graphics for their IRIX operating system. ...
In various branches of mathematics and computer science, strings are sequences of various simple objects (symbols, tokens, characters, etc. ...
A namespace is a context in which a group of one or more identifiers might exist. ...
In computer security, an access control list (ACL) is a list of permissions attached to an object. ...
Security-Enhanced Linux (SELinux) is a version of the Linux kernel and utilities, which contains support for mandatory access controls based on the principle of least privilege. ...
Extended attributes are not widely used in user-space programs in Linux, although they are supported in the 2.6 and later versions of the kernel. The Beagle search tool, however, does use extended attributes, and freedesktop.org publishes recommendations for their use. The Linux kernel is a Unix-like operating system kernel. ...
Old UI for Beagle, code named Best Beagle is a search tool for Linux, enabling the user to search documents, chat logs, email and contact lists in a similar way to Spotlight in Mac OS X, or Google Desktop under Microsoft Windows. ...
freedesktop. ...
FreeBSD In FreeBSD 5.0 and later, the UFS1 and UFS2 filesystems support extended attributes. 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 exists in a namespace identified by a small-integer namespace identifier. Currently, two namespaces exist: user 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. FreeBSD is a Unix-like free operating system descended from AT&T UNIX via the Berkeley Software Distribution (BSD) branch through the 386BSD and 4. ...
The UNIX file system (UFS) is a file system used by many Unix and Unix-like operating systems. ...
In various branches of mathematics and computer science, strings are sequences of various simple objects (symbols, tokens, characters, etc. ...
In computer security, an access control list (ACL) is a list of permissions attached to an object. ...
Extended attributes are not widely used in user-space programs in FreeBSD.
Solaris The Solaris operating system version 9 and later allows files to have "extended attributes", which are effectively forks. Internally, they are actually stored and accessed like normal files, so their names cannot contain "/" characters, their size is practically unlimited and their ownership and permissions can differ from those of the parent file. Solaris is a computer operating system developed by Sun Microsystems. ...
Version 4 of the Network File System supports extended attributes in much the same way as Solaris. Network File System (NFS) is a network file system protocol originally developed by Sun Microsystems in 1984, allowing a user on a client computer to access files over a network as easily as if the network devices were attached to its local disks. ...
Mac OS X In Mac OS X 10.4 and later, the HFS+ filesystem supports extended attributes. 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. Mac OS X (official IPA pronunciation: ) is a line of proprietary, graphical operating systems developed, marketed, and sold by Apple Inc. ...
HFS Plus or HFS+ is a file system developed by Apple Computer to replace their Hierarchical File System (HFS) as the primary file system used on Macintosh computers. ...
In various branches of mathematics and computer science, strings are sequences of various simple objects (symbols, tokens, characters, etc. ...
See also In computer file systems, a fork is additional data associated with a file system object. ...
Attribute-value pairs are a fundamental data representation in many computing systems and applications. ...
A file attribute is a piece of data that describes or is associated with a computer file. ...
External links - http://acl.bestbits.at/ - Linux Extended Attributes and ACLs or libattr
- Implementation of OS/2 extended attributes on the FAT file system
- The fsattr(5) man page for Solaris 10
- The SetFile(1) man page for OSX
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