attr(1)								       attr(1)

NAME    [Toc]    [Back]

     attr - manipulate Extended	Attributes on filesystem objects

SYNOPSIS    [Toc]    [Back]

     attr [ -LRq ] -s attrname [ -V attrvalue ]	pathname

     attr [ -LRq ] -g attrname pathname

     attr [ -LRq ] -r attrname pathname

     attr [ -LRq ] -l pathname

OVERVIEW    [Toc]    [Back]

     Extended Attributes implement the ability for a user to attach name/value
     pairs to objects within the filesystem.  They are currently only fully
     supported in XFS and CXFS filesystems.  Other filesystems may provide a
     partial implementation.

     They could	be used	to store meta-information about	the file.  For example
     "character-set=kanji" could tell a	document browser to use	the Kanji
     character set when	displaying that	document and "thumbnail=..." could
     provide a reduced resolution overview of a	high resolution	graphic	image.

     The names can be up to 256	bytes in length, terminated by the first 0
     byte.  The	intent is that they be printable ASCII (or other character
     set) names	for the	attribute.

     The values	can be up to 256KB of arbitrary	binary data.

     Attributes	can be attached	to all types of	inodes:	 regular files,
     directories, symbolic links, device nodes,	etc.

     There are 2 disjoint attribute name spaces	associated with	every
     filesystem	object.	 They are the root and user address spaces.  The root
     address space is accessible only to privileged users, and only then by
     specifying	a flag argument	to the function	call.  A privileged user can
     be	either the superuser in	an IRIX	environment, or	a user with
     CAP_DEVICE_MGT capability.	 Other users will not see or be	able to	modify
     attributes	in the root address space.  The	user address space is
     protected by the normal file permissions mechanism, so the	owner of the
     file can decide who is able to see	and/or modify the value	of attributes
     on	any particular file.

     Attributes	are currently supported	only in	the XFS	filesystem type.

DESCRIPTION    [Toc]    [Back]

     The attr utility allows the manipulation of Extended Attributes
     associated	with filesystem	objects	from within shell scripts.






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attr(1)								       attr(1)



     There are four main operations that attr can perform:

     GET  The -g attrname option tells attr to search the named	object and
	  print	(to stdout) the	value associated with that attribute name.
	  With the -q flag, stdout will	be exactly and only the	value of the
	  attribute, suitable for storage directly into	a file or processing
	  via a	piped command.

     LIST The -l option	tells attr to list the names of	all the	attributes
	  that are associated with the object, and the number of bytes in the
	  value	of each	of those attributes.  With the -q flag,	stdout will be
	  a simple list	of only	the attribute names, one per line, suitable
	  for input into a script.

     REMOVE    [Toc]    [Back]
	  The -r attrname option tells attr to remove an attribute with	the
	  given	name from the object if	the attribute exists.  There is	no
	  output on successful completion.

     SET/CREATE
	  The -s attrname option tells attr to set the named attribute of the
	  object to the	value read from	stdin.	If an attribute	with that name
	  already exists, its value will be replaced with this one.  If	an
	  attribute with that name does	not already exist, one will be created
	  with this value.  With the -V	attrvalue flag,	the attribute will be
	  set to have a	value of attrvalue and stdin will not be read.	With
	  the -q flag, stdout will not be used.	 Without the -q	flag, a
	  message showing the attribute	name and the entire value will be
	  printed.

     When the -L option	is given and the named object is a symbolic link,
     operate on	the attributes of the object referenced	by the symbolic	link.
     Without this option, operate on the attributes of the symbolic link
     itself.

     When the -R option	is given and the process has appropriate privileges,
     operate in	the root attribute namespace rather that the USER attribute
     namespace.

     When the -q option	is given attr will try to keep quiet.  It will output
     error messages (to	stderr)	but will not print status messages (to
     stdout).

NOTES    [Toc]    [Back]

     The standard file interchange/archive programs tar(1), cpio(1), and
     bru(1) will not archive or	restore	Extended Attributes, while the
     xfsdump(1m) program will.

SEE ALSO    [Toc]    [Back]

     attr_get(2), attr_getf(2),	attr_list(2), attr_listf(2), attr_multi(2),
     attr_multif(2), attr_remove(2), attr_removef(2), attr_set(2),
     attr_setf(2), xfsdump(1m).


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