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ATTR(1)                      XFS Compatibility API                     ATTR(1)



NAME
       attr - extended attributes on XFS filesystem objects

SYNOPSIS
       attr [ -LRSq ] -s attrname [ -V attrvalue ] pathname

       attr [ -LRSq ] -g attrname pathname

       attr [ -LRSq ] -r attrname pathname

       attr [ -LRSq ] -l pathname


OVERVIEW
       Extended  attributes  implement  the  ability  for  a user to attach name:value pairs to objects within the XFS
       filesystem.

       This document describes the attr command, which is mostly compatible with the IRIX command of  the  same  name.
       It  is  thus  aimed specifically at users of the XFS filesystem - for filesystem independent extended attribute
       manipulation, consult the getfattr(1) and setfattr(1) documentation.

       Extended attributes can 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.

       In the XFS filesystem, 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 64KB
       of arbitrary binary data.

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

       XFS  uses 2 disjoint attribute name spaces associated with every filesystem object.  They are the root and user
       address spaces.  The root address space is accessable only to the superuser, and then only by specifying a flag
       argument  to  the  function call.  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.

DESCRIPTION
       The  attr utility allows the manipulation of extended attributes associated with filesystem objects from within
       shell scripts.

       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 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 sucessful 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 attr-
              value 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.

       The -S option is similar, except it specifies use of the security 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
       The  standard  file  interchange/archive  programs  tar(1),  and  cpio(1)  will not archive or restore extended
       attributes, while the xfsdump(8) program will.

CAVEATS
       The list option present in the IRIX version of this command is not supported.  getfattr provides a mechanism to
       retrieve all of the attribute names.

SEE ALSO
       getfattr(1), setfattr(1), attr_get(3), attr_set(3), attr_multi(3), attr_remove(3), attr(5), and xfsdump(8).



Dec 2001                      Extended Attributes                      ATTR(1)