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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 accessible 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 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.

   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).



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