attr(1) - man - phpman

ATTR(1)                                 XFS Compatibility API                                ATTR(1)



NAME
       attr - extended attributes on 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 filesystem.

       This document describes the attr command, which is mostly compatible with the IRIX command of
       the  same  name.   It  was originally aimed specifically at users of the XFS filesystem, even
       though it can be used now on any filesystem that supports extended attributes,  but  for  the
       generic  and  more portable interface for filesystem independent extended attribute manipula‐
       tion, consult the getfattr(1) and setfattr(1) documentation.

       Extended attributes can be used to store meta-information about the file.  For example "char‐
       acter-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 reso‐
       lution graphic image.

       In supported filesystems, 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 inodes: regular files, directories, symbolic
       links, device nodes, etc.

       Extended attributes use 2 disjoint attribute name spaces associated with every filesystem ob‐
       ject.   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 ad‐
       dress 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 pro‐
              cessing 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 at‐
       tributes 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 re‐
       store extended attributes, while the xfsdump(8) program will.

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

AUTHOR
       Andreas  Gruenbacher,  <andreas.gruenbacher AT gmail.com>  and  the  SGI  XFS  development team,
       <linux-xfs AT oss.com>.

       Please send your bug reports or comments to <https://savannah.nongnu.org/bugs/?group=attr> or
       <acl-devel AT nongnu.org>.

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



Dec 2001                                 Extended Attributes                                 ATTR(1)