Section: XFS Compatibility API (1)
Updated: Extended Attributes
attr - extended attributes on XFS filesystem objects
attr [ -LRSq ] -s attrname [ -V attrvalue ] pathname
attr [ -LRSq ] -g attrname pathname
attr [ -LRSq ] -r attrname pathname
attr [ -LRSq ] -l pathname
Extended attributes implement the ability for a user to attach
name:value pairs to objects within the XFS filesystem.
This document describes the
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
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
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.
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
They are the
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
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.
utility allows the manipulation of extended attributes associated with
filesystem objects from within shell scripts.
There are four main operations that
to search the named object and print (to stdout) the value
associated with that attribute name.
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.
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.
flag, stdout will be a simple list of only the attribute names,
one per line, suitable for input into a script.
to remove an attribute with the given name from the object if the
There is no output on successful completion.
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.
flag, the attribute will be set to have a value of
and stdin will not be read.
flag, stdout will not be used.
flag, a message showing the attribute name and the entire value
will be printed.
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.
option is given and the process has appropriate privileges,
operate in the
attribute namespace rather that the
option is similar, except it specifies use of the
option is given
will try to keep quiet.
It will output error messages (to stderr)
but will not print status messages (to stdout).
The standard file interchange/archive programs
will not archive or restore extended attributes,
The list option present in the IRIX version of this command is not supported.
provides a mechanism to retrieve all of the attribute names.