attr - Unix, Linux Command
attr - extended attributes on XFS filesystem objects
attr [ -LRSq ] -s attrname [ -V attrvalue ]
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.
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.
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
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.
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
They are the
user address spaces.
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.
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.
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:
-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.
-g attrname option tells
attr to search the named object and print (to stdout) the value
associated with that attribute name.
-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.
-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.
-q flag, stdout will be a simple list of only the attribute names,
one per line, suitable for input into a script.
-r attrname option tells
attr to remove an attribute with the given name from the object if the
There is no output on sucessful completion.
-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.
-V attrvalue flag, the attribute will be set to have a value of
attrvalue and stdin will not be read.
-q flag, stdout will not be used.
-q flag, a message showing the attribute name and the entire value
will be printed.
-R option is given and the process has appropriate privileges,
operate in the
root attribute namespace rather that the
USER attribute namespace.
-S option is similar, except it specifies use of the
security attribute namespace.
-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).
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.
getfattr provides a mechanism to retrieve all of the attribute names.