attr - manipulate Extended Attributes on filesystem objects
attr [ -LRq ] -s attrname [ -V attrvalue ] pathname
attr [ -LRq ] -g attrname pathname
attr [ -LRq ] -r attrname pathname
attr [ -LRq ] -l pathname
Extended Attributes implement the ability for a user to attach name/value
pairs to objects within the filesystem. They are currently only fully
supported in XFS and CXFS filesystems. Other filesystems may provide a
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.
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 256KB of arbitrary binary data.
Attributes can be attached to all types of inodes: regular files,
directories, symbolic links, device nodes, etc.
There are 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 privileged users, and only then by
specifying a flag argument to the function call. A privileged user can
be either the superuser in an IRIX environment, or a user with
CAP_DEVICE_MGT capability. 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.
Attributes are currently supported only in the XFS filesystem type.
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 [Toc] [Back]
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.
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
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
When the -R option is given and the process has appropriate privileges,
operate in the root attribute namespace rather that the USER attribute
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
The standard file interchange/archive programs tar(1), cpio(1), and
bru(1) will not archive or restore Extended Attributes, while the
xfsdump(1m) program will.
attr_get(2), attr_getf(2), attr_list(2), attr_listf(2), attr_multi(2),
attr_multif(2), attr_remove(2), attr_removef(2), attr_set(2),
PPPPaaaaggggeeee 2222 [ Back ]