attr_multif man page on IRIX

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ATTR_MULTI(2)							 ATTR_MULTI(2)

NAME
     attr_multi, attr_multif - manipulate multiple user attributes on a
     filesystem object at once

C SYNOPSIS
     #include <sys/attributes.h>

     int attr_multi (const char *path, attr_multiop_t *oplist,
		     int count, int flags);

     int attr_multif (int fd, attr_multiop_t *oplist,
		      int count, int flags);

OVERVIEW
     The attr group of system calls implement the ability for a user to attach
     name/value pairs to objects within the 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.

     The names can be up to MAXNAMELEN 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 ATTR_MAX_VALUELEN (currently 64KB) 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 fully supported only in the XFS, CXFS and UDF
     filesystem types.	Other filesystem types may provide a partial
     implementation.

DESCRIPTION
     The attr_multi and attr_multif functions provide a way to operate on
     multiple attributes of a filesystem object at once.

									Page 1

ATTR_MULTI(2)							 ATTR_MULTI(2)

     Path points to a path name for a filesystem object, and fd refers to the
     file descriptor associated with a file.  The oplist is an array of
     attr_multiop_t structures.	 Each element in that array describes a single
     attribute operation and provides all the information required to carry
     out that operation and to check for success or failure of that operation.
     Count tells how many elements are in the oplist array.

     The contents of an attr_multiop_t structure include the following
     members:

	int am_opcode; /* which operation to perform (see below) */
	int am_error; /* [out arg] result of this sub-op (an errno) */
	char *am_attrname; /* attribute name to work with */
	char *am_attrvalue; /* [in/out arg] attribute value (raw bytes) */
	int am_length; /* [in/out arg] length of value */
	int am_flags; /* flags (bit-wise OR of #defines below) */

     The am_opcode field defines how the remaining fields are to be
     interpreted and can take on one of the following values:

	ATTR_OP_GET /* return the indicated attr's value */
	ATTR_OP_SET /* set/create the indicated attr/value pair */
	ATTR_OP_REMOVE /* remove the indicated attr */

     The am_error field will contain the appropriate error result code if that
     sub-operation fails.  The result codes for a given sub-operation are a
     subset of the result codes that are possible from the corresponding
     single-attribute function call.  For example, the result code possible
     from an ATTR_OP_GET sub-operation are a subset of those that can be
     returned from an attr_get function call.

     The am_attrname field is a pointer to a NULL terminated string giving the
     attribute name that the sub-operation should operate on.

     The am_attrvalue, am_length and am_flags fields are used to store the
     value of the named attribute, and some control flags for that sub-
     operation, respectively.  Their use varies depending on the value of the
     am_opcode field.

     ATTR_OP_GET
	  The am_attrvalue field is a pointer to a empty buffer that will be
	  overwritten with the value of the named attribute.  The am_length
	  field is initially the total size of the memory buffer that the
	  am_attrvalue field points to.	 After the operation, the am_length
	  field contains the actual size of the attribute's value.  The
	  am_flags field may be set to the ATTR_ROOT flag.  If the process has
	  appropriate priviledges, the ROOT namespace will be searched for the
	  named attribute, otherwise the USER namespace will be searched.

     ATTR_OP_SET
	  The am_attrvalue and am_length fields contain the new value for the
	  given attribute name and its length.	The ATTR_ROOT flag may be set

									Page 2

ATTR_MULTI(2)							 ATTR_MULTI(2)

	  in the am_flags field.  If the process has appropriate priviledges,
	  the ROOT namespace will be searched for the named attribute,
	  otherwise the USER namespace will be searched.  The ATTR_CREATE and
	  the ATTR_REPLACE flags may also be set in the am_flags field (but
	  not simultaneously).	If the ATTR_CREATE flag is set, the sub-
	  operation will set the am_error field to EEXIST if the named
	  attribute already exists.  If the ATTR_REPLACE flag is set, the
	  sub-operation will set the am_error field to ENOATTR if the named
	  attribute does not already exist.  If neither of those two flags are
	  set and the attribute does not exist, then the attribute will be
	  created with the given value.	 If neither of those two flags are set
	  and the attribute already exists, then the value will be replaced
	  with the given value.

     ATTR_OP_REMOVE
	  The am_attrvalue and am_length fields are not used and are ignored.
	  The am_flags field may be set to the ATTR_ROOT flag.	If the process
	  has appropriate priviledges, the ROOT namespace will be searched for
	  the named attribute, otherwise the USER namespace will be searched.

     The flags argument to the attr_multi call is used to control following of
     symbolic links in the path argument.  The default is to follow symbolic
     links, flags should be set to ATTR_DONTFOLLOW to not follow symbolic
     links.

     attr_multi will fail if one or more of the following are true:

     [ENOENT]	      The named file does not exist.

     [EPERM]	      The effective user ID does not match the owner of the
		      file and the effective user ID is not super-user.

     [ENOTDIR]	      A component of the path prefix is not a directory.

     [EACCES]	      Search permission is denied on a component of the path
		      prefix.

     [EINVAL]	      A bit other than ATTR_DONTFOLLOW was set in the flag
		      argument.

     [EFAULT]	      Path, or oplist points outside the allocated address
		      space of the process.

     [ELOOP]	      A path name lookup involved too many symbolic links.

     [ENAMETOOLONG]   The length of path exceeds {MAXPATHLEN}, or a pathname
		      component is longer than {MAXNAMELEN}.

     attr_multif will fail if:

									Page 3

ATTR_MULTI(2)							 ATTR_MULTI(2)

     [EINVAL]	    A bit was set in the flag argument, or fd refers to a
		    socket, not a file.

     [EFAULT]	    Oplist points outside the allocated address space of the
		    process.

     [EBADF]	    Fd does not refer to a valid descriptor.

SEE ALSO
     attr(1),
     attr_get(2), attr_getf(2),
     attr_list(2), attr_list(2)
     attr_remove(2), attr_removef(2),
     attr_set(2), attr_set(2)

DIAGNOSTICS
     Upon successful completion of the attr_multi call, a value of 0 is
     returned.	Otherwise, a value of -1 is returned and errno is set to
     indicate the error.  Note that the individual operations listed in the
     oplist array each have their own error return fields.  The errno variable
     only records the result of the attr_multi call itself, not the result of
     any of the sub-operations.

									Page 4

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