Provided by: libattr1-dev_2.4.47-1ubuntu1_amd64 
NAME
attr_multi, attr_multif - manipulate multiple user attributes on a filesystem object at
once
C SYNOPSIS
#include <attr/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);
DESCRIPTION
The attr_multi and attr_multif functions provide a way to operate on multiple attributes
of a filesystem object at once.
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 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:
[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.
DIAGNOSTICS
On success, zero is returned. On error, -1 is returned, and errno is set appropriately.
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.
SEE ALSO
attr(1), attr_get(3), attr_list(3), attr_remove(3), and attr_set(3).