Интерактивная система просмотра системных руководств (man-ов)
attr_multif (3)
>> attr_multif (3) ( Linux man: Библиотечные вызовы )
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.
[c p a]
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.
