FGETATTR(3C) Standard C Library Functions FGETATTR(3C)


NAME


fgetattr, fsetattr, getattrat, setattrat - get and set system attributes

SYNOPSIS


#include <fcntl.h>
#include <sys/types.h>
#include <attr.h>
#include <sys/nvpair.h>

int fgetattr(int fildes, xattr_view_t view,nvlist_t **response);


int fsetattr(int fildes, xattr_view_t view,nvlist_t *request)


int getattrat(int fildes, xattr_view_t view, const char *filename,
nvlist_t **response);


int setattrat(int fildes, xattr_view_t view, const char *filename,
nvlist_t *request);


DESCRIPTION


The fgetattr() function obtains an nvlist of system attribute information
about an open file object specified by the file descriptor fildes,
obtained from a successful open(2), creat(2), dup(2), fcntl(2), or
pipe(2) function.


The getattrat() function first opens the extended attribute file
specified by filename in the already opened file directory object
specified by fildes. It then retrieves an nvlist of system attributes and
their values from filename.


The response argument is allocated by either fgetattr() or getattrat().
The application must call nvlist_free(3NVPAIR) to deallocate the memory.


Upon successful completion, the nvlist will contain one nvpair for each
of the system attributes associated with view. The list of views and the
attributes associated with each view are listed below. Not all
underlying file systems support all views and all attributes. The nvlist
will not contain an nvpair for any attribute not supported by the
underlying filesystem.


The fsetattr() function uses the nvlist pointed to by request to update
one or more of the system attribute's information about an open file
object specified by the file descriptor fildes, obtained from a
successful open(), creat(), dup(), fcntl(), or pipe() function. The
setattrat() function first opens the extended attribute file specified by
filename in the already opened file directory object specified by fildes.
It then uses the nvlist pointed to by request to update one or more of
the system attributes of filename.


If completion is not successful then no system attribute information is
updated.


The following chart lists the supported views, attributes, and data
types for each view:


View Attribute Data type
-------------------------------------------------------------------------------------
XATTR_VIEW_READONLY A_FSID uint64_value
A_OPAQUE boolean_value
A_AV_SCANSTAMP uint8_array[]
XATTR_VIEW_READWRITE A_READONLY boolean_value
A_HIDDEN boolean_value
A_SYSTEM boolean_value
A_ARCHIVE boolean_value
A_CRTIME uint64_array[2]
A_NOUNLINK boolean_value
A_IMMUTABLE boolean_value
A_APPENDONLY boolean_value
A_NODUMP boolean_value
A_AV_QUARANTINED boolean_value
A_AV_MODIFIED boolean_value
A_OWNERSID nvlist composed of uint32_value and string
A_GROUPSID nvlist composed of uint32_value and string
A_OFFLINE boolean_value
A_SPARSE boolean_value


RETURN VALUES


Upon successful completion, 0 is returned. Otherwise, -1 is returned and
errno is set to indicate the error.

ERRORS


The fgetattr(), getattrat(), fsetattr(), and setattrat(), functions will
fail if:

EBADF
The fildes argument is not a valid open file descriptor.


EINVAL
The underlying file system does not support extended file
attributes.


EIO
An error occurred while reading from the file system.


The getattrat() and setattrat() functions will fail if:

EACCES
Search permission or write permission for filename is denied.


ENOENT
The filename argument does not name an existing file in the
extended attribute directory represented by fildes.


EPERM
There are insufficient privileges to manipulate attributes.


EXAMPLES


Example 1: Obtain an nvlist of readonly system attributes for an open file


object.


Use fgetattr() to obtain an nvlist of the readonly system attributes for
the open file object represented by file descriptor fildes.


#include <fcntl.h>
#include <sys/types.h>
#include <attr.h>
#include <sys/nvpair.h>

nvlist_t *response;
nvpair_t *pair = NULL;

if (fgetattr(fildes, XATTR_VIEW_READONLY, &response)) {
exit(1);
}
while (pair = nvlist_next_nvpair(response, pair)) {
.
.
.
}
nvlist_free(response);


Example 2: Set the A_READONLY system attribute on an open file object.




Use fsetattr() to set the A_OPAQUE system attribute on the open file
object represented by file descriptor fildes.


nvlist_t *request;
nvpair_t *pair = NULL;

if (nvlist_alloc(&request, NV_UNIQUE_NAME, 0) != 0) {
exit(1);
}
if (nvlist_add_boolean_value(request, A_READONLY, 1) != 0) {
exit(1);
}
if (fsetattr(fildes, XATTR_VIEW_READWRITE, request)) {
exit(1);
}


Example 3: Obtain an nvlist of the read/write system attributes for a


file.


Use getattrat() to obtain an nvlist of the read/write system attributes
for the file named xattrfile in the extended attribute directory of the
open file represented by file descriptor fildes.


nvlist_t *response;
nvpair_t *pair = NULL;

if (getattrat(fildes, XATTR_VIEW_READWRITE, "file", &response)) {
exit(1);
}
while (pair = nvlist_next_nvpair(response, pair)) {
.
.
.
}
nvlist_free(response);


Example 4: Set the A_APPENDONLY system attribute on a file.




Use setattrat() to set the A_APPENDONLY system attribute on the file
named file in the extended attribute directory of the open file
represented by file descriptor fildes.


nvlist_t *request;
nvpair_t *pair = NULL;

if (nvlist_alloc(&request, NV_UNIQUE_NAME, 0) != 0) {
exit(1);
}
if (nvlist_add_boolean_value(request, A_APPENDONLY, 1) != 0) {
exit(1);
}
if (setattrat(fildes, XATTR_VIEW_READWRITE, "file", request)) {
exit(1);
}


ATTRIBUTES


See attributes(5) for descriptions of the following attributes:


+--------------------+-----------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-----------------+
|Interface Stability | Committed |
+--------------------+-----------------+
|MT-Level | Safe |
+--------------------+-----------------+

SEE ALSO


creat(2), dup(2), fcntl(2), fstat(2), fstatat(2), open(2), pipe(2),
libnvpair(3LIB), attributes(5), fsattr(5)


November 24, 2014 FGETATTR(3C)