Проект OpenNet: MAN fgetattr (3) Библиотечные вызовы (FreeBSD и Linux)

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fgetattr (3)

>> fgetattr (3) ( Solaris man: Библиотечные вызовы )

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

XATTR_VIEW_READWRITE

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);
    }