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.\" ========================================================================
.\"
.IX Title "nbd_can_fua 3"
.TH nbd_can_fua 3 2024-05-08 libnbd-1.20.1 LIBNBD
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH NAME
nbd_can_fua \- does the server support the FUA flag?
.SH SYNOPSIS
.IX Header "SYNOPSIS"
.Vb 1
\& #include <libnbd.h>
\&
\& int nbd_can_fua (
\&       struct nbd_handle *h
\&     );
.Ve
.SH DESCRIPTION
.IX Header "DESCRIPTION"
Returns true if the server supports the FUA flag on
certain commands (see \fBnbd_pwrite\fR\|(3)).
.PP
This call does not block, because it returns data that is saved in
the handle from the NBD protocol handshake.
.SH "RETURN VALUE"
.IX Header "RETURN VALUE"
This call returns a boolean value.
.SH ERRORS
.IX Header "ERRORS"
On error \f(CW\-1\fR is returned.
.PP
Refer to "ERROR HANDLING" in \fBlibnbd\fR\|(3)
for how to get further details of the error.
.PP
The following parameters must not be NULL: \f(CW\*(C`h\*(C'\fR.
For more information see "Non-NULL parameters" in \fBlibnbd\fR\|(3).
.SH "HANDLE STATE"
.IX Header "HANDLE STATE"
nbd_can_fua
can be called when the handle is in the following states:
.PP
.Vb 8
\& ┌─────────────────────────────────────┬─────────────────────────┐
\& │ Handle created, before connecting   │ ❌ error                │
\& │ Connecting                          │ ❌ error                │
\& │ Connecting & handshaking (opt_mode) │ ✅ allowed              │
\& │ Connected to the server             │ ✅ allowed              │
\& │ Connection shut down                │ ✅ allowed              │
\& │ Handle dead                         │ ❌ error                │
\& └─────────────────────────────────────┴─────────────────────────┘
.Ve
.SH VERSION
.IX Header "VERSION"
This function first appeared in libnbd 1.0.
.PP
If you need to test if this function is available at compile time
check if the following macro is defined:
.PP
.Vb 1
\& #define LIBNBD_HAVE_NBD_CAN_FUA 1
.Ve
.SH EXAMPLE
.IX Header "EXAMPLE"
This example is also available as \fIexamples/server\-flags.c\fR
in the libnbd source code.
.PP
.Vb 8
\& /* This example shows how to connect to an NBD
\&  * server and print the export flags.
\&  *
\&  * You can test it with nbdkit like this:
\&  *
\&  * nbdkit \-U \- memory 1M \e
\&  *   \-\-run \*(Aq./server\-flags $unixsocket\*(Aq
\&  */
\&
\& #include <stdio.h>
\& #include <stdlib.h>
\& #include <stdbool.h>
\&
\& #include <libnbd.h>
\&
\& int
\& main (int argc, char *argv[])
\& {
\&   struct nbd_handle *nbd;
\&   char *str;
\&   int flag;
\&
\&   if (argc != 2) {
\&     fprintf (stderr, "%s socket\en", argv[0]);
\&     exit (EXIT_FAILURE);
\&   }
\&
\&   /* Create the libnbd handle. */
\&   nbd = nbd_create ();
\&   if (nbd == NULL) {
\&     fprintf (stderr, "%s\en", nbd_get_error ());
\&     exit (EXIT_FAILURE);
\&   }
\&
\&   /* Request full information. */
\& #if LIBNBD_HAVE_NBD_SET_FULL_INFO /* Added in 1.4 */
\&   if (nbd_set_full_info (nbd, true) == \-1) {
\&     fprintf (stderr, "%s\en", nbd_get_error ());
\&     exit (EXIT_FAILURE);
\&   }
\& #endif
\&
\&   /* Connect to the NBD server over a
\&    * Unix domain socket.
\&    */
\&   if (nbd_connect_unix (nbd, argv[1]) == \-1) {
\&     fprintf (stderr, "%s\en", nbd_get_error ());
\&     exit (EXIT_FAILURE);
\&   }
\&
\&   /* See if the server provided extra details,
\&    * using functions added in 1.4
\&    */
\& #if LIBNBD_HAVE_NBD_GET_EXPORT_DESCRIPTION
\&   str = nbd_get_canonical_export_name (nbd);
\&   if (str)
\&     printf ("canonical_name = %s\en", str);
\&   free (str);
\&   str = nbd_get_export_description (nbd);
\&   if (str)
\&     printf ("description = %s\en", str);
\&   free (str);
\& #endif
\&
\&   /* Read and print the flags. */
\& #define PRINT_FLAG(flag_fn)                     \e
\&   flag = flag_fn (nbd);                         \e
\&   if (flag == \-1) {                             \e
\&     fprintf (stderr, "%s\en", nbd_get_error ()); \e
\&     exit (EXIT_FAILURE);                        \e
\&   }                                             \e
\&   printf (#flag_fn " = %s\en",                   \e
\&           flag ? "true" : "false");
\&
\&   PRINT_FLAG (nbd_can_cache);
\&   PRINT_FLAG (nbd_can_df);
\&   PRINT_FLAG (nbd_can_flush);
\&   PRINT_FLAG (nbd_can_fua);
\&   PRINT_FLAG (nbd_can_multi_conn);
\&   PRINT_FLAG (nbd_can_trim);
\&   PRINT_FLAG (nbd_can_zero);
\& #if LIBNBD_HAVE_NBD_CAN_FAST_ZERO
\&   /* Added in 1.2 */
\&   PRINT_FLAG (nbd_can_fast_zero);
\& #endif
\& #if LIBNBD_HAVE_NBD_CAN_BLOCK_STATUS_PAYLOAD
\&   /* Added in 1.18 */
\&   PRINT_FLAG (nbd_can_block_status_payload);
\& #endif
\&   PRINT_FLAG (nbd_is_read_only);
\&   PRINT_FLAG (nbd_is_rotational);
\&
\&   /* Close the libnbd handle. */
\&   nbd_close (nbd);
\&
\&   exit (EXIT_SUCCESS);
\& }
.Ve
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBnbd_create\fR\|(3),
\&\fBnbd_opt_info\fR\|(3),
\&\fBnbd_pwrite\fR\|(3),
\&\fBnbd_trim\fR\|(3),
\&\fBnbd_zero\fR\|(3),
"Flag calls" in \fBlibnbd\fR\|(3),
\&\fBlibnbd\fR\|(3).
.SH AUTHORS
.IX Header "AUTHORS"
Eric Blake
.PP
Richard W.M. Jones
.SH COPYRIGHT
.IX Header "COPYRIGHT"
Copyright Red Hat
.SH LICENSE
.IX Header "LICENSE"
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2 of the License, or (at your option) any later version.
.PP
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
Lesser General Public License for more details.
.PP
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110\-1301 USA