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.\" ========================================================================
.\"
.IX Title "nbd_get_size 3"
.TH nbd_get_size 3 2024-05-31 libnbd-1.20.0 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_get_size \- return the export size
.SH SYNOPSIS
.IX Header "SYNOPSIS"
.Vb 1
\& #include <libnbd.h>
\&
\& int64_t nbd_get_size (
\&           struct nbd_handle *h
\&         );
.Ve
.SH DESCRIPTION
.IX Header "DESCRIPTION"
Returns the size in bytes of the NBD export.
.PP
Note that this call fails with \f(CW\*(C`EOVERFLOW\*(C'\fR for an unlikely
server that advertises a size which cannot fit in a 64\-bit
signed integer.
.PP
\&\fBnbdinfo\fR\|(1) \fI\-\-size\fR option is a way to access this API
from shell scripts.
.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 64 bit signed integer ≥ \f(CW0\fR.
.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_get_size
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_GET_SIZE 1
.Ve
.SH EXAMPLE
.IX Header "EXAMPLE"
This example is also available as \fIexamples/get\-size.c\fR
in the libnbd source code.
.PP
.Vb 8
\& /* This example shows how to connect to an NBD
\&  * server and read the size of the disk.
\&  *
\&  * You can test it with nbdkit like this:
\&  *
\&  * nbdkit \-U \- memory 1M \e
\&  *   \-\-run \*(Aq./get\-size $unixsocket\*(Aq
\&  */
\&
\& #include <stdio.h>
\& #include <stdlib.h>
\& #include <stdint.h>
\& #include <inttypes.h>
\&
\& #include <libnbd.h>
\&
\& int
\& main (int argc, char *argv[])
\& {
\&   struct nbd_handle *nbd;
\&   int64_t size;
\&
\&   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);
\&   }
\&
\&   /* 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);
\&   }
\&
\&   /* Read the size in bytes and print it. */
\&   size = nbd_get_size (nbd);
\&   if (size == \-1) {
\&     fprintf (stderr, "%s\en", nbd_get_error ());
\&     exit (EXIT_FAILURE);
\&   }
\&   printf ("%s: size = %" PRIi64 " bytes\en",
\&           argv[1], size);
\&
\&   /* 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),
"Size of the export" in \fBlibnbd\fR\|(3),
\&\fBlibnbd\fR\|(3),
\&\fBnbdinfo\fR\|(1).
.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