1nbd_get_size(3)                     LIBNBD                     nbd_get_size(3)
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3
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NAME

6       nbd_get_size - return the export size
7

SYNOPSIS

9        #include <libnbd.h>
10
11        int64_t nbd_get_size (
12                  struct nbd_handle *h
13                );
14

DESCRIPTION

16       Returns the size in bytes of the NBD export.
17
18       Note that this call fails with "EOVERFLOW" for an unlikely server that
19       advertises a size which cannot fit in a 64-bit signed integer.
20
21       This call does not block, because it returns data that is saved in the
22       handle from the NBD protocol handshake.
23

RETURN VALUE

25       This call returns a 64 bit signed integer ≥ 0.
26

ERRORS

28       On error -1 is returned.
29
30       Refer to "ERROR HANDLING" in libnbd(3) for how to get further details
31       of the error.
32
33       The following parameters must not be NULL: "h".  For more information
34       see "Non-NULL parameters" in libnbd(3).
35

HANDLE STATE

37       The handle must be negotiating, or connected with the server, or shut
38       down, otherwise this call will return an error.
39

VERSION

41       This function first appeared in libnbd 1.0.
42
43       If you need to test if this function is available at compile time check
44       if the following macro is defined:
45
46        #define LIBNBD_HAVE_NBD_GET_SIZE 1
47

EXAMPLE

49       This example is also available as examples/get-size.c in the libnbd
50       source code.
51
52        /* This example shows how to connect to an NBD
53         * server and read the size of the disk.
54         *
55         * You can test it with nbdkit like this:
56         *
57         * nbdkit -U - memory 1M \
58         *   --run './get-size $unixsocket'
59         */
60
61        #include <stdio.h>
62        #include <stdlib.h>
63        #include <stdint.h>
64        #include <inttypes.h>
65
66        #include <libnbd.h>
67
68        int
69        main (int argc, char *argv[])
70        {
71          struct nbd_handle *nbd;
72          int64_t size;
73
74          if (argc != 2) {
75            fprintf (stderr, "%s socket\n", argv[0]);
76            exit (EXIT_FAILURE);
77          }
78
79          /* Create the libnbd handle. */
80          nbd = nbd_create ();
81          if (nbd == NULL) {
82            fprintf (stderr, "%s\n", nbd_get_error ());
83            exit (EXIT_FAILURE);
84          }
85
86          /* Connect to the NBD server over a
87           * Unix domain socket.
88           */
89          if (nbd_connect_unix (nbd, argv[1]) == -1) {
90            fprintf (stderr, "%s\n", nbd_get_error ());
91            exit (EXIT_FAILURE);
92          }
93
94          /* Read the size in bytes and print it. */
95          size = nbd_get_size (nbd);
96          if (size == -1) {
97            fprintf (stderr, "%s\n", nbd_get_error ());
98            exit (EXIT_FAILURE);
99          }
100          printf ("%s: size = %" PRIi64 " bytes\n",
101                  argv[1], size);
102
103          /* Close the libnbd handle. */
104          nbd_close (nbd);
105
106          exit (EXIT_SUCCESS);
107        }
108

SEE ALSO

110       nbd_create(3), nbd_opt_info(3), "Size of the export" in libnbd(3),
111       libnbd(3).
112

AUTHORS

114       Eric Blake
115
116       Richard W.M. Jones
117

119       Copyright Red Hat
120

LICENSE

122       This library is free software; you can redistribute it and/or modify it
123       under the terms of the GNU Lesser General Public License as published
124       by the Free Software Foundation; either version 2 of the License, or
125       (at your option) any later version.
126
127       This library is distributed in the hope that it will be useful, but
128       WITHOUT ANY WARRANTY; without even the implied warranty of
129       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
130       Lesser General Public License for more details.
131
132       You should have received a copy of the GNU Lesser General Public
133       License along with this library; if not, write to the Free Software
134       Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
135       02110-1301 USA
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139libnbd-1.16.5                     2023-09-26                   nbd_get_size(3)
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