1nbd_get_size(3)                     LIBNBD                     nbd_get_size(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 (struct nbd_handle *h);
12

DESCRIPTION

14       Returns the size in bytes of the NBD export.
15
16       This call does not block, because it returns data that is saved in the
17       handle from the NBD protocol handshake.
18

RETURN VALUE

20       This call returns a 64 bit signed integer ≥ 0.
21

ERRORS

23       On error "-1" is returned.
24
25       Refer to "ERROR HANDLING" in libnbd(3) for how to get further details
26       of the error.
27

HANDLE STATE

29       The handle must be negotiating, or connected with the server, or shut
30       down, otherwise this call will return an error.
31

VERSION

33       This function first appeared in libnbd 1.0.
34
35       If you need to test if this function is available at compile time check
36       if the following macro is defined:
37
38        #define LIBNBD_HAVE_NBD_GET_SIZE 1
39

EXAMPLE

41       This example is also available as examples/get-size.c in the libnbd
42       source code.
43
44        /* This example shows how to connect to an NBD
45         * server and read the size of the disk.
46         *
47         * You can test it with nbdkit like this:
48         *
49         * nbdkit -U - memory 1M \
50         *   --run './get-size $unixsocket'
51         */
52
53        #include <stdio.h>
54        #include <stdlib.h>
55        #include <stdint.h>
56        #include <inttypes.h>
57
58        #include <libnbd.h>
59
60        int
61        main (int argc, char *argv[])
62        {
63          struct nbd_handle *nbd;
64          int64_t size;
65
66          if (argc != 2) {
67            fprintf (stderr, "%s socket\n", argv[0]);
68            exit (EXIT_FAILURE);
69          }
70
71          /* Create the libnbd handle. */
72          nbd = nbd_create ();
73          if (nbd == NULL) {
74            fprintf (stderr, "%s\n", nbd_get_error ());
75            exit (EXIT_FAILURE);
76          }
77
78          /* Connect to the NBD server over a
79           * Unix domain socket.
80           */
81          if (nbd_connect_unix (nbd, argv[1]) == -1) {
82            fprintf (stderr, "%s\n", nbd_get_error ());
83            exit (EXIT_FAILURE);
84          }
85
86          /* Read the size in bytes and print it. */
87          size = nbd_get_size (nbd);
88          if (size == -1) {
89            fprintf (stderr, "%s\n", nbd_get_error ());
90            exit (EXIT_FAILURE);
91          }
92          printf ("%s: size = %" PRIi64 " bytes\n",
93                  argv[1], size);
94
95          /* Close the libnbd handle. */
96          nbd_close (nbd);
97
98          exit (EXIT_SUCCESS);
99        }
100

SEE ALSO

102       nbd_create(3), nbd_opt_info(3), "Size of the export" in libnbd(3),
103       libnbd(3).
104

AUTHORS

106       Eric Blake
107
108       Richard W.M. Jones
109

111       Copyright (C) 2019-2021 Red Hat Inc.
112

LICENSE

114       This library is free software; you can redistribute it and/or modify it
115       under the terms of the GNU Lesser General Public License as published
116       by the Free Software Foundation; either version 2 of the License, or
117       (at your option) any later version.
118
119       This library is distributed in the hope that it will be useful, but
120       WITHOUT ANY WARRANTY; without even the implied warranty of
121       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
122       Lesser General Public License for more details.
123
124       You should have received a copy of the GNU Lesser General Public
125       License along with this library; if not, write to the Free Software
126       Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
127       02110-1301 USA
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131libnbd-1.7.12                     2021-05-29                   nbd_get_size(3)
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