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);
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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.
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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.
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HANDLE STATE

29       The handle must be connected and finished handshaking with the server,
30       or shut down, otherwise this call will return an error.
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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       "Size of the export" in libnbd(3), nbd_create(3), libnbd(3).
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AUTHORS

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

110       Copyright (C) 2019 Red Hat Inc.
111

LICENSE

113       This library is free software; you can redistribute it and/or modify it
114       under the terms of the GNU Lesser General Public License as published
115       by the Free Software Foundation; either version 2 of the License, or
116       (at your option) any later version.
117
118       This library is distributed in the hope that it will be useful, but
119       WITHOUT ANY WARRANTY; without even the implied warranty of
120       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
121       Lesser General Public License for more details.
122
123       You should have received a copy of the GNU Lesser General Public
124       License along with this library; if not, write to the Free Software
125       Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
126       02110-1301 USA
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130libnbd-1.2.1                      2019-11-14                   nbd_get_size(3)
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