nbd_get_canonical_export_name(3)

1nbd_get_canonical_export_name(3)    LIBNBD    nbd_get_canonical_export_name(3)
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NAME

6       nbd_get_canonical_export_name - return the canonical export name, if
7       the server has one
8

SYNOPSIS

10        #include <libnbd.h>
11
12        char * nbd_get_canonical_export_name (struct nbd_handle *h);
13

DESCRIPTION

15       The NBD protocol permits a server to report an optional canonical
16       export name, which may differ from the client's request (as set by
17       nbd_set_export_name(3) or nbd_connect_uri(3)).  This function accesses
18       any name returned by the server; it may be the same as the client
19       request, but is more likely to differ when the client requested a
20       connection to the default export name (an empty string "").
21
22       Some servers are unlikely to report a canonical name unless the client
23       specifically hinted about wanting it, via nbd_set_full_info(3).
24

RETURN VALUE

26       This call returns a string.  The caller must free the returned string
27       to avoid a memory leak.
28

ERRORS

30       On error "NULL" is returned.
31
32       Refer to "ERROR HANDLING" in libnbd(3) for how to get further details
33       of the error.
34

HANDLE STATE

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

40       This function first appeared in libnbd 1.4.
41
42       If you need to test if this function is available at compile time check
43       if the following macro is defined:
44
45        #define LIBNBD_HAVE_NBD_GET_CANONICAL_EXPORT_NAME 1
46

EXAMPLE

48       This example is also available as examples/server-flags.c in the libnbd
49       source code.
50
51        /* This example shows how to connect to an NBD
52         * server and print the export flags.
53         *
54         * You can test it with nbdkit like this:
55         *
56         * nbdkit -U - memory 1M \
57         *   --run './server-flags $unixsocket'
58         */
59
60        #include <stdio.h>
61        #include <stdlib.h>
62
63        #include <libnbd.h>
64
65        int
66        main (int argc, char *argv[])
67        {
68          struct nbd_handle *nbd;
69          char *str;
70          int flag;
71
72          if (argc != 2) {
73            fprintf (stderr, "%s socket\n", argv[0]);
74            exit (EXIT_FAILURE);
75          }
76
77          /* Create the libnbd handle. */
78          nbd = nbd_create ();
79          if (nbd == NULL) {
80            fprintf (stderr, "%s\n", nbd_get_error ());
81            exit (EXIT_FAILURE);
82          }
83
84          /* Request full information. */
85        #if LIBNBD_HAVE_NBD_SET_FULL_INFO /* Added in 1.4 */
86          if (nbd_set_full_info (nbd, true) == -1) {
87            fprintf (stderr, "%s\n", nbd_get_error ());
88            exit (EXIT_FAILURE);
89          }
90        #endif
91
92          /* Connect to the NBD server over a
93           * Unix domain socket.
94           */
95          if (nbd_connect_unix (nbd, argv[1]) == -1) {
96            fprintf (stderr, "%s\n", nbd_get_error ());
97            exit (EXIT_FAILURE);
98          }
99
100          /* See if the server provided extra details,
101           * using functions added in 1.4
102           */
103        #if LIBNBD_HAVE_NBD_GET_EXPORT_DESCRIPTION
104          str = nbd_get_canonical_export_name (nbd);
105          if (str)
106            printf ("canonical_name = %s\n", str);
107          free (str);
108          str = nbd_get_export_description (nbd);
109          if (str)
110            printf ("description = %s\n", str);
111          free (str);
112        #endif
113
114          /* Read and print the flags. */
115        #define PRINT_FLAG(flag_fn)                     \
116          flag = flag_fn (nbd);                         \
117          if (flag == -1) {                             \
118            fprintf (stderr, "%s\n", nbd_get_error ()); \
119            exit (EXIT_FAILURE);                        \
120          }                                             \
121          printf (#flag_fn " = %s\n",                   \
122                  flag ? "true" : "false");
123
124          PRINT_FLAG (nbd_can_cache);
125          PRINT_FLAG (nbd_can_df);
126          PRINT_FLAG (nbd_can_flush);
127          PRINT_FLAG (nbd_can_fua);
128          PRINT_FLAG (nbd_can_multi_conn);
129          PRINT_FLAG (nbd_can_trim);
130          PRINT_FLAG (nbd_can_zero);
131        #if LIBNBD_HAVE_NBD_CAN_FAST_ZERO /* Added in 1.2 */
132          PRINT_FLAG (nbd_can_fast_zero);
133        #endif
134          PRINT_FLAG (nbd_is_read_only);
135          PRINT_FLAG (nbd_is_rotational);
136
137          /* Close the libnbd handle. */
138          nbd_close (nbd);
139
140          exit (EXIT_SUCCESS);
141        }
142

AUTHORS

149       Eric Blake
150
151       Richard W.M. Jones
152

COPYRIGHT

154       Copyright (C) 2019-2020 Red Hat Inc.
155

LICENSE

157       This library is free software; you can redistribute it and/or modify it
158       under the terms of the GNU Lesser General Public License as published
159       by the Free Software Foundation; either version 2 of the License, or
160       (at your option) any later version.
161
162       This library is distributed in the hope that it will be useful, but
163       WITHOUT ANY WARRANTY; without even the implied warranty of
164       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
165       Lesser General Public License for more details.
166
167       You should have received a copy of the GNU Lesser General Public
168       License along with this library; if not, write to the Free Software
169       Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
170       02110-1301 USA
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174libnbd-1.6.2                      2021-03-02  nbd_get_canonical_export_name(3)