nbd_is_rotational(3)

1nbd_is_rotational(3)                LIBNBD                nbd_is_rotational(3)
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NAME

6       nbd_is_rotational - is the NBD disk rotational (like a disk)?
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SYNOPSIS

9        #include <libnbd.h>
10
11        int nbd_is_rotational (struct nbd_handle *h);
12

DESCRIPTION

14       Returns true if the disk exposed over NBD is rotational (like a
15       traditional floppy or hard disk).  Returns false if the disk has no
16       penalty for random access (like an SSD or RAM disk).
17
18       This call does not block, because it returns data that is saved in the
19       handle from the NBD protocol handshake.
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RETURN VALUE

22       This call returns a boolean value.
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ERRORS

25       On error "-1" is returned.
26
27       Refer to "ERROR HANDLING" in libnbd(3) for how to get further details
28       of the error.
29
30       The following parameters must not be NULL: "h".  For more information
31       see "Non-NULL parameters" in libnbd(3).
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HANDLE STATE

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

38       This function first appeared in libnbd 1.0.
39
40       If you need to test if this function is available at compile time check
41       if the following macro is defined:
42
43        #define LIBNBD_HAVE_NBD_IS_ROTATIONAL 1
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EXAMPLE

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

145       Eric Blake
146
147       Richard W.M. Jones
148

COPYRIGHT

150       Copyright (C) 2019-2021 Red Hat Inc.
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LICENSE

153       This library is free software; you can redistribute it and/or modify it
154       under the terms of the GNU Lesser General Public License as published
155       by the Free Software Foundation; either version 2 of the License, or
156       (at your option) any later version.
157
158       This library is distributed in the hope that it will be useful, but
159       WITHOUT ANY WARRANTY; without even the implied warranty of
160       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
161       Lesser General Public License for more details.
162
163       You should have received a copy of the GNU Lesser General Public
164       License along with this library; if not, write to the Free Software
165       Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
166       02110-1301 USA
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170libnbd-1.14.2                     2023-01-03              nbd_is_rotational(3)