1nbd_is_rotational(3) LIBNBD nbd_is_rotational(3)
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6 nbd_is_rotational - is the NBD disk rotational (like a disk)?
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9 #include <libnbd.h>
10
11 int nbd_is_rotational (
12 struct nbd_handle *h
13 );
14
16 Returns true if the disk exposed over NBD is rotational (like a
17 traditional floppy or hard disk). Returns false if the disk has no
18 penalty for random access (like an SSD or RAM disk).
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20 This call does not block, because it returns data that is saved in the
21 handle from the NBD protocol handshake.
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24 This call returns a boolean value.
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27 On error -1 is returned.
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29 Refer to "ERROR HANDLING" in libnbd(3) for how to get further details
30 of the error.
31
32 The following parameters must not be NULL: "h". For more information
33 see "Non-NULL parameters" in libnbd(3).
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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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40 This function first appeared in libnbd 1.0.
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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_IS_ROTATIONAL 1
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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
132 /* Added in 1.2 */
133 PRINT_FLAG (nbd_can_fast_zero);
134 #endif
135 #if LIBNBD_HAVE_NBD_CAN_BLOCK_STATUS_PAYLOAD
136 /* Added in 1.18 */
137 PRINT_FLAG (nbd_can_block_status_payload);
138 #endif
139 PRINT_FLAG (nbd_is_read_only);
140 PRINT_FLAG (nbd_is_rotational);
141
142 /* Close the libnbd handle. */
143 nbd_close (nbd);
144
145 exit (EXIT_SUCCESS);
146 }
147
149 nbd_create(3), nbd_opt_info(3), "Flag calls" in libnbd(3), libnbd(3).
150
152 Eric Blake
153
154 Richard W.M. Jones
155
157 Copyright Red Hat
158
160 This library is free software; you can redistribute it and/or modify it
161 under the terms of the GNU Lesser General Public License as published
162 by the Free Software Foundation; either version 2 of the License, or
163 (at your option) any later version.
164
165 This library is distributed in the hope that it will be useful, but
166 WITHOUT ANY WARRANTY; without even the implied warranty of
167 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
168 Lesser General Public License for more details.
169
170 You should have received a copy of the GNU Lesser General Public
171 License along with this library; if not, write to the Free Software
172 Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
173 02110-1301 USA
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177libnbd-1.18.1 2023-10-31 nbd_is_rotational(3)