1nbd_create(3) LIBNBD nbd_create(3)
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3
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6 nbd_create, nbd_close, nbd_get_error, nbd_get_errno - create libnbd
7 handles and fetch errors
8
10 #include <libnbd.h>
11
12 struct nbd_handle *nbd;
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14 struct nbd_handle *nbd_create (void);
15 void nbd_close (struct nbd_handle *nbd);
16 const char *nbd_get_error (void);
17 int nbd_get_errno (void);
18
20 #include <libnbd.h>
21
22 main ()
23 {
24 struct nbd_handle *nbd;
25
26 nbd = nbd_create ();
27 if (nbd == NULL) {
28 fprintf (stderr, "%s\n", nbd_get_error ());
29 nbd_close (nbd);
30 exit (EXIT_FAILURE);
31 }
32 nbd_close (nbd);
33 exit (EXIT_SUCCESS);
34 }
35
36 cc prog.c -o prog -lnbd
37 or:
38 cc prog.c -o prog `pkg-config libnbd --cflags --libs`
39
41 Create and close handles
42 struct nbd_handle is an opaque structure which describes an NBD client
43 handle and the connection to an NBD server.
44
45 nbd_create creates a new handle. It returns a pointer to the opaque
46 handle structure.
47
48 On error this returns "NULL". See "ERROR HANDLING" in libnbd(3) for
49 how to get further details of the error.
50
51 nbd_close closes the handle and frees any associated resources. The
52 final status of any command that has not been retired (whether by
53 nbd_aio_command_completed(3) or by a low-level completion callback
54 returning 1) is lost. This function is not safe to call while any
55 other thread is still using any "nbd_*" API on the same handle. This
56 function can block in the case where we wait for a subprocess (eg. one
57 created with nbd_connect_command(3)).
58
59 Getting the latest error message in the thread
60 See "ERROR HANDLING" in libnbd(3) for more discussion of how error
61 handling works in libnbd.
62
63 nbd_get_error returns the most recent error message in the current
64 thread. The error message is only valid if called immediately after
65 the failing call, from the same thread. The error string returned will
66 be freed up next time any libnbd API is called from the same thread, so
67 if you need to keep it you must make a copy.
68
69 This should never return "NULL" provided there was an error returned
70 from the immediately preceding libnbd call in the current thread.
71
72 nbd_get_errno returns the most recent "errno" in the current thread.
73 Not all errors have corresponding errnos, so even if there has been an
74 error this may return 0. Error codes are the standard ones from
75 "<errno.h>".
76
78 libnbd(3).
79
81 Eric Blake
82
83 Richard W.M. Jones
84
86 Copyright (C) 2019 Red Hat Inc.
87
89 This library is free software; you can redistribute it and/or modify it
90 under the terms of the GNU Lesser General Public License as published
91 by the Free Software Foundation; either version 2 of the License, or
92 (at your option) any later version.
93
94 This library is distributed in the hope that it will be useful, but
95 WITHOUT ANY WARRANTY; without even the implied warranty of
96 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
97 Lesser General Public License for more details.
98
99 You should have received a copy of the GNU Lesser General Public
100 License along with this library; if not, write to the Free Software
101 Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
102 02110-1301 USA
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104
105
106libnbd-1.3.7 2020-04-23 nbd_create(3)