1nbd_zero(3)                         LIBNBD                         nbd_zero(3)
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NAME

6       nbd_zero - send write zeroes command to the NBD server
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SYNOPSIS

9        #include <libnbd.h>
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11        int nbd_zero (struct nbd_handle *h, uint64_t count,
12                      uint64_t offset, uint32_t flags);
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DESCRIPTION

15       Issue a write zeroes command to the NBD server, which if supported by
16       the server causes a zeroes to be written efficiently starting at
17       "offset" and ending at "offset" + "count" - 1.  The call returns when
18       the command has been acknowledged by the server, or there is an error.
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20       The "flags" parameter may be 0 for no flags, or may contain
21       "LIBNBD_CMD_FLAG_FUA" meaning that the server should not return until
22       the data has been committed to permanent storage (if that is supported
23       - some servers cannot do this, see nbd_can_fua(3)),
24       "LIBNBD_CMD_FLAG_NO_HOLE" meaning that the server should favor writing
25       actual allocated zeroes over punching a hole, and/or
26       "LIBNBD_CMD_FLAG_FAST_ZERO" meaning that the server must fail quickly
27       if writing zeroes is no faster than a normal write (if that is
28       supported - some servers cannot do this, see nbd_can_fast_zero(3)).
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RETURN VALUE

31       If the call is successful the function returns 0.
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ERRORS

34       On error "-1" is returned.
35
36       Refer to "ERROR HANDLING" in libnbd(3) for how to get further details
37       of the error.
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HANDLE STATE

40       The handle must be connected and finished handshaking with the server,
41       otherwise this call will return an error.
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VERSION

44       This function first appeared in libnbd 1.0.
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46       If you need to test if this function is available at compile time check
47       if the following macro is defined:
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49        #define LIBNBD_HAVE_NBD_ZERO 1
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SEE ALSO

52       nbd_aio_zero(3), nbd_can_fast_zero(3), nbd_can_fua(3), nbd_can_zero(3),
53       nbd_create(3), libnbd(3).
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AUTHORS

56       Eric Blake
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58       Richard W.M. Jones
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61       Copyright (C) 2019 Red Hat Inc.
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LICENSE

64       This library is free software; you can redistribute it and/or modify it
65       under the terms of the GNU Lesser General Public License as published
66       by the Free Software Foundation; either version 2 of the License, or
67       (at your option) any later version.
68
69       This library is distributed in the hope that it will be useful, but
70       WITHOUT ANY WARRANTY; without even the implied warranty of
71       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
72       Lesser General Public License for more details.
73
74       You should have received a copy of the GNU Lesser General Public
75       License along with this library; if not, write to the Free Software
76       Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
77       02110-1301 USA
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81libnbd-1.3.7                      2020-04-23                       nbd_zero(3)
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