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=head1 NAME
nbd_get_size - return the export size
=head1 SYNOPSIS
#include <libnbd.h>
int64_t nbd_get_size (
struct nbd_handle *h
);
=head1 DESCRIPTION
Returns the size in bytes of the NBD export.
Note that this call fails with C<EOVERFLOW> for an unlikely
server that advertises a size which cannot fit in a 64-bit
signed integer.
L<nbdinfo(1)> I<--size> option is a way to access this API
from shell scripts.
This call does not block, because it returns data that is saved in
the handle from the NBD protocol handshake.
=head1 RETURN VALUE
This call returns a 64 bit signed integer E<ge> C<0>.
=head1 ERRORS
On error C<-1> is returned.
Refer to L<libnbd(3)/ERROR HANDLING>
for how to get further details of the error.
The following parameters must not be NULL: C<h>.
For more information see L<libnbd(3)/Non-NULL parameters>.
=head1 HANDLE STATE
nbd_get_size
can be called when the handle is in the following states:
┌─────────────────────────────────────┬─────────────────────────┐
│ Handle created, before connecting │ ❌ error │
│ Connecting │ ❌ error │
│ Connecting & handshaking (opt_mode) │ ✅ allowed │
│ Connected to the server │ ✅ allowed │
│ Connection shut down │ ✅ allowed │
│ Handle dead │ ❌ error │
└─────────────────────────────────────┴─────────────────────────┘
=head1 VERSION
This function first appeared in libnbd 1.0.
If you need to test if this function is available at compile time
check if the following macro is defined:
#define LIBNBD_HAVE_NBD_GET_SIZE 1
=head1 EXAMPLE
This example is also available as F<examples/get-size.c>
in the libnbd source code.
/* This example shows how to connect to an NBD
* server and read the size of the disk.
*
* You can test it with nbdkit like this:
*
* nbdkit -U - memory 1M \
* --run './get-size $unixsocket'
*/
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <inttypes.h>
#include <libnbd.h>
int
main (int argc, char *argv[])
{
struct nbd_handle *nbd;
int64_t size;
if (argc != 2) {
fprintf (stderr, "%s socket\n", argv[0]);
exit (EXIT_FAILURE);
}
/* Create the libnbd handle. */
nbd = nbd_create ();
if (nbd == NULL) {
fprintf (stderr, "%s\n", nbd_get_error ());
exit (EXIT_FAILURE);
}
/* Connect to the NBD server over a
* Unix domain socket.
*/
if (nbd_connect_unix (nbd, argv[1]) == -1) {
fprintf (stderr, "%s\n", nbd_get_error ());
exit (EXIT_FAILURE);
}
/* Read the size in bytes and print it. */
size = nbd_get_size (nbd);
if (size == -1) {
fprintf (stderr, "%s\n", nbd_get_error ());
exit (EXIT_FAILURE);
}
printf ("%s: size = %" PRIi64 " bytes\n",
argv[1], size);
/* Close the libnbd handle. */
nbd_close (nbd);
exit (EXIT_SUCCESS);
}
=head1 SEE ALSO
L<nbd_create(3)>,
L<nbd_opt_info(3)>,
L<libnbd(3)/Size of the export>,
L<libnbd(3)>,
L<nbdinfo(1)>.
=head1 AUTHORS
Eric Blake
Richard W.M. Jones
=head1 COPYRIGHT
Copyright Red Hat
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