.\" Automatically generated by Podwrapper::Man 1.6.1 (Pod::Simple 3.40) .\" .\" Standard preamble: .\" ======================================================================== .de Sp \" Vertical space (when we can't use .PP) .if t .sp .5v .if n .sp .. .de Vb \" Begin verbatim text .ft CW .nf .ne \\$1 .. .de Ve \" End verbatim text .ft R .fi .. .\" Set up some character translations and predefined strings. \*(-- will .\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left .\" double quote, and \*(R" will give a right double quote. \*(C+ will .\" give a nicer C++. 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Of course, you'll have to process the .\" output yourself in some meaningful fashion. .\" .\" Avoid warning from groff about undefined register 'F'. .de IX .. .nr rF 0 .if \n(.g .if rF .nr rF 1 .if (\n(rF:(\n(.g==0)) \{\ . if \nF \{\ . de IX . tm Index:\\$1\t\\n%\t"\\$2" .. . if !\nF==2 \{\ . nr % 0 . nr F 2 . \} . \} .\} .rr rF .\" ======================================================================== .\" .IX Title "nbd_can_fast_zero 3" .TH nbd_can_fast_zero 3 "2021-02-09" "libnbd-1.6.1" "LIBNBD" .\" For nroff, turn off justification. Always turn off hyphenation; it makes .\" way too many mistakes in technical documents. .if n .ad l .nh .SH "NAME" nbd_can_fast_zero \- does the server support the fast zero flag? .SH "SYNOPSIS" .IX Header "SYNOPSIS" .Vb 1 \& #include \& \& int nbd_can_fast_zero (struct nbd_handle *h); .Ve .SH "DESCRIPTION" .IX Header "DESCRIPTION" Returns true if the server supports the use of the \&\f(CW\*(C`LIBNBD_CMD_FLAG_FAST_ZERO\*(C'\fR flag to the zero command (see \fBnbd_zero\fR\|(3), \fBnbd_aio_zero\fR\|(3)). Returns false if the server does not. .PP This call does not block, because it returns data that is saved in the handle from the \s-1NBD\s0 protocol handshake. .SH "RETURN VALUE" .IX Header "RETURN VALUE" This call returns a boolean value. .SH "ERRORS" .IX Header "ERRORS" On error \f(CW\*(C`\-1\*(C'\fR is returned. .PP Refer to \*(L"\s-1ERROR HANDLING\*(R"\s0 in \fBlibnbd\fR\|(3) for how to get further details of the error. .SH "HANDLE STATE" .IX Header "HANDLE STATE" The handle must be negotiating, or connected with the server, or shut down, otherwise this call will return an error. .SH "VERSION" .IX Header "VERSION" This function first appeared in libnbd 1.2. .PP If you need to test if this function is available at compile time check if the following macro is defined: .PP .Vb 1 \& #define LIBNBD_HAVE_NBD_CAN_FAST_ZERO 1 .Ve .SH "EXAMPLE" .IX Header "EXAMPLE" This example is also available as \fIexamples/server\-flags.c\fR in the libnbd source code. .PP .Vb 8 \& /* This example shows how to connect to an NBD \& * server and print the export flags. \& * \& * You can test it with nbdkit like this: \& * \& * nbdkit \-U \- memory 1M \e \& * \-\-run \*(Aq./server\-flags $unixsocket\*(Aq \& */ \& \& #include \& #include \& \& #include \& \& int \& main (int argc, char *argv[]) \& { \& struct nbd_handle *nbd; \& char *str; \& int flag; \& \& if (argc != 2) { \& fprintf (stderr, "%s socket\en", argv[0]); \& exit (EXIT_FAILURE); \& } \& \& /* Create the libnbd handle. */ \& nbd = nbd_create (); \& if (nbd == NULL) { \& fprintf (stderr, "%s\en", nbd_get_error ()); \& exit (EXIT_FAILURE); \& } \& \& /* Request full information. */ \& #if LIBNBD_HAVE_NBD_SET_FULL_INFO /* Added in 1.4 */ \& if (nbd_set_full_info (nbd, true) == \-1) { \& fprintf (stderr, "%s\en", nbd_get_error ()); \& exit (EXIT_FAILURE); \& } \& #endif \& \& /* Connect to the NBD server over a \& * Unix domain socket. \& */ \& if (nbd_connect_unix (nbd, argv[1]) == \-1) { \& fprintf (stderr, "%s\en", nbd_get_error ()); \& exit (EXIT_FAILURE); \& } \& \& /* See if the server provided extra details, \& * using functions added in 1.4 \& */ \& #if LIBNBD_HAVE_NBD_GET_EXPORT_DESCRIPTION \& str = nbd_get_canonical_export_name (nbd); \& if (str) \& printf ("canonical_name = %s\en", str); \& free (str); \& str = nbd_get_export_description (nbd); \& if (str) \& printf ("description = %s\en", str); \& free (str); \& #endif \& \& /* Read and print the flags. */ \& #define PRINT_FLAG(flag_fn) \e \& flag = flag_fn (nbd); \e \& if (flag == \-1) { \e \& fprintf (stderr, "%s\en", nbd_get_error ()); \e \& exit (EXIT_FAILURE); \e \& } \e \& printf (#flag_fn " = %s\en", \e \& flag ? "true" : "false"); \& \& PRINT_FLAG (nbd_can_cache); \& PRINT_FLAG (nbd_can_df); \& PRINT_FLAG (nbd_can_flush); \& PRINT_FLAG (nbd_can_fua); \& PRINT_FLAG (nbd_can_multi_conn); \& PRINT_FLAG (nbd_can_trim); \& PRINT_FLAG (nbd_can_zero); \& #if LIBNBD_HAVE_NBD_CAN_FAST_ZERO /* Added in 1.2 */ \& PRINT_FLAG (nbd_can_fast_zero); \& #endif \& PRINT_FLAG (nbd_is_read_only); \& PRINT_FLAG (nbd_is_rotational); \& \& /* Close the libnbd handle. */ \& nbd_close (nbd); \& \& exit (EXIT_SUCCESS); \& } .Ve .SH "SEE ALSO" .IX Header "SEE ALSO" \&\fBnbd_aio_zero\fR\|(3), \&\fBnbd_can_zero\fR\|(3), \&\fBnbd_create\fR\|(3), \&\fBnbd_opt_info\fR\|(3), \&\fBnbd_zero\fR\|(3), \&\*(L"Flag calls\*(R" in \fBlibnbd\fR\|(3), \&\fBlibnbd\fR\|(3). .SH "AUTHORS" .IX Header "AUTHORS" Eric Blake .PP Richard W.M. Jones .SH "COPYRIGHT" .IX Header "COPYRIGHT" Copyright (C) 2019\-2020 Red Hat Inc. .SH "LICENSE" .IX Header "LICENSE" This library is free software; you can redistribute it and/or modify it under the terms of the \s-1GNU\s0 Lesser General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. .PP This library is distributed in the hope that it will be useful, but \s-1WITHOUT ANY WARRANTY\s0; without even the implied warranty of \&\s-1MERCHANTABILITY\s0 or \s-1FITNESS FOR A PARTICULAR PURPOSE.\s0 See the \s-1GNU\s0 Lesser General Public License for more details. .PP You should have received a copy of the \s-1GNU\s0 Lesser General Public License along with this library; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, \s-1MA 02110\-1301 USA\s0