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.\"
.IX Title "libnbd-ocaml 3"
.TH libnbd-ocaml 3 2024-05-31 libnbd-1.20.0 LIBNBD
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
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.SH NAME
libnbd\-ocaml \- how to use libnbd from OCaml
.SH SYNOPSIS
.IX Header "SYNOPSIS"
.Vb 5
\& let nbd = NBD.create () in
\& NBD.connect_uri nbd "nbd://localhost";
\& let size = NBD.get_size nbd in
\& printf "%Ld\en" size;
\& NBD.close ()
.Ve
.PP
Alternate syntax which ensures that close is called even if an
exception is thrown:
.PP
.Vb 7
\& let size =
\&   NBD.with_handle (
\&     fun nbd \->
\&       NBD.connect_uri nbd "nbd://localhost";
\&       NBD.get_size nbd
\&   ) in
\& printf "%Ld\en" size
.Ve
.PP
To compile:
.PP
.Vb 1
\& ocamlopt \-I +nbd mlnbd.cmxa prog.ml \-o prog
.Ve
.PP
or using findlib:
.PP
.Vb 1
\& ocamlfind opt \-package nbd \-linkpkg prog.ml \-o prog
.Ve
.SH DESCRIPTION
.IX Header "DESCRIPTION"
This manual page documents how to use libnbd to access Network Block
Device (NBD) servers from the OCaml programming language.
.PP
The OCaml bindings work very similarly to the C bindings so you should
start by reading \fBlibnbd\fR\|(3).
.PP
For OCaml API documentation see \fBNBD\fR\|(3).
.SH HANDLES
.IX Header "HANDLES"
Create a libnbd handle of type \f(CW\*(C`NBD.t\*(C'\fR by calling \f(CW\*(C`NBD.create\ ()\*(C'\fR.
.PP
You can either close the handle explicitly by calling \f(CW\*(C`NBD.close\*(C'\fR or
it will be closed automatically when it is garbage collected.  If you
call any other method on a handle which you have explicitly closed
then the API will throw an \f(CW\*(C`NBD.Closed\*(C'\fR exception.
.PP
\&\f(CW\*(C`NBD.with_handle\*(C'\fR can be used to make sure the handle is closed in a
timely manner.  See the example in the "SYNOPSIS" above.
.SH ERRORS
.IX Header "ERRORS"
Libnbd errors are turned automatically into exceptions of type:
.PP
.Vb 1
\& NBD.Error (str, Unix.error option)
.Ve
.PP
The first exception parameter is a string which is the printable error
message.  The second is the OCaml \f(CW\*(C`Unix.error\*(C'\fR code, if available
(see \fBnbd_get_errno\fR\|(3)).
.SS "Callbacks with ""int ref"" error parameter"
.IX Subsection "Callbacks with ""int ref"" error parameter"
Some callbacks take an error parameter of type \f(CW\*(C`int ref\*(C'\fR,
corresponding to the \f(CW\*(C`int *error\*(C'\fR passed to those callbacks in C.
See also: "Callbacks with "int *error" parameter" in \fBlibnbd\fR\|(3)
.PP
If an error occurs during the callback you can update the \f(CW\*(C`int\*(C'\fR in
the reference, setting it to a \fIC\-compatible errno\fR.  To convert an
OCaml \f(CW\*(C`Unix.error\*(C'\fR into a C\-compatible errno call
\&\f(CW\*(C`NBD.errno_of_unix_error\*(C'\fR.
.SH EXAMPLES
.IX Header "EXAMPLES"
This directory contains examples written in OCaml:
.PP
https://gitlab.com/nbdkit/libnbd/tree/master/ocaml/examples
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBlibnbd\fR\|(3), \fBNBD\fR\|(3).
.SH AUTHORS
.IX Header "AUTHORS"
Richard W.M. Jones
.SH COPYRIGHT
.IX Header "COPYRIGHT"
Copyright Red Hat
.SH LICENSE
.IX Header "LICENSE"
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU 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 WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
Lesser General Public License for more details.
.PP
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110\-1301 USA