=encoding utf8

=head1 NAME

guestfs-lua - How to use libguestfs from Lua

=head1 SYNOPSIS

 local G = require "guestfs"
 g = G.create ()
 g:add_drive ("test.img", { format = "raw", readonly = true })
 g:launch ()
 devices = g:list_devices ()
 g:close ()

=head1 DESCRIPTION

This manual page documents how to call libguestfs from the Lua
programming language.  This page just documents the differences from
the C API and gives some examples.  If you are not familiar with using
libguestfs, you also need to read L<guestfs(3)>.

=head2 REQUIRING THE MODULE

C<require "guestfs"> returns the module, so you have to assign it
to a local variable.  Typical usage is:

 local G = require "guestfs"

(you can use any name you want instead of C<G>, but in the examples
in this man page we always use C<G>).

=head2 OPENING AND CLOSING THE HANDLE

To create a new handle, call:

 g = G.create ()

You can also use the optional arguments:

 g = G.create { environment = 0, close_on_exit = 0 }

to set the flags C<GUESTFS_CREATE_NO_ENVIRONMENT>
and/or C<GUESTFS_CREATE_NO_CLOSE_ON_EXIT>.

The handle will be closed by the garbage collector, but you can
also close it explicitly by doing:

 g:close ()

=head2 CALLING METHODS

Use the ordinary Lua convention for calling methods on the handle.
For example:

 g:set_verbose (true)

=head2 FUNCTIONS WITH OPTIONAL ARGUMENTS

For functions that take optional arguments, the first arguments are
the non-optional ones.  The optional final argument is a table
supplying the optional arguments.

 g:add_drive ("test.img")

or:

 g:add_drive ("test.img", { format = "raw", readonly = true })

=head2 64 BIT VALUES

Currently 64 bit values must be passed as strings, and are returned as
strings.  This is because 32 bit Lua cannot handle 64 bit integers
properly.  We hope to come up with a better solution later.

=head2 ERRORS

Most (but not all) errors are converted into objects (ie. tables)
containing the following fields:

=over 4

=item msg

The error message (corresponding to L<guestfs(3)/guestfs_last_error>).

=item code

The C<errno> (corresponding to L<guestfs(3)/guestfs_last_errno>).

=back

These objects also have C<__tostring> functions attached to them
so you can use C<tostring> (or implicit conversion) to convert them
into printable strings.

Note that the library also throws some errors as plain strings.  You
may need to check the type.

=head2 EVENTS

Events can be registered by calling C<set_event_callback>:

 eh = g:set_event_callback (cb, "close")

or to register a single callback for multiple events make the
second argument a list:

 eh = g:set_event_callback (cb, { "appliance", "library", "trace" })

A list of all valid event types (strings) is in the global variable
C<G.event_all>.

The callback (C<cb>) is called with the following parameters:

 function cb (g, event, eh, flags, buf, array)
   -- g is the guestfs handle
   -- event is a string which is the name of the event that fired
   -- flags is always zero
   -- buf is the data buffer (eg. log message etc)
   -- array is the array of 64 bit ints (eg. progress bar status etc)
   ...
 end

You can also remove a callback using the event handle (C<eh>) that was
returned when you registered the callback:

 g:delete_event_callback (eh)

=head1 EXAMPLE 1: CREATE A DISK IMAGE

@EXAMPLE1@

=head1 EXAMPLE 2: INSPECT A VIRTUAL MACHINE DISK IMAGE

@EXAMPLE2@

=head1 SEE ALSO

L<guestfs(3)>,
L<guestfs-examples(3)>,
L<guestfs-erlang(3)>,
L<guestfs-java(3)>,
L<guestfs-ocaml(3)>,
L<guestfs-perl(3)>,
L<guestfs-python(3)>,
L<guestfs-recipes(1)>,
L<guestfs-ruby(3)>,
L<http://www.lua.org/>,
L<http://libguestfs.org/>.

=head1 AUTHORS

Richard W.M. Jones (C<rjones at redhat dot com>)

=head1 COPYRIGHT

Copyright (C) 2012 Red Hat Inc.