nut/docs/new-clients.txt

Creating new client
===================

NUT provides bindings for several common languages that are
presented below. All these are released under the same license as
NUT (the GNU General Public License).

If none of these suits you for technical or legal reasons, you can
implement one easily using the <<net-protocol,Network protocol information>>.

The latter approach has been used to create the Python 'PyNUT' module, the
Nagios 'check_ups' plugin (and probably others), which can serve as a
reference.

C / C++
-------

Client access library
~~~~~~~~~~~~~~~~~~~~~

The upsclient library can be linked into other programs to give access
to upsd and UPS status information. Both static and shared versions are provided.

Clients like upsc are provided as examples of how to retrieve data using the
upsclient functions.
link:http://www.networkupstools.org/projects.html[Other programs] not included
in this package may also use this library, such as wmnut.

This library file and the associated header files are not installed by
default.  You must `./configure --with-lib` to enable building and
installing these files. The libraries can then be built and installed
with `make` and `make install` as usual. This must be done before
building other (non-NUT) programs which depend on them.

For more information, refer to the linkman:upsclient[3],
manual page and the various
link:man/index.html#Developer_man[upscli_*(3)] functions documentation
referenced in the same file.

Configuration helpers
~~~~~~~~~~~~~~~~~~~~~

NUT provides helper scripts to ease the configuration step of your program, by
detecting the right compilation and link flags:

- one for platforms providing pkg-config,
- and the other (libupsclient-config) for platforms not providing pkg-config.

If you have pkg-config installed, and you need to find the location of the NUT
client include files, add the output of the following command to your build
system (which can be combined with other pkg-config invocations):

   pkg-config libupsclient --cflags

If you don't have pkg-config, use this:

   libupsclient-config --cflags

Reference: linkman:libupsclient-config[1]

Python
------

The PyNUT module, contributed by David Goncalves, can be used for connecting a
Python script to `upsd`. Note that this code (and the accompanying NUT-Monitor
application) is licensed under the GPL v3.

The `PyNUTClient` class abstracts the connection to the server. In order to
list the status variables for `ups1` on the local `upsd`, the following
commands could be used:

  $ cd scripts/python/module
  $ python
  ...
  >>> import PyNUT
  >>> from pprint import pprint
  >>> client = PyNUT.PyNUTClient()
  >>> vars = client.GetUPSVars('ups1')
  >>> pprint(vars)
  {'battery.charge': '90',
   'battery.charge.low': '30',
   'battery.runtime': '3690',
   'battery.voltage': '230.0',
  ...

Further examples are given in the `test_nutclient.py` file. To see the entire
API, you can run `pydoc` from the `module` directory.

If you wish to make the module available to everyone on the system, you will
probably want to install it in the `site-packages` directory for your Python
interpreter. (This is usually one of the last items in `sys.path`.)

Perl
----

The old Perl bindings from CPAN have recently been updated and merged into the
NUT source code. These operate in a similar fashion to the Python bindings,
with the addition of access to single variables, and additional interpretation
of the results. The Perl class instance encapsulates a single UPS, where the
Python class instance represents a connection to the server (which may service
multiple UPS units).

 use UPS::Nut;

 $ups = new UPS::Nut( NAME => "myups",
                      HOST => "somemachine.somewhere.com",
                      PORT => "3493",
                      USERNAME => "upsuser",
                      PASSWORD => "upspasswd",
                      TIMEOUT => 30,
                      DEBUG => 1,
                      DEBUGOUT => "/some/file/somewhere",
                    );
 if ($ups->Status() =~ /OB/) {
    print "Oh, no!  Power failure!\n";
 }

 tie %other_ups, 'UPS::Nut',
     NAME => "myups",
     HOST => "somemachine.somewhere.com",
     ... # same options as new();
 ;

 print $other_ups{MFR}, " ", $other_ups{MODEL}, "\n";