# libnm Reference Manual

for libnm &version; The latest version of this documentation can be found on-line at https://developer.gnome.org/libnm/stable/.
2012 2013 2014 2015 2016 2017 The NetworkManager Authors

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## Overview

### Introduction to libnm

libnm is a client library for NetworkManager, the standard Linux network management service. NetworkManager supports a wide variety of network configuration scenarios, hardware devices and protocol families. Most of the functionality is exposed on a D-Bus API, allowing other tools to use the functionality provided by NetworkManager.

libnm provides C language bindings for functionality provided by NetworkManager, optionally useful from other language runtimes as well.

libnm maps fairly closely to the actual D-Bus API that NetworkManager provides, wrapping the remote D-Bus objects as native GObjects, mapping D-Bus signals and properties to GObject signals and properties, and providing helpful accessor and utility functions. However, unlike the old libnm-util/libnm-glib API, the mapping to the D-Bus API is not exact, and various inconveniences and historical anomolies of the D-Bus API are papered over.

The following is a rough overview of the libnm object structure and how to use the various parts of it:

### Using libnm

#### When to use libnm

libnm is fairly simple to use from C. It's based on glib and GObject. If your project uses these already you'll find integration libnm with your project rather convenient. In fact, the `nmcli` tool shipped with NetworkManager is based on libnm.

libnm should be also the way to go if your project does something non-trivial with NetworkManager, such as manipulating the connection profiles. That is, if you're writing a specialized networking control tool or a desktop environment, libnm is probably the right choice. The popular desktop environments in fact all use libnm directly or with nm-applet and nm-connection-editor that are all based on libnm.

An alternative to use of libnm is the use of the D-Bus API directly. This gives you larger flexibility and reduces the overhead of linking with the libnm library. This makes sense if your task is simple and you have a good D-Bus library at your disposal. Activating a particular connection profile from a Python script is a good example of a task that is perfectly simple without using libnm.

#### How to use libnm

You can use the libnm's C API directly. To do so, all libnm programs need to include `NetworkManager.h` that provides necessary definitions. The rest of the API is documented in the reference manual.

    #include <glib.h>
    #include <NetworkManager.h>

    int
    main (int argc, char *argv[])
    {
    	NMClient *client;

    	client = nm_client_new (NULL, NULL);
    	if (client)
    		g_print ("NetworkManager version: %s\n", nm_client_get_version (client));
    }

Use `pkg-config` for `libnm` to discover the necessary compiler flags.

    $ cc $(pkg-config --libs --cflags libnm) -o hello-nm hello-nm.c
      $ ./hello-nm
      NetworkManager version: &version;
      $

Utilize the `PKG_CHECK_MODULES` macro to integrate with an autoconf-based build system. It's also recommended to use `NM_VERSION_MIN_REQUIRED` and `NM_VERSION_MAX_ALLOWED` macros to tell libnm headers which API version does your application need to work with. If you use them, the compiler will warn you when you use functionality that is not available in the versions you specified.

    PKG_CHECK_MODULES(LIBNM, libnm >= 1.8)
    LIBNM_CFLAGS="$LIBNM_CFLAGS -DNM_VERSION_MIN_REQUIRED=NM_VERSION_1_8"
    LIBNM_CFLAGS="$LIBNM_CFLAGS -DNM_VERSION_MAX_ALLOWED=NM_VERSION_1_8"

You can use libnm from other languages than C with the use of GObject introspection. This includes Perl, Python, Javascript, Lua, Ruby and more. The example below shows what the typical libnm use in Python would look like.

    import gi
    gi.require_version('NM', '1.0')
    from gi.repository import NM

    client = NM.Client.new(None)
    print ("NetworkManager version " + client.get_version())

There's NM-1.0 Python API Reference maintained a third party that is generated from the introspection metadata.

In general, the C API documentation applies to the use GObject introspection from other languages, with the calling convention respecting the language's customs. Consult the source tree for some examples.

## Client Object API Reference

## Connection and Setting API Reference

## Device and Runtime Configuration API Reference

## Utility API Reference

## VPN Plugin API Reference

## Object Hierarchy

API Index