libyang

libyang is YANG data modelling language parser and toolkit written (and providing API) in C.

Provided Features

• Parsing (and validating) schemas in YANG format.
• Parsing (and validating) schemas in YIN format.
• Parsing, validating and printing instance data in XML format.
• Parsing, validating and printing instance data in JSON format.
• Manipulation with the instance data.
• Support for adding default values into instance data.

Current implementation covers YANG 1.0 specified by RFC 6020.

Planned Features

• YANG 1.1 support.

Requirements

• cmake >= 2.6
• libpcre
• cmocka >= 1.0.0 (for tests only, see Tests)

Building

$ mkdir build; cd build
$ cmake ..
$ make 
# make install

Documentation

The library documentation can be generated directly from the source codes using Doxygen tool:

$ make doc
$ google-chrome ../doc/html/index.html

Useful CMake Options

Changing Compiler

Set CC variable:

$ CC=/usr/bin/clang cmake ..

Changing Install Path

To change the prefix where the library, headers and any other files are installed, set CMAKE_INSTALL_PREFIX variable:

$ cmake -DCMAKE_INSTALL_PREFIX:PATH=/usr ..

Default prefix is /usr/local.

Build Modes

There are two build modes:

• Release. This generates library for the production use without any debug information.
• Debug. This generates library with the debug information and disables optimization of the code.

The Debug mode is currently used as the default one. to switch to the Release mode, enter at the command line:

$ cmake -D CMAKE_BUILD_TYPE:String="Release" ..

CMake Notes

Note that, with CMake, if you want to change the compiler or its options after you already ran CMake, you need to clear its cache first - the most simple way to do it is to remove all content from the 'build' directory.

Usage

All libyang functions are available via the main header:

#include <libyang/libyang.h>

To compile your program with libyang, it is necessary to link it with libyang using the following linker parameters:

-lyang

Note, that it may be necessary to call ldconfig(8) after library installation and if the library was installed into a non-standard path, the path to libyang must be specified to the linker. To help with setting all the compiler's options, there is libyang.pc file for pkg-config(1) available in the source tree. The file is installed with the library.

If you are using cmake in you project, it is also possible to use the provided FindLibYANG.cmake file to detect presence of the libyang library in the system.

Tests

libyang includes several tests built with cmocka. The tests can be found in tests subdirectory and they are designed for checking library functionality after code changes.

The tests are by default built in the Debug build mode by running

$ make

In case of the Release mode, the tests are not built by default (it requires additional dependency), but it can be enabled via cmake option:

$ cmake -DENABLE_BUILD_TESTS=ON ..

Note that if the necessary cmocka headers are not present in the system include paths, tests are not available despite the build mode or cmake's options.

Tests can be run by the make's test target:

$ make test

Bindings

We provide bindings for high-level languages using SWIG generator. The bindings are optional and to enable building of the specific binding, the appropriate cmake option must be enabled, for example:

$ cmake -DJAVASCRIPT_BINDING=ON ..

More information about the specific binding can be found in their README files.

Currently supported bindings are:

• JavaScript
• cmake option: JAVASCRIPT_BINDING
• README

yanglint

libyang source codes include a simple example tool to demanstrate how an application can work with the libyang library. The tool is called yanglint. It is not being installed together with the library itself, but it is built together with the library binary and you can find it in tools/lint directory.

There is also README describing some examples of using yanglint.