libyang is a YANG data modelling language parser and toolkit written (and providing API) in C. The library is used e.g. in libnetconf2, Netopeer2 or sysrepo projects.
The project uses 2 main branches master and devel. Other branches should not be cloned. In master there are files of the
last official release. Any latest improvements and changes, which were tested at least briefly are found in devel. On every
new release, devel is merged into master.
This means that when only stable official releases are to be used, either master can be used or specific releases downloaded.
If all the latest bugfixes should be applied, devel branch is the one to be used. Note that whenever a new issue is created
and it occurs on the master branch, the first response will likely be to use devel before any further provided support.
Look into the documentation and the section Transition Manual. That should help with basic migration and the
ability to compile a project. But to actually make use of the new features, it is required to read through
the whole documentation and the API.
- 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 (RFC 7951).
- Manipulation with the instance data.
- Support for default values in the instance data (RFC 6243).
- Support for YANG extensions.
- Support for YANG Metadata (RFC 7952).
- Support for YANG Schema Mount (RFC 8528).
- Support for YANG Structure (RFC 8791).
- yanglint - feature-rich YANG tool.
Current implementation covers YANG 1.0 (RFC 6020) as well as YANG 1.1 (RFC 7950).
Binary RPM or DEB packages of the latest release can be built locally using apkg, look into README in
the distro directory.
- C compiler
- cmake >= 2.8.12
- libpcre2 >= 10.21 (including devel package)
- xxhash (for faster hashing)
- doxygen (for generating documentation)
- cmocka >= 1.0.1 (for tests)
- valgrind (for enhanced testing)
- gcov (for code coverage)
- lcov (for code coverage)
- genhtml (for code coverage)
- libpcre2 >= 10.21
- Visual Studio 17 (2022)
- cmake >= 3.22.0
- libpcre2 (same considerations as on POSIX)
pthreads-win32direntdlfcn-win32getopt-win32
The Windows version does not support plugins, and the yanglint works in a non-interactive mode only.
On Windows, all YANG date-and-time values are first converted to UTC (if TZ offset was specified), and then returned with "unspecified timezone".
$ mkdir build; cd build
$ cmake ..
$ make
# make install
Set CC variable:
$ CC=/usr/bin/clang cmake ..
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.
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" ..
As for YANG extensions, libyang allows loading extension plugins. By default, the directory to store the plugins is LIBDIR/libyang. To change it, use the following cmake option with the value specifying the desired directory:
$ cmake -DPLUGINS_DIR:PATH=`pwd`"/src/extensions/" ..
The directory path can be also changed runtime via environment variable, e.g.:
$ LIBYANG_EXTENSIONS_PLUGINS_DIR=`pwd`/my/relative/path yanglint
Note that plugins are not available on Windows.
Whenever the latest revision of a schema is supposed to be loaded (import without specific revision), it is performed in the standard way, the first time. By default, every other time when the latest revision of the same schema is needed, the one initially loaded is reused. If you know this can cause problems meaning the latest available revision of a schema can change during operation, you can force libyang to always search for the schema anew by:
$ cmake -DENABLE_LATEST_REVISIONS=OFF ..
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.
All libyang functions are available via the main header:
#include <libyang/libyang.h>