pyang

Name

pyang — validate and convert YANG modules to various formats

Synopsis

pyang [--canonical] [--ietf] [-o outfile] [-f format] [-p path] [-W what] module ...

pyang [ -h | --help ]

pyang [ -v | --version ]

Only the most common options are listed here. See below for a complete list of options.

Description

The pyang program is used to validate YANG modules. It is also used to convert YANG modules into equivalent YIN modules. From a valid module, a W3C XML Schema (XSD) or hybrid DSDL schema (RELAX NG with additional annotations) can be generated.

If no format is given, the specified modules are validated, and the program exits with exit code 0 if all modules are valid.

Options

-h --help

Print a short help text and exit.

-v --version

Print the version number and exit.

-e --list-errors

Print a listing of all error codes and messages pyang might generate, and then exit.

-Werror

Treat warnings as errors.

-Wnone

Do not print any warnings.

--canonical

Validate the module(s) according to the canonical YANG order.

--ietf

Validate the module(s) according to IETF rules as specified in draft-ietf-netmod-yang-usage. In addition, it checks that the module is in canonical order, and that --max-line-length is 72 so that the module fits into an RFC.

--max-line-length maxlen

Give a warning if any line is longer than maxlen.

--max-identifier-length maxlen

Give a error if any identifier is longer than maxlen.

-f --format format

Convert the module(s) into format. Some translators require a single module, and some can translate multiple modules at one time. If no outfile file is specified, the result is printed on stdout. The supported formats are listed in Output Formats below.

-o --output outfile

Write the output to the file outfile instead of stdout.

-p --path path

path is a colon (:) separated list of directories to search for imported modules. This option may be given multiple times.

The following directories are always added to the search path:

current directory
$YANG_MODPATH
$HOME/yang/modules
$YANG_INSTALL/yang/modules OR if $YANG_INSTALL is unset <the default installation directory>/yang/modules (on Unix systems: /usr/share/yang/modules)

--plugindir plugindir

Load all YANG plugins found in the directory plugindir. This option may be given multiple times.

list of directories to search for pyang plugins. The following directories are always added to the search path:

pyang/plugins from where pyang is installed
$PYANG_PLUGINPATH

module...

These are the names of the files containing the modules to be validated, or the module to be converted.

Output Formats

If pyang plugins are installed, these plugins may define their own options, or add new formats to the -f option. These options and formats are listed in pyang -h.

yin: the XML syntax of YANG
yang: normal YANG syntax
dsdl: Hybrid DSDL schema (RELAX NG with annotations)
xsd: W3C XML Schema
depend: Prints a Makefile dependency rule for the module
tree: tree structure of the module

YANG Output

Options for the yang output format:

--yang-canonical: Generate all statements in the canonical order.

YIN Output

Options for the yin output format:

--yin-canonical: Generate all statements in the canonical order.
--yin-pretty-strings: Pretty print strings, i.e. print with extra whitespace in the string. This is not strictly correct, since the whitespace is significant within the strings in XML, but the output is more readable.

DSDL Output

Options for the dsdl output format:

--dsdl-no-documentation: Do not print documentation annotations
--dsdl-no-dublin-core: Do not print Dublin Core metadata terms
--dsdl-record-defs: Record translations of all top-level typedefs and groupings in the output schema, even if they are not used. This is useful for translating library modules.

XSD Output

Options for the xsd output format:

--xsd-no-appinfo: Do not print YANG specific appinfo.
--xsd-no-lecture: Do not print the lecture about how the XSD can be used.
--xsd-no-imports: Do not generate any xs:imports.
--xsd-no-includes: Do not generate any xs:includes.
--xsd-break-pattern: Break long patterns so that they fit into RFCs. The resulting patterns might not always be valid XSD, so use with care.

Depend Output

The depend output generates a Makefile dependency rule for files based on a YANG module. This is useful if files are generated from the module. For example, suppose a .c file is generated from each YANG module. If the YANG module imports other modules, or includes submodules, the .c file needs to be regenerated if any of the imported or included modules change. Such a dependency rule can be generated like this:

$ pyang -f depend --depend-target mymod.c \
    --depend-extension .yang mymod.yang
mymod.c : ietf-yang-types.yang my-types.yang

Options for the depend output format:

--depend-target: Makefile rule target. Default is the modulename.
--depend-extension: YANG module file name extension. Default is no extension.
--depend-no-submodules: Do not generate dependencies for included submodules.

Tree Output

The tree output prints the resulting schema tree from one or more modules. Use pyang --tree-help to print a description on the symbols used by this format.

Tree output specific option:

--tree-help: Print help on symbols used in the tree output and exit.

Example

The following example validates the standard YANG modules with derived types:

$ pyang ietf-yang-types.yang ietf-inet-types.yang

The following example converts the ietf-yang-types module into YIN:

$ pyang -f yin -o ietf-yang-types.yin ietf-yang-types.yang

Environment Variables

pyang searches for referred modules in the colon (:) separated path defined by the environment variable $YANG_MODPATH and in the directory $YANG_INSTALL/yang/modules.

pyang searches for plugins in the colon (:) separated path defined by the environment variable $PYANG_PLUGINDIR.

BUGS

The XPath arguments for the must and when statements are checked only for basic syntax errors.
The translation of XPath expressions performed by the DSDL plugin doesn't add a prefix to local names that match the keyword of an XPath operator ("and", "or", "div", "mod") even if syntactically it cannot be such an operator. As a workaround, it is necessary to use an explicit prefix for these conflicting names in YANG.