.. _source-code:

============
Code samples
============

Format code snippets as standalone literal blocks. There are several ways
to define a code-block within an RST file.

Standard literal block
~~~~~~~~~~~~~~~~~~~~~~

+------------------+---------------------------------------------------------+
| **Directive**    | ``::`` or ``code``                                      |
+------------------+---------------------------------------------------------+
| **Arguments**    | none                                                    |
+------------------+---------------------------------------------------------+
| **Options**      | none                                                    |
+------------------+---------------------------------------------------------+
| **Description**  | * Introduces a standard reST literal block.             |
|                  | * Preserves line breaks and whitespaces.                |
|                  | * Automatically highlights language (Python, by         |
|                  |   default)                                              |
+------------------+---------------------------------------------------------+

Use ``::`` or ``code`` directive if you provide the code snippets written
in one programming language within one file. By default, the code-block
formatted this way is shown in a Python highlighting mode.

To define another highlighting language, use the ``code-block`` directive
as described in the :ref:`non-standard-block` section. Make sure to close these
tags with ``end``. Additionally, add the ``path`` tag to provide the parser
with the path of the configuration files. This should allow the parser to parse
the markup syntax to Bash.

.. note::

  The ``end`` tag allows the parser to identify the scope of code blocks.
  The ``path`` tag allows the parser to identify the path of the config
  file. For more information, refer to the :doc:`rst2bash` section.
  These changes are mandatory only for the installation guides.

**Input**

.. code-block:: none

   Add logging statements::

     from nova.openstack.common import log as logging
     LOG = logging.getLogger(__name__)

**Output**

Add logging statements::

  from nova.openstack.common import log as logging
  LOG = logging.getLogger(__name__)

.. _non-standard-block:

Non-standard literal block
~~~~~~~~~~~~~~~~~~~~~~~~~~

+------------------+---------------------------------------------------------+
| **Directive**    | ``code-block``                                          |
+------------------+---------------------------------------------------------+
| **Arguments**    | ``python`` (default), ``ruby``, ``c``, ``console``,     |
|                  | ``ini``, and others                                     |
+------------------+---------------------------------------------------------+
| **Options**      | ``linenos``, ``emphasize-lines``                        |
+------------------+---------------------------------------------------------+
| **Description**  | * Specifies the highlighting language directly.         |
|                  | * Preserves line breaks and whitespaces.                |
+------------------+---------------------------------------------------------+

To optimize the output of code for a specific programming language, specify
the corresponding argument with ``code-block``. Use ``ini`` for configuration
files, ``console`` for console inputs and outputs, and so on.

**Input**

.. code-block:: rst

   .. path /path/to/config/file
   .. code-block:: ini

      # Configuration for nova-rootwrap
      # This file should be owned by (and only-writeable by) the root user

      [DEFAULT]
      # List of directories to load filter definitions from (separated by ',').

**Output**

.. code-block:: ini

   # Configuration for nova-rootwrap
   # This file should be owned by (and only-writeable by) the root user

   [DEFAULT]
   # List of directories to load filter definitions from (separated by ',').

.. note::

   When you write the command example, you should write the input and output
   as it is from the console in one code block, not add an extra blank line,
   not split them into input block and output block.
   You can omit the output where appropriate.

Options of code-block directive
-------------------------------

You can add line numbers to code examples with the ``:linenos:`` parameter and
highlight some specific lines with the ``:emphasize-lines:`` parameter:

**Input**

.. code-block:: rst

   .. code-block:: python
      :linenos:
      :emphasize-lines: 3,5-6

      def some_function():
          interesting = False
          print 'This line is highlighted.'
          print 'This one is not...'
          print '...but this one is.'
          print 'This one is highlighted too.'

**Output**

.. code-block:: python
   :linenos:
   :emphasize-lines: 3,5-6

   def some_function():
       interesting = False
       print 'This line is highlighted.'
       print 'This one is not...'
       print '...but this one is.'
       print 'This one is highlighted too.'

.. _remote-block:

Literal block using a remote file
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

+-----------------+-----------------------------------------------------+
| **Directive**   | ``remote-code-block``                               |
+-----------------+-----------------------------------------------------+
| **Arguments**   | ``python`` (default), ``ruby``, ``c``, ``console``, |
|                 | ``ini``, and others                                 |
+-----------------+-----------------------------------------------------+
| **Options**     | ``linenos``, ``emphasize-lines``                    |
+-----------------+-----------------------------------------------------+
| **Description** | * Specifies the highlighting language directly.     |
|                 | * Preserves line breaks and whitespaces.            |
+-----------------+-----------------------------------------------------+

This directive behaves exactly like the ``code-block`` directive, but gets the
content from a remote URL (``http`` or ``https``).

``remote-code-block`` is a custom directive.

**Input**

.. code-block:: rst

   .. path /path/to/config/file
   .. remote-code-block:: ini

      https://git.openstack.org/cgit/openstack/nova/tree/etc/nova/api-paste.ini?h=stable/ocata

**Output**

.. code-block:: yaml

   ############
   # Metadata #
   ############
   [composite:metadata]
   use = egg:Paste#urlmap
   /: meta

   [pipeline:meta]
   pipeline = cors ec2faultwrap logrequest metaapp