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110 lines
3.0 KiB
110 lines
3.0 KiB
.. _how-to:
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******
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How To
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******
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Create a New Command Overlay
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============================
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:ref:`topics-overlays` are used to define the commands supported by a given application, service, or operating system. Commands are defined as a function.
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1) Define a Module
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------------------
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The first step is to create a new module in which functions will be defined.
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.. code-block:: python
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# module_name.py
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from ..commands import Command
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For overlays that represent an operating system, the ``command_exists()`` function is required:
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.. code-block:: python
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def command_exists(name):
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return name in MAPPINGS
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2) Define Command Function
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--------------------------
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The purpose of each function is to provide an interface for instantiating a :py:class`scripttease.library.commands.base.Command` instance. The example below is taken from the ``posix`` module.
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.. code-block:: python
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# module_name.py
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# ...
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def mkdir(path, mode=None, recursive=True, **kwargs):
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"""Create a directory.
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- path (str): The path to be created.
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- mode (int | str): The access permissions of the new directory.
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- recursive (bool): Create all directories along the path.
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"""
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kwargs.setdefault("comment", "create directory %s" % path)
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statement = ["mkdir"]
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if mode is not None:
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statement.append("-m %s" % mode)
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if recursive:
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statement.append("-p")
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statement.append(path)
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return Command(" ".join(statement), **kwargs)
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The arguments and any specific keyword arguments are automatically used by the parser, but also serve as a simple interface for programmatic use.
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Each function *must* also accept ``**kwargs`` and should set a default for ``comment`` as above.
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3) Add Functions to the Mapping
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-------------------------------
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The final step adds the function to the mapping. This makes it available to the command factory.
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.. code-block:: python
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# module_name.py
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# ...
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MAPPINGS = {
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'mkdir': mkdir,
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}
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For overlays that represent an operating system, ``MAPPINGS`` is required -- in addition to ``command_exists()`` above. For commands that are specific to service or application, the name of the dictionary may be anything that is appropriate. For example, ``DJANGO_MAPPINGS``.
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Additionally, for an operating system overlay, you may wish to import other mappings and incorporate them into ``MAPPINGS``.
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.. code-block:: python
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# module_name.py
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from ..commands import Command
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from .common import COMMON_MAPPINGS
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from .django import DJANGO_MAPPINGS
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from .pgsql import PGSQL_MAPPINGS
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MAPPINGS = {
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# ...
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}
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MAPPINGS.update(COMMON_MAPPINGS)
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MAPPINGS.update(DJANGO_MAPPINGS)
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MAPPINGS.update(PGSQL_MAPPINGS)
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Export Commands as a Script
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===========================
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.. code-block:: python
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config = Config("commands.ini")
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if not config.load():
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print("Bummer!")
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exit()
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script = config.as_script()
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print(script)
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