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