Startup Commands
================

``cmd2`` provides a couple different ways for running commands immediately
after your application starts up:

1. Commands at Invocation
2. Startup Script

Commands run as part of a startup script are always run immediately after the
application finishes initializing so they are guaranteed to run before any
*Commands At Invocation*.


Commands At Invocation
----------------------

.. _Argparse: https://docs.python.org/3/library/argparse.html

You can send commands to your app as you invoke it by including them as extra
arguments to the program. ``cmd2`` interprets each argument as a separate
command, so you should enclose each command in quotation marks if it is more
than a one-word command.  You can use either single or double quotes for this
purpose.

.. code-block:: shell

  $ python examples/example.py "say hello" "say Gracie" quit
  hello
  Gracie

You can end your commands with a **quit** command so that your ``cmd2``
application runs like a non-interactive command-line utility (CLU).  This
means that it can then be scripted from an external application and easily used
in automation.

.. note::

   If you wish to disable cmd2's consumption of command-line arguments, you can
   do so by setting the  ``allow_cli_args`` argument of your ``cmd2.Cmd`` class
   instance to ``False``.  This would be useful, for example, if you wish to
   use something like Argparse_ to parse the overall command line arguments for
   your application::

       from cmd2 import Cmd
       class App(Cmd):
           def __init__(self):
               super().__init__(allow_cli_args=False)


Startup Script
--------------

.. _AliasStartup: https://github.com/python-cmd2/cmd2/blob/master/examples/alias_startup.py

You can execute commands from an initialization script by passing a file
path to the ``startup_script`` argument to the ``cmd2.Cmd.__init__()`` method
like so::

    class StartupApp(cmd2.Cmd):
        def __init__(self):
            cmd2.Cmd.__init__(self, startup_script='.cmd2rc')

This text file should contain a :ref:`Command Script
<features/scripting:Command Scripts>`. See the AliasStartup_ example for a
demonstration.

You can silence a startup script's output by setting ``silence_startup_script``
to True::

    cmd2.Cmd.__init__(self, startup_script='.cmd2rc', silence_startup_script=True)

Anything written to stderr will still print. Additionally, a startup script
cannot be silenced if ``allow_redirection`` is False since silencing works
by redirecting a script's output to ``os.devnull``.