# Application Cleanup

The concept of ‘cleanup’ after application run time is nothing new. What happens during ‘cleanup’ all depends on the application. This might mean closing and deleting temporary files, removing session data, or deleting a PID (Process ID) file.

To allow for application cleanup not only within your program, but also external plugins and extensions, there is the `app.close()` function that must be called after `app.run()` regardless of any exceptions or runtime errors.

For example:

    from cement.core.foundation import CementApp

    app = CementApp('helloworld')
    app.setup()
    app.run()
    app.close()

Calling `app.close()` ensures that the `pre_close` and `post_close` framework hooks are run, allowing extensions/plugins/etc to cleanup after the program runs.

Note that when using the Python `with` operator, the `setup()` and `close()` methods are automatically called. For example, the following is exactly the same as the above example:

    from cement.core.foundation import CementApp

    with CementApp('helloworld') as app:
        app.run()

Also note that you can optionally set an exit code to alter that status in which your application exits:

    app = CementApp('helloworld')
    app.setup()
    app.run()
    app.close(27)

Or Alternatively:

    with CementApp('helloworld') as app:
        app.run()
        app.exit_code = 123

The default exit code is `0`, however any uncaught exceptions will cause the application to exit with a code of `1` (error).

## Running Cleanup Code

Any extension, or plugin, or even the application itself that has ‘cleanup’ code should do so within the `pre_close` or `post_close` hooks to ensure that it gets run. For example:

    from cement.core import hook

    def my_cleanup(app):
        # do something when app.close() is called
        pass

    hook.register('pre_close', my_cleanup)