cmd2 Application Lifecycle and Hooks¶
The typical way of starting a cmd2 application is as follows:
from cmd2 import Cmd class App(Cmd): # customized attributes and methods here app = App() app.cmdloop()
There are several pre-existing methods and attributes which you can tweak to control the overall behavior of your application before, during, and after the main loop.
Application Lifecycle Hook Methods¶
postloop methods run before and after the main loop, respectively.
Application Lifecycle Attributes¶
There are numerous attributes (member variables of the
cmd2.Cmd) which have a significant effect on the application
behavior upon entering or during the main loop. A partial list of some of the more important ones is presented here:
- intro: str - if provided this serves as the intro banner printed once at start of application, after
- allow_cli_args: bool - if True (default), then searches for -t or –test at command line to invoke transcript testing mode instead of a normal main loop
- and also processes any commands provided as arguments on the command line just prior to entering the main loop
- echo: bool - if True, then the command line entered is echoed to the screen (most useful when running scripts)
- prompt: str - sets the prompt which is displayed, can be dynamically changed based on application state and/or
- command results
Command Processing Hooks¶
Inside the main loop, every time the user hits <Enter> the line is processed by the
onecmd_plus_hooks name implies, there are a number of hook methods that can be defined in order to inject
application-specific behavior at various points during the processing of a line of text entered by the user.
increases the 2 hooks provided by
cmd (precmd and postcmd) to 6 for greater flexibility. Here are
the various hook methods, presented in chronological order starting with the ones called earliest in the process.