Features requiring only parameter changes

Several aspects of a cmd2 application’s behavior can be controlled simply by setting attributes of App. A parameter can also be changed at runtime by the user if its name is included in the dictionary app.settable. (To define your own user-settable parameters, see Other user-settable parameters)

Shortcuts

Command shortcuts for long command names and common commands can make life more convenient for your users. Shortcuts are used without a space separating them from their arguments, like !ls. By default, the following shortcuts are defined:

?
help
!
shell: run as OS-level command
@
run script file
@@
run script file; filename is relative to current script location

To define more shortcuts, update the dict App.shortcuts with the {‘shortcut’: ‘command_name’} (omit do_):

class App(Cmd2):
    def __init__(self):
      shortcuts = dict(self.DEFAULT_SHORTCUTS)
      shortcuts.update({'*': 'sneeze', '~': 'squirm'})
      cmd2.Cmd.__init__(self, shortcuts=shortcuts)

Warning

Shortcuts need to be created by updating the shortcuts dictionary attribute prior to calling the cmd2.Cmd super class __init__() method. Moreover, that super class init method needs to be called after updating the shortcuts attribute This warning applies in general to many other attributes which are not settable at runtime.

Aliases

In addition to shortcuts, cmd2 provides a full alias feature via the alias command. Aliases work in a similar fashion to aliases in the Bash shell.

The syntax to create an alias is: alias create name command [args].

Ex: alias create ls !ls -lF

For more details run: help alias create

Use alias list to see all or some of your aliases. The output of this command displays your aliases using the same command that was used to create them. Therefore you can place this output in a cmd2 startup script to recreate your aliases each time you start the application

Ex: alias list

For more details run: help alias list

Use alias delete to remove aliases

For more details run: help alias delete

Macros

cmd2 provides a feature that is similar to aliases called macros. The major difference between macros and aliases is that macros can contain argument placeholders. Arguments are expressed when creating a macro using {#} notation where {1} means the first argument.

The following creates a macro called my_macro that expects two arguments:

macro create my_macro make_dinner -meat {1} -veggie {2}

When the macro is called, the provided arguments are resolved and the assembled command is run. For example:

my_macro beef broccoli —> make_dinner -meat beef -veggie broccoli

For more details run: help macro create

The macro command has list and delete subcommands that function identically to the alias subcommands of the same name. Like aliases, macros can be created via a cmd2 startup script to preserve them across application sessions.

For more details on listing macros run: help macro list

For more details on deleting macros run: help macro delete

Default to shell

Every cmd2 application can execute operating-system level (shell) commands with shell or a ! shortcut:

(Cmd) shell which python
/usr/bin/python
(Cmd) !which python
/usr/bin/python

However, if the parameter default_to_shell is True, then every command will be attempted on the operating system. Only if that attempt fails (i.e., produces a nonzero return value) will the application’s own default method be called.

(Cmd) which python
/usr/bin/python
(Cmd) my dog has fleas
sh: my: not found
*** Unknown syntax: my dog has fleas

Quit on SIGINT

On many shells, SIGINT (most often triggered by the user pressing Ctrl+C) only cancels the current line, not the entire command loop. By default, a cmd2 application will quit on receiving this signal. However, if quit_on_sigint is set to False, then the current line will simply be cancelled.

(Cmd) typing a comma^C
(Cmd)

Warning

The default SIGINT behavior will only function properly if cmdloop is running in the main thread.

Timing

Setting App.timing to True outputs timing data after every application command is executed. The user can set this parameter during application execution. (See Other user-settable parameters)

Echo

If True, each command the user issues will be repeated to the screen before it is executed. This is particularly useful when running scripts.

Debug

Setting App.debug to True will produce detailed error stacks whenever the application generates an error. The user can set this parameter during application execution. (See Other user-settable parameters)

Other user-settable parameters

A list of all user-settable parameters, with brief comments, is viewable from within a running application with:

(Cmd) set --long
colors: Terminal               # Allow colorized output
continuation_prompt: >         # On 2nd+ line of input
debug: False                   # Show full error stack on error
echo: False                    # Echo command issued into output
editor: vim                    # Program used by ``edit``
feedback_to_output: False      # include nonessentials in `|`, `>` results
locals_in_py: False            # Allow access to your application in py via self
prompt: (Cmd)                  # The prompt issued to solicit input
quiet: False                   # Don't print nonessential feedback
timing: False                  # Report execution times

Any of these user-settable parameters can be set while running your app with the set command like so:

set colors Never