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

@

load script file

@@

load 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):
      # Make sure you update the shortcuts attribute before calling the super class __init__
      self.shortcuts.update({'*': 'sneeze', '~': 'squirm'})

      # Make sure to call this super class __init__ after updating shortcuts
      cmd2.Cmd.__init__(self)

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 such as commentGrammars, multilineCommands, etc.

Aliases¶

In addition to shortcuts, cmd2 provides a full alias feature via the alias command which is similar to the alias command in Bash.

The syntax to create an alias is alias <name> <value>. value can contain spaces and does not need to be quoted. Ex: alias ls !ls -lF

If alias is run without arguments, then a list of all aliases will be printed to stdout and are in the proper alias command syntax, meaning they can easily be reused.

The unalias is used to clear aliases. Using the -a flag will clear all aliases. Otherwise provide a list of aliases to clear. Ex: unalias ls cd pwd will clear the aliases called ls, cd, and pwd.

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)

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: True                   # Colorized output (*nix only)
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: True             # 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 False