Settings
Settings provide a mechanism for a user to control the behavior of a cmd2
based application. A setting is stored in an instance attribute on your subclass of cmd2.Cmd
and must also appear in the cmd2.Cmd.settable
dictionary. Developers may set default values for these settings and users can modify them at runtime using the set command. Developers can Create New Settings and can also Hide Builtin Settings from the user.
Builtin Settings
cmd2
has a number of builtin settings. These settings control the behavior of certain application features and Buildin Commands. Users can use the set command to show all settings and to modify the value of any setting.
allow_style
Output generated by cmd2
programs may contain ANSI escape sequences which instruct the terminal to apply colors or text styling (i.e. bold) to the output. The allow_style
setting controls the behavior of these escape sequences in output generated with any of the following methods:
cmd2.Cmd.poutput
cmd2.Cmd.perror
cmd2.Cmd.pwarning
cmd2.Cmd.pexcept
cmd2.Cmd.pfeedback
cmd2.Cmd.ppaged
This setting can be one of three values:
Never
- all ANSI escape sequences which instruct the terminal to style output are stripped from the output.Terminal
- (the default value) pass through ANSI escape sequences when the output is being sent to the terminal, but if the output is redirected to a pipe or a file the escape sequences are stripped.Always
- ANSI escape sequences are always passed through to the output
always_show_hint
If True
, display tab completion hint even when completion suggestions print. The default value of this setting is False
.
debug
The default value of this setting is False
, which causes the cmd2.Cmd.pexcept
method to only display the message from an exception. However, if the debug setting is True
, then the entire stack trace will be printed.
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. This behavior does not occur when running a command at the prompt.
editor
Similar to the EDITOR
shell variable, this setting contains the name of the program which should be run by the edit command.
feedback_to_output
Controls whether feedback generated with the cmd2.Cmd.pfeedback
method is sent to sys.stdout
or sys.stderr
. If False
the output will be sent to sys.stderr
If True
the output is sent to stdout
(which is often the screen but may be redirected). The feedback output will be mixed in with and indistinguishable from output generated with cmd2.Cmd.poutput
.
max_completion_items
Maximum number of CompletionItems to display during tab completion. A CompletionItem is a special kind of tab completion hint which displays both a value and description and uses one line for each hint. Tab complete the set
command for an example.
If the number of tab completion hints exceeds max_completion_items
, then they will be displayed in the typical columnized format and will not include the description text of the CompletionItem.
quiet
If True
, output generated by calling cmd2.Cmd.pfeedback
is suppressed. If False
, the feedback_to_output setting controls where the output is sent.
scripts_add_to_history
If True
, scripts and pyscripts add commands to history. The default value of this setting is True
.
timing
If True
, the elapsed time is reported for each command executed.
Create New Settings
Your application can define user-settable parameters which your code can reference. In your initialization code:
- Create an instance attribute with a default value
- Create a
Settable
object which describes your setting - Pass the
Settable
object tocmd2.Cmd.add_settable
Here's an example, from examples/environment.py:
If you want to be notified when a setting changes (as we do above), then be sure to supply a method to the onchange_cb
parameter of the cmd2.utils.Settable
. This method will be called after the user changes a setting, and will receive both the old value and the new value.
(Cmd) set | grep sunny
sunny False Is it sunny outside?
(Cmd) set | grep degrees
degrees_c 22 Temperature in Celsius
(Cmd) sunbathe
Too dim.
(Cmd) set degrees_c 41
degrees_c - was: 22
now: 41
(Cmd) set sunny
sunny: True
(Cmd) sunbathe
UV is bad for your skin.
(Cmd) set degrees_c 13
degrees_c - was: 41
now: 13
(Cmd) sunbathe
It's 13 C - are you a penguin?
Hide Builtin Settings
You may want to prevent a user from modifying a builtin setting. A setting must appear in the cmd2.Cmd.settable
dictionary in order for it to be available to the set command.
Let's say that you never want end users of your program to be able to enable full debug tracebacks to print out if an error occurs. You might want to hide the debug setting. To do so, remove it from the cmd2.Cmd.settable
dictionary after you initialize your object. The cmd2.Cmd.remove_settable
convenience method makes this easy: