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 features/builtin_commands:set
command. Developers can features/settings:Create New Settings
and can also features/settings:Hide Builtin Settings
from the user.
cmd2
has a number of builtin settings. These settings control the behavior of certain application features and features/builtin_commands:Builtin
Commands
. Users can use the features/builtin_commands:set
command to show all settings and to modify the value of any setting.
Output generated by cmd2
programs may contain ANSI escape seqences 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
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.
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.
Similar to the EDITOR
shell variable, this setting contains the name of the program which should be run by the features/builtin_commands:edit
command.
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 <features/redirection:Output Redirection and Pipes>
). The feedback output will be mixed in with and indistinguishable from output generated with ~cmd2.Cmd.poutput
.
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.
If True
, output generated by calling ~cmd2.Cmd.pfeedback
is suppressed. If False
, the features/settings:feedback_to_output
setting controls where the output is sent.
If True
, the elapsed time is reported for each command executed.
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
:
../../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 --long | grep sunny
sunny: False # Is it sunny outside?
(Cmd) set --long | 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?
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 features/builtin_commands: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 features/settings: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:
class MyApp(cmd2.Cmd):
def __init__(self):
super().__init__()
self.remove_settable('debug')