This document has useful information for developers wishing to write new
The QMK CLI operates using the subcommand pattern made famous by git. The main
qmk script is simply there to setup the environment and pick the correct entrypoint to run. Each subcommand is a self-contained module with an entrypoint (decorated by
@cli.subcommand()) that performs some action and returns a shell returncode, or None.
MILC is the CLI framework
qmk uses to handle argument parsing, configuration, logging, and many other features. It lets you focus on writing your tool without wasting your time writing glue code.
Subcommands in the local CLI are always found in
Let's start by looking at an example subcommand. This is
"""QMK Python Hello WorldThis is an example QMK CLI script."""from milc import firstname.lastname@example.org('-n', '--name', default='World', help='Name to greet.')@cli.subcommand('QMK Hello World.')def hello(cli):"""Log a friendly greeting."""cli.log.info('Hello, %s!', cli.config.hello.name)
First we import the
cli object from
milc. This is how we interact with the user and control the script's behavior. We use
@cli.argument() to define a command line flag,
--name. This also creates a configuration variable named
hello.name (and the corresponding
user.name) which the user can set so they don't have to specify the argument. The
cli.subcommand() decorator designates this function as a subcommand. The name of the subcommand will be taken from the name of the function.
Once inside our function we find a typical "Hello, World!" program. We use
cli.log to access the underlying Logger Object, whose behavior is user controllable. We also access the value for name supplied by the user as
cli.config.hello.name. The value for
cli.config.hello.name will be determined by looking at the
--name argument supplied by the user, if not provided it will use the value in the
qmk.ini config file, and if neither of those is provided it will fall back to the default supplied in the
MILC and the QMK CLI have several nice tools for interacting with the user. Using these standard tools will allow you to colorize your text for easier interactions, and allow the user to control when and how that information is displayed and stored.
There are two main methods for outputting text in a subcommand-
cli.echo(). They operate in similar ways but you should prefer to use
cli.log.info() for most general purpose printing.
You can use special tokens to colorize your text, to make it easier to understand the output of your program. See Colorizing Text below.
Both of these methods support built-in string formatting using python's printf style string format operations. You can use tokens such as
%d within your text strings then pass the values as arguments. See our Hello, World program above for an example.
You should never use the format operator (
%) directly, always pass values as arguments.
cli.log object gives you access to a Logger Object. We have configured our log output to show the user a nice emoji for each log level (or the log level name if their terminal does not support unicode.) This way the user can tell at a glance which messages are most important when something goes wrong.
The default log level is
INFO. If the user runs
qmk -v <subcommand> the default log level will be set to
Sometimes you simply need to print text outside of the log system. This is appropriate if you are outputting fixed data or writing out something that should never be logged. Most of the time you should prefer
You can colorize the output of your text by including color tokens within text. Use color to highlight, not to convey information. Remember that the user can disable color, and your subcommand should still be usable if they do.
You should generally avoid setting the background color, unless it's integral to what you are doing. Remember that users have a lot of preferences when it comes to their terminal color, so you should pick colors that work well against both black and white backgrounds.
Colors prefixed with 'fg' will affect the foreground (text) color. Colors prefixed with 'bg' will affect the background color.
There are also control sequences that can be used to change the behavior of ANSI output:
Make the text brighter
Make the text dimmer
Make the text normal (neither
Reset all text attributes to default. (This is automatically added to the end of every string.)
Reset the background color to the user's default
Reset the foreground color to the user's default
QMK handles the details of argument parsing and configuration for you. When you add a new argument it is automatically incorporated into the config tree based on your subcommand's name and the long name of the argument. You can access this configuration in
cli.config, using either attribute-style access (
cli.config.<subcommand>.<argument>) or dictionary-style access (
Under the hood QMK uses ConfigParser to store configurations. This gives us an easy and straightforward way to represent the configuration in a human-editable way. We have wrapped access to this configuration to provide some nicities that ConfigParser does not normally have.
You can interact with
cli.config in all the ways you'd normally expect. For example the
qmk compile command gets the keyboard name from
cli.config.compile.keyboard. It does not need to know whether that value came from the command line, an environment variable, or the configuration file.
Iteration is also supported:
for section in cli.config:for key in cli.config[section]:cli.log.info('%s.%s: %s', section, key, cli.config[section][key])
You can set configuration values in the usual ways.
cli.config['<section>']['<key>'] = <value>
cli.config.<section>.<key> = <value>
You can delete configuration values in the usual ways.
The configuration is not written out when it is changed. Most commands do not need to do this. We prefer to have the user change their configuration deliberitely using
You can use
cli.save_config() to write out the configuration.
Some arguments should not be propagated to the configuration file. These can be excluded by adding
arg_only=True when creating the argument.
@cli.argument('-o', '--output', arg_only=True, help='File to write to')@cli.argument('filename', arg_only=True, help='Configurator JSON file')@cli.subcommand('Create a keymap.c from a QMK Configurator export.')def json_keymap(cli):pass
You will only be able to access these arguments using
cli.args. For example:
cli.log.info('Reading from %s and writing to %s', cli.args.filename, cli.args.output)