options.md

Argument and Flag Options

Arguments and Flags both accept a handful of options. Comon option types are enumerated below.

Completers

To activate autocompletion for arguments and flags, Completer objects can be passed in as options. See the autocompletion doc for more details.

commander.Default

This argument option sets the argument's value (only useful for optional arguments and flags).

var (
  optionalFloat = commander.OptionalArg[float64]("N", "An optional float argument", commander.Default[float64](12.3))

  stringFlag = commander.Flag[string]("STRING", 's', "A string flag", commander.Default[string]("default value"))

command.CustomSetter

By default, the value provided is simply stored in the command.Data.Values map with the argument/flag name as the key. If you wish to override this behavior, you can provide a CustomSetter to do custom logic with the value.

command.Transformer

A Transformer transforms the argument/flag's value. For example, FileTransformer() transforms a relative filepath into it's full absolute path (which is useful for shortcuts).

command.Validator

A Validator validates an input. Each argument/flag can have as many valiadators as is necessary. If validation fails, a useful error message will be sent to stderr. See below for validator examples:

var (
  // An integer that must be positive
  positiveInt = commander.Arg[int]("N", "An int argument", commander.Positive())
  // A string argument that must be at least 8 characters long.
  username = commander.Arg[string]("USERNAME", "Your username", command.MinLength(8))
)