small library to deal with command-line arguments

Upstream URL


Francois-Rene Rideau


Eric Schulte




A library for parsing command-line arguments.

Use it in conjunction with asdf:program-op or cl-launch for portable processing of command-line arguments.


This library is woefully under-documented. See the examples below, and read the source code for details. Here is what a prototypical use looks like:

(defparameter +command-line-spec+
  '(((#\b) :type boolean :optional t :documentation "what optional -b flag does")
    (("check" #\c) :type string :optional t :documentation "a --check or -c flag that takes a string")
    (("verbose") :type boolean :optional t :documentation "only a verbose --verbose is accepted")
    (("warn" "warning" #\w) :type boolean :optional t :documentation "multiple spellings possible")
    (("help" #\h #\?) :type boolean :optional t :documentation "--help -h -?, good practice to have")
    (("version" #\V) :type boolean :optional t :documentation "--version or -V, you get the idea")))

;; for the positional arguments, see below :positional-arity and :rest-arity
(defun my-program-function (arg1 arg2 rest-args &key b check verbose warn help version)
   (when help (show-option-help +command-line-spec+ :sort-names t) (uiop:quit))
   (when version (show-version) (uiop:quit))

(defun main (args)
    ;; the spec as above, or prepared with prepare-command-line-options-specification
    ;; the function to call with the arguments as parsed
    ;; the arguments to parse
    :command-line args
    ;; the program name to use in case of an error message
    :name "my-program"
    ;; the number of mandatory positional arguments for this command (default: 0)
    :positional-arity 2
    ;; What to do with the rest of the positional arguments.
    ;; T means pass the list of the rest of the command-line-arguments as one lisp argument.
    ;; NIL means ignore it. A keyword means pass this rest as a keyword argument.
    :rest-arity t))

The define-command macro may be used to simultaneously define the following three functions which are useful for defining a function which may be invoked from the command line. For example, the following invocation of define-command on FOO results in:

(define-command foo (noun verb &spec +command-line-spec+ &aux scratch)
  "Usage: foo NOUN VERB [OPTIONS...]
Do VERB to NOUN according to OPTIONS."
  #.(format nil "~%Built with ~a version ~a.~%"
  (declare (verbose))
  (when help (show-help-for-foo))

show-help-for-FOO : Prints help and option information for FOO to STDOUT and then exits with uiop:quit.

The docstring passed to `define-command` becomes the help text
printed before options.  A second docstring passed as the fourth
argument to `define-command` is printed after the options.

run-FOO : Similar to the main example above this function is meant to be used as a defsystem :entry-point. It runs FOO on the command line arguments by invoking handle-command-line.

FOO : The &body passed to define-command becomes the body of the FOO function. The positional required command line arguments become named arguments to FOO and the command line options passed in behind the &spec keyword in the argument list become keyword arguments to FOO. When supplied :initial-value properties of command lines become defaults of the corresponding keyword arguments. When supplied :action properties of command line arguments have calls to their actions prepended to the body of the function. Actions are only called when the keyword argument has a non-nil value.

The macro-expanded prototype for FOO in this example would be the



For very simple examples of actual uses, see my tthsum clone in Lisp or my workout-timer.

For a much more elaborate use, see xcvb — unhappily, XCVB has gone mostly unmaintained since 2012, so the example might not be usefully runnable.


See also

For a fancier take on the same general idea, see Didier Verna's CLON:

CLON has much more features than this library, but is much more complex and slighly less portable.

Dependencies (2)

  • alexandria
  • hu.dwim.stefil
  • GitHub
  • Quicklisp
  • Sponsor