minimalistic parser of command line arguments

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Mark Karpov



Unix-style command line options parser

License MIT Build Status Quicklisp

This is a minimalistic parser of command line options. The main advantage of the library is the ability to concisely define command line options once and then use this definition for parsing and extraction of command line arguments, as well as printing description of command line options (you get --help for free). This way you don't need to repeat yourself. Also, unix-opts doesn't depend on anything and allows to precisely control behavior of the parser via Common Lisp restarts.

Inspired by Haskell's optparse-applicative and Python's argparse.

It is portable accross implementations.


Copy files of this library in any place where ASDF can find them. Then you can use it in system definitions and ASDF will take care of the rest.

Via Quicklisp (recommended):

(ql:quickload "unix-opts")

Now you can also use its shorter nickname opts.


option condition

Take a condition condition (unknown-option, missing-arg, or arg-parser-failed) and return a string representing the option in question.

raw-arg condition

Take a condition of type arg-parser-failed and return the raw argument string.

define-opts &rest descriptions

Define command line options. Arguments of this macro must be plists containing various parameters. Here we enumerate all allowed parameters:

  • :name—keyword that will be included in list returned by get-opts function if actual option is supplied by user.

  • :description—description of the option (it will be used in describe function). This argument is optional, but it's recommended to supply it.

  • :short—single character, short variant of the option. You may omit this argument if you supply :long variant of option.

  • :long—string, long variant of option. You may omit this argument if you supply :short variant of option.

  • :arg-parser—if actual option must take an argument, supply this argument, it must be a function that takes a string and parses it.

  • :meta-var—if actual option requires an argument, this is how it will be printed in option description.

  • :required—whether the option is required. This only makes sense if the option takes an argument.

  • :default—the default value used if the option was not found. This can either be a function (which will be called to generate the default value) or a literal value. This option cannot be combined with :required. The default value will not be provided to the arg-parser.


Return a list of the program's arguments, including the command used to execute the program as the first element of the list. Portable across implementations.

get-opts &optional options

Parse command line options. If options is given, it should be a list to parse. If it's not given, the function will use the argv function to get the list of command line arguments.

Returns two values:

  • a list that contains keywords associated with command line options with define-opts macro, and
  • a list of free arguments.

If some option requires an argument, you can use getf to test the presence of the option and get its argument if the option is present.

The parser may signal various conditions. Let's list them all specifying which restarts are available for every condition, and what kind of information the programmer can extract from the conditions.

  • unknown-option is thrown when the parser encounters an unknown (not previously defined with define-opts) option. Use the option reader to get the name of the option (string). Available restarts: use-value (substitute the option and try again), skip-option (ignore the option).

  • missing-arg is thrown when some option wants an argument, but there is no such argument given. Use the option reader to get the name of the option (string). Available restarts: use-value (supplied value will be used), skip-option (ignore the option).

  • arg-parser-failed is thrown when some option wants an argument, it's given but cannot be parsed by argument parser. Use the option reader to get name of the option (string) and raw-arg to get raw string representing the argument before parsing. Available restarts: use-value (supplied value will be used), skip-option (ignore the option), reparse-arg (supplied string will be parsed instead).

  • missing-required-option is thrown when a required option cannot be found. Use the missing-options reader to get all option objects that are missing. Available restarts: use-value (supplied list of values will be used), skip-option (ignore all these options, effectively binding them to nil)

describe &key prefix suffix usage-of args stream

Return a string describing all the options of the program that were defined with the previous define-opts macro. You can supply prefix and suffix arguments that will be printed before and after the options respectively. If usage-of is supplied, it should be a string, the name of the program for an "Usage: " section. This section is only printed if this name is given. If your program takes arguments (apart from options), you can specify how to print them in "Usage: " section with an args option (should be a string designator). Output goes to stream (default value is *standard-output*).

exit &optional (status 0)

Exit the program returning status.


Go to the example directory. Now, you can use example.lisp file to see if unix-opts is cool enough for you to use. SBCL users can use example.sh file.

Take a look at example.lisp and you will see that the library is pretty sexy! Basically, we have defined all the options just like this:

  (:name :help
   :description "print this help text"
   :short #\h
   :long "help")
  (:name :verbose
   :description "verbose output"
   :short #\v
   :long "verbose")
  (:name :level
   :description "the program will run on LEVEL level"
   :short #\l
   :long "level"
   :required t
   :arg-parser #'parse-integer
   :meta-var "LEVEL")
  (:name :output
   :description "redirect output to file FILE"
   :short #\o
   :long "output"
   :arg-parser #'identity
   :meta-var "FILE"))

and we read them with (opts:get-opts) which returns two values, a list of parsed options and the remaining arguments, so:

(multiple-value-bind (options free-args)
  (if (getf options :verbose)

See the example for helpers and how to handle malformed or incomplete arguments.

And here is some action:

$ sh example.sh --help
example—program to demonstrate unix-opts library

Usage: example.sh [-h|--help] [-v|--verbose] [-l|--level LEVEL]
                  [-o|--output FILE] [FREE-ARGS]

Available options:
  -h, --help               print this help text
  -v, --verbose            verbose output
  -l, --level LEVEL        the program will run on LEVEL level
  -o, --output FILE        redirect output to file FILE

so that's how it works…
free args:

$ sh example.sh --level 1 -v file1.txt file2.txt
OK, running in verbose mode…
I see you've supplied level option, you want 1 level!
free args: file1.txt, file2.txt

$ sh example.sh --level 10 --output foo.txt bar.txt
I see you've supplied level option, you want 10 level!
I see you want to output the stuff to "foo.txt"!
free args: bar.txt

$ sh example.sh --level kitty foo.txt
fatal: cannot parse "kitty" as argument of "--level"
free args:

$ sh example.sh --hoola-boola noola.txt
warning: "--hoola-boola" option is unknown!
fatal: missing required options: "--level"

$ sh example.sh -vgl=10
warning: "-g" option is unknown!
OK, running in verbose mode…
I see you've supplied level option, you want 10 level!
free args:


Copyright © 2015–2018 Mark Karpov

Distributed under MIT License.

Dependencies (0)

    Dependents (4)

    • cl-skkserv
    • cl-torrents
    • cl-webmachine
    • replic
    • GitHub
    • Quicklisp