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Command-line option parsing.


The getopt-long library implements command line option parsing, in the spirit of the GNU C library function getopt_long. Both long and short options are supported.

The theory is that people should be able to constrain the set of options they want to process using a grammar, rather than some arbitrary structure. The grammar makes the option descriptions easy to read.

Command-line option grammar

The option grammar is an s-expression of the form:

              (PROPERTY VALUE) ...) 

Each OPTION-NAME should be a symbol. Given this grammar, getopt-long will then accept a command-line option named --OPTION-NAME.

If DOCSTRING is provided, it must be a string containing a brief description of the option.

Each option can have the following (PROPERTY VALUE) pairs:

(single-char CHAR)
Accept -CHAR as a single-character equivalent to --OPTION. This is how to specify traditional Unix-style flags.
(required? BOOL)
If BOOL is true, the option is required. getopt-long will raise an error if it is not found in the list of arguments.
(value FLAG [(PROPERTY VALUE) ...])
If FLAG is #t, the option requires a value; if it is #f, it does not; if it is of the form (REQUIRED name) then the option requires and the name is used by the usage procedure if it is of the form (OPTIONAL name) the option may appear with or without a (named) value.

In addition, the following properties can be defined for a value:

(predicate FUNC)
If the option accepts a value (i.e. you specified (value #t) for this option), then getopt-long will apply FUNC to the value, and throw an exception if it returns #f. FUNC should be a procedure which accepts a string and returns a boolean value; you may need to use quasiquotes to get it into the grammar.
(transformer FUNC)
If the option accepts a value, then getopt will apply FUNC to the string provided on the command line, and put the resulting value in the list of parsed options returned by getopt-long.

The (PROPERTY VALUE) pairs may occur in any order, but each property may occur only once. By default, options do not have single-character equivalents, are not required, and do not take values.

Library Procedures

getopt-long is a procedure for parsing command-line arguments in a manner consistent with GNU programs.

usage is a procedure that creates help strings given a grammar for the command-line arguments.

[procedure] (getopt-long ARGS GRAMMAR)

Parse the arguments ARGS according to the argument list grammar GRAMMAR.

ARGS should be a list of strings. Its first element should be the name of the program; subsequent elements should be the arguments that were passed to the program on the command line. The program-arguments procedure returns a list of this form.

In ARGS, single-character options may be combined, in the usual Unix fashion: ("-x" "-y") is equivalent to ("-xy"). If an option accepts values, then it must be the last option in the combination; the value is the next argument. So, for example, using the following grammar:

    ((apples    (single-char #\a))
     (blimps    (single-char #\b) (value #t))
     (catalexis (single-char #\c) (value #t)))

the following argument lists would be acceptable:

  ("-a" "-b" "bang" "-c" "couth")     ("bang" and "couth" are the values
                                       for "blimps" and "catalexis")
  ("-ab" "bang" "-c" "couth")         (same)
  ("-ac" "couth" "-b" "bang")         (same)
  ("-abc" "couth" "bang")             (an error, since `-b' is not the
                                       last option in its combination)

If an option's value is optional, then getopt-long decides whether it has a value by looking at what follows it in ARGS. If the next element is does not appear to be an option itself, then that element is the option's value.

The value of a long option can can only follow the option name, separated by an `=' character.

If the option "--" appears in ARGS, argument parsing stops there; subsequent arguments are returned as ordinary arguments, even if they resemble options. So, in the argument list:

       ("--apples" "Granny Smith" "--" "--blimp" "Goodyear")

getopt-long will recognize the `apples' option as having the value "Granny Smith", but it will not recognize the `blimp' option; it will return the strings "--blimp" and "Goodyear" as ordinary argument strings.

The getopt-long function returns an option dispatch function that takes in an option name --- one of the symbols from GRAMMAR --- and returns a single value (if the named option has been given once), a list of values (if the option was given multiple times), or #f if the option was not given.

There is a special item in the dispatch function with a key @:

this is the list of arguments that are not options or option values.

getopt-long throws an exception if:


(define grammar
 `((lockfile-dir (required? #t)
                 (value #t)
                 (single-char #\k)
                 (value (required DIR)
                        (predicate ,directory?)))

   (verbose (required? #f)
            (single-char #\v)
            (value #f))

   (x-includes (single-char #\x)
            value #t))

   (rnet-server (single-char #\y)
                (value (required SERVER)
                (predicate ,string?)))

 (getopt-long '("my-prog" "-vk" "/tmp" "foo1" "--x-includes=/usr/include"
                "--rnet-server=lamprod" "--" "-fred" "foo2" "foo3")


Version History


The getopt-long library was originally written by Russ McManus and rewritten by Thien-Thi Nguyen.

getopt-long was ported to Chicken Scheme and extensively modified by Ivan Raikov.

Copyright 2009-2010 Ivan Raikov.

Portions copyright (C) 1998, 2001, 2006 Free Software Foundation,

This program is free software: you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public License
as published by the Free Software Foundation, either version 3 of
the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
General Public License for more details.

A full copy of the Lesser GPL license can be found at