Read command-line options in Wolfram Language (a.k.a. Mathematica)

Documentation

GetOps[argv, spec] extracts values of argv list according to spec list. argv is a list of strings representing command-line arguments (excluding the program name).

Supported formats of an option with a value both for long and short options are: -o val, -o=val, and -o:val. Terse form like -n10 is supported for short options. Option bundling (-abc as -a -b -c) may be used for single-letter options. An option requiring a value must be the last one in a bundle, if any; in this case, a value may be stuck to the bundle, each of the following is legal: -abcn10, -abcn=10, -abcn:10, -abcn 10.

If several same-key options appear, the last one wins (count option behaves differently, see below).

Returns list of two lists { {key -> value, ...}, {positionalArgs, ...} }.

spec is a list or association of option specifications, each being of the form name -> type where name is either

• string option like one-letter "o" or long "option" for -o or --option, or

• non-empty list of synonymic strings, which means either of them works. The first element is considered as a key.

One or two leading dashes in a specification are optional: o, -o, and --o are the same. A one-letter option still may be used as if it were a long one.

type specifies the option type and default value. Supported types are:

• With a value:

  • string: type is either GOMandatory for mandatory option (yes, oxymoron, but supported), or any value declaring the default value. The string passed is returned as is.

  • converted value: type is either func -> GOMandatory or func -> value. Like previous, but given string is passed to func converter to get the final value. The default value given is not converted and is returned as is.

• Without a value:

  • flag: type is GOFlag. Returns True if the option appears at least once. Once set, it is not unsetteble. See switch below.

  • switch: type is either False or True. Switches on if used as ++option, +-option, or +o. +abc makes a, b, and c all be True. Switches off on --option or -o. The rightmost conflicting option wins.

  • count: type is GOCount. Returns number of appearances of the option. -oo --option gives -option -> 3.

GetOpts may take one option Orderless. If False (default), first non-option found stops scanning options; all to th eright is considered positional arguments. If True, options and positional arguments may be interleaved. Scanning options stops at -- in either case.

Sample usage

Load the package:

Needs["GetOps`"];

Set option specification:

spec = {
  {"mand", "m"} -> GOMandatory,
  {"opt", "o"} -> "some default value",
  {"count", "c", "n"} -> GOCount,
   "flag" -> GOFlag,
   "switch" -> False
};

Get command-line options:

argv = Rest[$CommandLine];
(* or *)
argv = "one two --mand=0 --count -cn ++switch \
        three -oval -m:1 -- \
        --some--positional--arg--" // StringSplit;

Get result:

GetOpts[argv, spec, Orderless -> True]  ⟶  {
  {"mand" -> "1",
   "opt" -> "val",
   "count" -> 3,
   "flag" -> False,
   "switch" -> True},
  {"one", "two", "three", "--some--positional--arg--"}
}