Isn't it awesome how CommandLineParser and PowerArgs generate help messages based on your code?!
Hell no! You know what's awesome? It's when the option parser is generated based on the beautiful help message that you write yourself! This way you don't need to write this stupid repeatable parser-code, and instead can write only the help message--the way you want it.
docopt.net helps you create most beautiful command-line interfaces easily:
using System;
using DocoptNet;
namespace NavalFate
{
internal class Program
{
private const string usage = @"Naval Fate.
Usage:
naval_fate.exe ship new <name>...
naval_fate.exe ship <name> move <x> <y> [--speed=<kn>]
naval_fate.exe ship shoot <x> <y>
naval_fate.exe mine (set|remove) <x> <y> [--moored | --drifting]
naval_fate.exe (-h | --help)
naval_fate.exe --version
Options:
-h --help Show this screen.
--version Show version.
--speed=<kn> Speed in knots [default: 10].
--moored Moored (anchored) mine.
--drifting Drifting mine.
";
private static void Main(string[] args)
{
var arguments = new Docopt().Apply(usage, args, version: "Naval Fate 2.0", exit: true);
foreach (var argument in arguments)
{
Console.WriteLine("{0} = {1}", argument.Key, argument.Value);
}
}
}
}Beat that! The option parser is generated based on the docstring above that is
passed to the Docopt.Apply method. Docopt.Apply parses the usage pattern
("Usage: ...") and option descriptions (lines starting with dash "-") and
ensures that the program invocation matches the usage pattern; it parses
options, arguments and commands based on that. The basic idea is that a good
help message has all necessary information in it to make a parser.
-
This port should be fully Docopt language compatible with the python reference implementation.
-
Because C# is statically typed, the return dictionary is of type
IDictionary<string, ValueObject>whereValueObjectis a simple wrapper class around entry values.
Use dotnet
dotnet add package docopt.net
Use nuget
nuget install docopt.net
Under Visual Studio
Just drop DocoptNet.dll file into your project; it is self-contained.
using DocoptNet;public IDictionary<string, ValueObject> Apply(string doc, string cmdLine, bool help = true,
object version = null, bool optionsFirst = false, bool exit = false);
public IDictionary
8000
<string, ValueObject> Apply(string doc, ICollection<string> argv, bool help = true,
object version = null, bool optionsFirst = false, bool exit = false);Apply takes 1 required and 5 optional arguments:
-
docis a string that contains a help message that will be parsed to create the option parser. The simple rules of how to write such a help message are given in next sections. Here is a quick example of such a string:const string USAGE = @"Usage: my_program [-hso FILE] [--quiet | --verbose] [INPUT ...] -h --help show this -s --sorted sorted output -o FILE specify output file [default: ./test.txt] --quiet print less text --verbose print more text ";
-
argvis an optional argument. -
help, by defaulttrue, specifies whether the parser should automatically print the help message (supplied asdoc) and terminate, in case-hor--helpoption is encountered (options should exist in usage pattern, more on that below). If you want to handle-hor--helpoptions manually (as other options), sethelp: false.Note, you can override the print and exit behaviour by providing a custom handler for the
Docopt.PrintExitevent. e.g.var docopt = new Docopt(); docopt.PrintExit += MyCustomPrintExit;
-
version, by defaultnull, is an optional argument that specifies the version of your program. If supplied, then, (assuming--versionoption is mentioned in usage pattern) when parser encounters the--versionoption, it will print the supplied version and terminate.versioncould be any printable object, but most likely a string, e.g."2.1.0rc1".Note, when
docopt.netis set to automatically handle-h,--helpand--versionoptions, you still need to mention them in usage pattern for this to work. Also, for your users to know about them. -
optionsFirst, by defaultfalse. If set totruewill disallow mixing options and positional argument; i.e. after first positional argument, all arguments will be interpreted as positional even if they look like options. This can be used for strict compatibility with POSIX, or if you want to dispatch your arguments to other programs. -
exit, by defaultfalse. If set tofalsewill raise exceptions based onDocoptBaseExceptionand will not print or exit. If set totrueany occurence ofDocoptBaseExceptionwill be caught byDocopt.Apply(), the error message or the usage will be printed, and the program will exit with error code 0 if it's aDocoptExitException, 1 otherwise.
The return value is a simple dictionary with options, arguments and commands as keys, spelled exactly like in your help message. Long versions of options are given priority. For example, if you invoke the top example as:
naval_fate ship Guardian move 100 150 --speed=15
the return dictionary will be:
{
["--drifting"] = false, ["mine"] = false,
["--help"] = false, ["move"] = true,
["--moored"] = false, ["new"] = false,
["--speed"] = "15", ["remove"] = false,
["--version"] = false, ["set"] = false,
["<name>"] = ["Guardian"], ["ship"] = true,
["<x>"] = "100", ["shoot"] = false,
["<y>"] = "150"
}Help message consists of 2 parts:
-
Usage pattern, e.g.:
Usage: my_program [-hso FILE] [--quiet | --verbose] [INPUT ...] -
Option descriptions, e.g.:
-h --help show this -s --sorted sorted output -o FILE specify output file [default: ./test.txt] --quiet print less text --verbose print more text
Their format is described below; other text is ignored.
Usage pattern is a substring of doc that starts with usage: (case
insensitive) and ends with a visibly empty line. Minimum example:
const string USAGE = "Usage: my_program";The first word after usage: is interpreted as your program's name. You can
specify your program's name several times to signify several exclusive patterns:
const string USAGE =
@"Usage: my_program FILE
my_program COUNT FILE";Each pattern can consist of the following elements:
-
<arguments>, ARGUMENTS. Arguments are specified as either upper-case words, e.g.
my_program CONTENT-PATHor words surrounded by angular brackets:my_program <content-path>. -
--options. Options are words started with dash (
-), e.g.--output,-o. You can "stack" several of one-letter options, e.g.-oivwhich will be the same as-o -i -v. The options can have arguments, e.g.--input=FILEor-i FILEor even-iFILE. However it is important that you specify option descriptions if you want your option to have an argument, a default value, or specify synonymous short/long versions of the option (see next section on option descriptions). -
commands are words that do not follow the described above conventions of
--optionsor<arguments>orARGUMENTS, plus two special commands: dash "-" and double dash "--" (see below).
Use the following constructs to specify patterns:
-
[ ] (brackets) optional elements. e.g.:
my_program [-hvqo FILE] -
( ) (parens) required elements. All elements that are not put in [ ] are also required, e.g.:
my_program --path=<path> <file>...is the same asmy_program (--path=<path> <file>...). (Note, "required options" might be not a good idea for your users). -
| (pipe) mutually exclusive elements. Group them using ( ) if one of the mutually exclusive elements is required:
my_program (--clockwise | --counter-clockwise) TIME. Group them using [ ] if none of the mutually-exclusive elements are required:my_program [--left | --right]. -
... (ellipsis) one or more elements. To specify that arbitrary number of repeating elements could be accepted, use ellipsis (
...), e.g.my_program FILE ...means one or moreFILE-s are accepted. If you want to accept zero or more elements, use brackets, e.g.:my_program [FILE ...]. Ellipsis works as a unary operator on the expression to the left. -
[options] (case sensitive) shortcut for any options. You can use it if you want to specify that the usage pattern could be provided with any options defined below in the option-descriptions and do not want to enumerate them all in usage-pattern.
-
"
[--]". Double dash "--" is used by convention to separate positional arguments that can be mistaken for options. In order to support this convention add "[--]" to your usage patterns. -
"
[-]". Single dash "-" is used by convention to signify thatstdinis used instead of a file. To support this add "[-]" to your usage patterns. "-" acts as a normal command.
If your pattern allows to match argument-less option (a flag) several times:
Usage: my_program [-v | -vv | -vvv]
then number of occurrences of the option will be counted; i.e. args['-v'] will
be 2 if program was invoked as my_program -vv. Same works for commands.
If your usage patterns allows to match same-named option with argument or positional argument several times, the matched arguments will be collected into a list:
Usage: my_program <file> <file> --path=<path>...
Therefore invoked with my_program file1 file2 --path=./here --path=./there the
returned dict will contain args['<file>'] == ['file1', 'file2'] and
args['--path'] == ['./here', './there'].
Option descriptions consist of a list of options that you put below your usage patterns.
It is necessary to list option descriptions in order to specify:
- synonymous short and long options,
- if an option has an argument,
- if option's argument has a default value.
The rules are as follows:
-
Every line in
docthat starts with-or--(not counting spaces) is treated as an option description, e.g.:Options: --verbose # GOOD -o FILE # GOOD Other: --bad # BAD, line does not start with dash "-" -
To specify that option has an argument, put a word describing that argument after space (or equals "
=" sign) as shown below. Follow either <angular-brackets> or UPPER-CASE convention for options' arguments. You can use comma if you want to separate options. In the example below, both lines are valid, however you are recommended to stick to a single style.:-o FILE --output=FILE # without comma, with "=" sign -i <file>, --input <file> # with comma, without "=" sing -
Use two spaces to separate options with their informal description:
--verbose More text. # BAD, will be treated as if verbose option had # an argument "More", so use 2 spaces instead -q Quit. # GOOD -o FILE Output file. # GOOD --stdout Use stdout. # GOOD, 2 spaces -
If you want to set a default value for an option with an argument, put it into the option-description, in form
[default: <my-default-value>]:--coefficient=K The K coefficient [default: 2.95] --output=FILE Output file [default: test.txt] --directory=DIR Some directory [default: ./] -
If the option is not repeatable, the value inside
[default: ...]will be interpreted as string. If it is repeatable, it will be splited into a list on whitespace:Usage: my_program [--repeatable=<arg> --repeatable=<arg>] [--another-repeatable=<arg>]... [--not-repeatable=<arg>] # will be ['./here', './there'] --repeatable=<arg> [default: ./here ./there] # will be ['./here'] --another-repeatable=<arg> [default: ./here] # will be './here ./there', because it is not repeatable --not-repeatable=<arg> [default: ./here ./there]