yargs
========

Yargs be a node.js library fer hearties tryin' ter parse optstrings.

With yargs, ye be havin' a map that leads straight to yer treasure! Treasure of course, being a simple option hash.

[![Build Status](https://travis-ci.org/chevex/yargs.png)](https://travis-ci.org/chevex/yargs)
[![Dependency Status](https://gemnasium.com/chevex/yargs.png)](https://gemnasium.com/chevex/yargs)
[![NPM version](https://badge.fury.io/js/yargs.png)](http://badge.fury.io/js/yargs)

> ~~NOTE: Yargs is a fork of [optimist](https://github.com/substack/node-optimist) by [substack (James Halliday)](https://github.com/substack). It is obvious that substack is stretched pretty thin maintaining over 300 modules on npm at the time of this writing. So rather than complain in the project issue tracker I thought I'd just pick up the torch and maintain a proper fork. Currently the project is totally backward compatible with optimist but this may change in the future (if it does I will update this notice to inform you of this). For now though, enjoy optimist with about 5 months worth of fixes and updates rolled in, most of them pulled from optimist's own [stale pull requests](https://github.com/substack/node-optimist/pulls).~~

> UPDATE: Yargs is now the official successor to optimist. Please feel free to submit issues and pull requests. While I personally don't have the time to pore over all the issues and fix all of them on a regular basis, I'm more than happy to look over pull requests, test them, and merge them in. If you'd like to contribute and don't know where to start, have a look at [the issue list](https://github.com/chevex/yargs/issues) :)

examples
========

With yargs, the options be just a hash!
-------------------------------------------------------------------

xup.js:

````javascript
#!/usr/bin/env node
var argv = require('yargs').argv;

if (argv.rif - 5 * argv.xup > 7.138) {
    console.log('Plunder more riffiwobbles!');
}
else {
    console.log('Drop the xupptumblers!');
}
````

***

    $ ./xup.js --rif=55 --xup=9.52
    Plunder more riffiwobbles!
    
    $ ./xup.js --rif 12 --xup 8.1
    Drop the xupptumblers!

![Joe was one optimistic pirate.](http://i.imgur.com/4WFGVJ9.png)

But don't walk the plank just yet! There be more! You can do short options:
-------------------------------------------------
 
short.js:

````javascript
#!/usr/bin/env node
var argv = require('yargs').argv;
console.log('(%d,%d)', argv.x, argv.y);
````

***

    $ ./short.js -x 10 -y 21
    (10,21)

And booleans, both long, short, and even grouped:
----------------------------------

bool.js:

````javascript
#!/usr/bin/env node
var util = require('util');
var argv = require('yargs').argv;

if (argv.s) {
    util.print(argv.fr ? 'Le perroquet dit: ' : 'The parrot says: ');
}
console.log(
    (argv.fr ? 'couac' : 'squawk') + (argv.p ? '!' : '')
);
````

***

    $ ./bool.js -s
    The parrot says: squawk
    
    $ ./bool.js -sp
    The parrot says: squawk!

    $ ./bool.js -sp --fr
    Le perroquet dit: couac!

And non-hyphenated options too! Just use `argv._`!
-------------------------------------------------
 
nonopt.js:

````javascript
#!/usr/bin/env node
var argv = require('yargs').argv;
console.log('(%d,%d)', argv.x, argv.y);
console.log(argv._);
````

***

    $ ./nonopt.js -x 6.82 -y 3.35 rum
    (6.82,3.35)
    [ 'rum' ]
    
    $ ./nonopt.js "me hearties" -x 0.54 yo -y 1.12 ho
    (0.54,1.12)
    [ 'me hearties', 'yo', 'ho' ]

Yargs even counts your booleans!
----------------------------------------------------------------------

count.js

````javascript
#!/usr/bin/env node
var argv = require('yargs')
    .count('verbose')
    .alias('v', 'verbose')
    .argv;

VERBOSE_LEVEL = argv.verbose;

function WARN()  { VERBOSE_LEVEL >= 0 && console.log.apply(console, arguments); }
function INFO()  { VERBOSE_LEVEL >= 1 && console.log.apply(console, arguments); }
function DEBUG() { VERBOSE_LEVEL >= 2 && console.log.apply(console, arguments); }

WARN("Showing only important stuff");
INFO("Showing semi-mportant stuff too");
DEBUG("Extra chatty mode");
````

***
    $ node count.js
    Showing only important stuff

    $ node count.js -v
    Showing only important stuff
    Showing semi-important stuff too

    $ node count.js -vv
    Showing only important stuff
    Showing semi-important stuff too
    Extra chatty mode

    $ node count.js -v --verbose
    Showing only important stuff
    Showing semi-important stuff too
    Extra chatty mode

Tell users how to use yer options and make demands.
-------------------------------------------------

divide.js:

````javascript
#!/usr/bin/env node
var argv = require('yargs')
    .usage('Usage: $0 -x [num] -y [num]')
    .demand(['x','y'])
    .argv;

console.log(argv.x / argv.y);
````

***
 
    $ ./divide.js -x 55 -y 11
    5
    
    $ node ./divide.js -x 4.91 -z 2.51
    Usage: node ./divide.js -x [num] -y [num]

    Options:
      -x  [required]
      -y  [required]

    Missing required arguments: y

After yer demands have been met, demand more! Ask for non-hypenated arguments!
-----------------------------------------

demand_count.js:

````javascript
#!/usr/bin/env node
var argv = require('yargs')
    .demand(2)
    .argv;
console.dir(argv)
````

***

	$ ./demand_count.js a
	Not enough arguments, expected 2, but only found 1
	$ ./demand_count.js a b
	{ _: [ 'a', 'b' ], '$0': 'node ./demand_count.js' }
	$ ./demand_count.js a b c
	{ _: [ 'a', 'b', 'c' ], '$0': 'node ./demand_count.js' }

EVEN MORE SHIVER ME TIMBERS!
------------------

default_singles.js:

````javascript
#!/usr/bin/env node
var argv = require('yargs')
    .default('x', 10)
    .default('y', 10)
    .argv
;
console.log(argv.x + argv.y);
````

***

    $ ./default_singles.js -x 5
    15

default_hash.js:

````javascript
#!/usr/bin/env node
var argv = require('yargs')
    .default({ x : 10, y : 10 })
    .argv
;
console.log(argv.x + argv.y);
````

***

    $ ./default_hash.js -y 7
    17

And if you really want to get all descriptive about it...
---------------------------------------------------------

boolean_single.js

````javascript
#!/usr/bin/env node
var argv = require('yargs')
    .boolean('v')
    .argv
;
console.dir(argv.v);
console.dir(argv._);
````

***

    $ ./boolean_single.js -v "me hearties" yo ho
    true
    [ 'me hearties', 'yo', 'ho' ]
    

boolean_double.js

````javascript
#!/usr/bin/env node
var argv = require('yargs')
    .boolean(['x','y','z'])
    .argv
;
console.dir([ argv.x, argv.y, argv.z ]);
console.dir(argv._);
````

***

    $ ./boolean_double.js -x -z one two three
    [ true, false, true ]
    [ 'one', 'two', 'three' ]

Yargs is here to help you...
---------------------------

Ye can describe parameters fer help messages and set aliases. Yargs figures
out how ter format a handy help string automatically.

line_count.js

````javascript
#!/usr/bin/env node
var argv = require('yargs')
    .usage('Count the lines in a file.\nUsage: $0')
    .example('$0 -f', 'count the lines in the given file')
    .demand('f')
    .alias('f', 'file')
    .describe('f', 'Load a file')
    .argv
;

var fs = require('fs');
var s = fs.createReadStream(argv.file);

var lines = 0;
s.on('data', function (buf) {
    lines += buf.toString().match(/\n/g).length;
});

s.on('end', function () {
    console.log(lines);
});
````

***

    $ node line_count.js
    Count the lines in a file.
    Usage: node ./line_count.js

    Examples:
      node ./line_count.js -f   count the lines in the given file

    Options:
      -f, --file  Load a file  [required]

    Missing required arguments: f

    $ node line_count.js --file line_count.js 
    20
    
    $ node line_count.js -f line_count.js 
    20

methods
=======

By itself,

````javascript
require('yargs').argv
`````

will use `process.argv` array to construct the `argv` object.

You can pass in the `process.argv` yourself:

````javascript
require('yargs')([ '-x', '1', '-y', '2' ]).argv
````

or use .parse() to do the same thing:

````javascript
require('yargs').parse([ '-x', '1', '-y', '2' ])
````

The rest of these methods below come in just before the terminating `.argv`.

.alias(key, alias)
------------------

Set key names as equivalent such that updates to a key will propagate to aliases
and vice-versa.

Optionally `.alias()` can take an object that maps keys to aliases.
Each key of this object should be the canonical version of the option, and each
value should be a string or an array of strings.

.default(key, value)
--------------------

Set `argv[key]` to `value` if no option was specified on `process.argv`.

Optionally `.default()` can take an object that maps keys to default values.

.demand(key, [msg | boolean])
-----------------------------
.require(key, [msg | boolean])
------------------------------
.required(key, [msg | boolean])
-------------------------------

If `key` is a string, show the usage information and exit if `key` wasn't
specified in `process.argv`.

If `key` is a number, demand at least as many non-option arguments, which show
up in `argv._`.

If `key` is an Array, demand each element.

If a `msg` string is given, it will be printed when the argument is missing,
instead of the standard error message. This is especially helpful for the non-option arguments in `argv._`.

If a `boolean` value is given, it controls whether the option is demanded;
this is useful when using `.options()` to specify command line parameters.

.requiresArg(key)
-----------------

Specifies either a single option key (string), or an array of options that
must be followed by option values. If any option value is missing, show the
usage information and exit.

The default behaviour is to set the value of any key not followed by an
option value to `true`.

.describe(key, desc)
--------------------

Describe a `key` for the generated usage information.

Optionally `.describe()` can take an object that maps keys to descriptions.

.options(key, opt)
------------------

Instead of chaining together `.alias().demand().default()`, you can specify
keys in `opt` for each of the chainable methods.

For example:

````javascript
var argv = require('yargs')
    .options('f', {
        alias : 'file',
        default : '/etc/passwd',
    })
    .argv
;
````

is the same as

````javascript
var argv = require('yargs')
    .alias('f', 'file')
    .default('f', '/etc/passwd')
    .argv
;
````

Optionally `.options()` can take an object that maps keys to `opt` parameters.

.usage(message, opts)
---------------------

Set a usage message to show which commands to use. Inside `message`, the string
`$0` will get interpolated to the current script name or node command for the
present script similar to how `$0` works in bash or perl.

`opts` is optional and acts like calling `.options(opts)`.

.example(cmd, desc)
-------------------

Give some example invocations of your program. Inside `cmd`, the string
`$0` will get interpolated to the current script name or node command for the
present script similar to how `$0` works in bash or perl.
Examples will be printed out as part of the help message.

.check(fn)
----------

Check that certain conditions are met in the provided arguments.

`fn` is called with two arguments, the parsed `argv` hash and an array of options and their aliases.

If `fn` throws or returns `false`, show the thrown error, usage information, and
exit.

.boolean(key)
-------------

Interpret `key` as a boolean. If a non-flag option follows `key` in
`process.argv`, that string won't get set as the value of `key`.

If `key` never shows up as a flag in `process.arguments`, `argv[key]` will be
`false`.

If `key` is an Array, interpret all the elements as booleans.

.string(key)
------------

Tell the parser logic not to interpret `key` as a number or boolean.
This can be useful if you need to preserve leading zeros in an input.

If `key` is an Array, interpret all the elements as strings.

.config(key)
------------

Tells the parser to interpret `key` as a path to a JSON config file. The file
is loaded and parsed, and its properties are set as arguments.

.wrap(columns)
--------------

Format usage output to wrap at `columns` many columns.

.strict()
---------

Any command-line argument given that is not demanded, or does not have a
corresponding description, will be reported as an error.

.help([option, [description]])
------------------------------

Add an option (e.g., `--help`) that displays the usage string and exits the
process. If present, the `description` parameter customises the description of
the help option in the usage string.

If invoked without parameters, `.help` returns the generated usage string.

Example:

```
var yargs = require("yargs")
       .usage("$0 -operand1 number -operand2 number -operation [add|subtract]");
console.log(yargs.help());
```

Later on, ```argv``` can be retrived with ```yargs.argv```

.version(version, option, [description])
----------------------------------------

Add an option (e.g., `--version`) that displays the version number (given by the
`version` parameter) and exits the process. If present, the `description`
parameter customises the description of the version option in the usage string.

.showHelpOnFail(enable, [message])
----------------------------------

By default, yargs outputs a usage string if any error is detected. Use the
`.showHelpOnFail` method to customize this behaviour. if `enable` is `false`,
the usage string is not output. If the `message` parameter is present, this
message is output after the error message.

line_count.js

````javascript
#!/usr/bin/env node
var argv = require('yargs')
    .usage('Count the lines in a file.\nUsage: $0')
    .demand('f')
    .alias('f', 'file')
    .describe('f', 'Load a file')
    .showHelpOnFail(false, "Specify --help for available options")
    .argv;

// etc.
````

***

    $ node line_count.js --file
    Missing argument value: f

    Specify --help for available options

.showHelp(fn=console.error)
---------------------------

Print the usage data using `fn` for printing.

Example:

```
var yargs = require("yargs")
       .usage("$0 -operand1 number -operand2 number -operation [add|subtract]");
yargs.showHelp();
```

Later on, ```argv``` can be retrived with ```yargs.argv```

.parse(args)
------------

Parse `args` instead of `process.argv`. Returns the `argv` object.

.argv
-----

Get the arguments as a plain old object.

Arguments without a corresponding flag show up in the `argv._` array.

The script name or node command is available at `argv.$0` similarly to how `$0`
works in bash or perl.

parsing tricks
==============

stop parsing
------------

Use `--` to stop parsing flags and stuff the remainder into `argv._`.

    $ node examples/reflect.js -a 1 -b 2 -- -c 3 -d 4
    { _: [ '-c', '3', '-d', '4' ],
      '$0': 'node ./examples/reflect.js',
      a: 1,
      b: 2 }

negate fields
-------------

If you want to explicity set a field to false instead of just leaving it
undefined or to override a default you can do `--no-key`.

    $ node examples/reflect.js -a --no-b
    { _: [],
      '$0': 'node ./examples/reflect.js',
      a: true,
      b: false }

numbers
-------

Every argument that looks like a number (`!isNaN(Number(arg))`) is converted to
one. This way you can just `net.createConnection(argv.port)` and you can add
numbers out of `argv` with `+` without having that mean concatenation,
which is super frustrating.

duplicates
----------

If you specify a flag multiple times it will get turned into an array containing
all the values in order.

    $ node examples/reflect.js -x 5 -x 8 -x 0
    { _: [],
      '$0': 'node ./examples/reflect.js',
        x: [ 5, 8, 0 ] }

dot notation
------------

When you use dots (`.`s) in argument names, an implicit object path is assumed.
This lets you organize arguments into nested objects.

     $ node examples/reflect.js --foo.bar.baz=33 --foo.quux=5
     { _: [],
       '$0': 'node ./examples/reflect.js',
         foo: { bar: { baz: 33 }, quux: 5 } }

short numbers
-------------

Short numeric `head -n5` style argument work too:

    $ node reflect.js -n123 -m456
    { '3': true,
      '6': true,
      _: [],
      '$0': 'node ./reflect.js',
      n: 123,
      m: 456 }

installation
============

With [npm](http://github.com/isaacs/npm), just do:

    npm install yargs
 
or clone this project on github:

    git clone http://github.com/chevex/yargs.git

To run the tests with [expresso](http://github.com/visionmedia/expresso),
just do:
    
    expresso

inspired By
===========

This module is loosely inspired by Perl's
[Getopt::Casual](http://search.cpan.org/~photo/Getopt-Casual-0.13.1/Casual.pm).