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Examples

See the Example Folder for more demonstrations of Yargs in the wild. We would love fixes to old examples and pull requests for fancy new examples, help contribute!.

With yargs, the options be just a hash!

plunder.js:

#!/usr/bin/env node
var argv = require('yargs/yargs')(process.argv.slice(2)).argv;

if (argv.ships > 3 && argv.distance < 53.5) {
    console.log('Plunder more riffiwobbles!');
} else {
    console.log('Retreat from the xupptumblers!');
}
$ ./plunder.js --ships=4 --distance=22
Plunder more riffiwobbles!

$ ./plunder.js --ships 12 --distance 98.7
Retreat from the xupptumblers!

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

short.js:

#!/usr/bin/env node
var argv = require('yargs/yargs')(process.argv.slice(2)).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:

#!/usr/bin/env node
var argv = require('yargs/yargs')(process.argv.slice(2)).argv;

if (argv.s) {
    process.stdout.write(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:

#!/usr/bin/env node
var argv = require('yargs/yargs')(process.argv.slice(2)).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:

#!/usr/bin/env node
var argv = require('yargs/yargs')(process.argv.slice(2))
    .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-important 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 your options and make demands.

area.js:

#!/usr/bin/env node
var argv = require('yargs/yargs')(process.argv.slice(2))
    .usage('Usage: $0 -w [num] -h [num]')
    .demandOption(['w','h'])
    .argv;

console.log("The area is:", argv.w * argv.h);
$ ./area.js -w 55 -h 11
The area is: 605

$ node ./area.js -w 4.91 -w 2.51
Usage: area.js -w [num] -h [num]

Options:
  -w  [required]
  -h  [required]

Missing required arguments: h

After your demands have been met, demand more! Ask for non-hyphenated arguments!

demand_count.js:

#!/usr/bin/env node
var argv = require('yargs/yargs')(process.argv.slice(2))
    .demandCommand(2)
    .argv;
console.dir(argv);
$ ./demand_count.js a

Not enough non-option arguments: got 1, need at least 2

$ ./demand_count.js a b
{ _: [ 'a', 'b' ], '$0': 'demand_count.js' }

$ ./demand_count.js a b c
{ _: [ 'a', 'b', 'c' ], '$0': 'demand_count.js' }

EVEN MORE SHIVER ME TIMBERS!

default_singles.js:

#!/usr/bin/env node
var argv = require('yargs/yargs')(process.argv.slice(2))
    .default('x', 10)
    .default('y', 10)
    .argv
;
console.log(argv.x + argv.y);
$ ./default_singles.js -x 5
15

default_hash.js:

#!/usr/bin/env node
var argv = require('yargs/yargs')(process.argv.slice(2))
    .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:

#!/usr/bin/env node
var argv = require('yargs/yargs')(process.argv.slice(2))
    .boolean(['r','v'])
    .argv
;
console.dir([ argv.r, argv.v ]);
console.dir(argv._);
$ ./boolean_single.js -r false -v "me hearties" yo ho
[ false, true ]
[ 'me hearties', 'yo', 'ho' ]

boolean_double.js:

#!/usr/bin/env node
var argv = require('yargs/yargs')(process.argv.slice(2))
    .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, undefined, true ]
[ 'one', 'two', 'three' ]

Yargs is here to help you...

You can describe parameters for help messages and set aliases. Yargs figures out how to format a handy help string automatically.

line_count.js:

#!/usr/bin/env node
var argv = require('yargs/yargs')(process.argv.slice(2))
    .usage('Usage: $0 <command> [options]')
    .command('count', 'Count the lines in a file')
    .example('$0 count -f foo.js', 'count the lines in the given file')
    .alias('f', 'file')
    .nargs('f', 1)
    .describe('f', 'Load a file')
    .demandOption(['f'])
    .help('h')
    .alias('h', 'help')
    .epilog('copyright 2019')
    .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 
Usage: line_count.js <command> [options]

Commands:
  line_count.js count  Count the lines in a file

Options:
  --version   Show version number      [boolean]
  -f, --file  Load a file             [required]
  -h, --help  Show help                [boolean]

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

copyright 2019

Missing required argument: f

$ node line_count.js count
line_count.js count

Count the lines in a file

Options:
  --version   Show version number      [boolean]
  -f, --file  Load a file             [required]
  -h, --help  Show help                [boolean]

Missing required argument: f

$ node line_count.js count --file line_count.js
25

$ node line_count.js count -f line_count.js
25