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README

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.

Yargs is the official successor to optimist. Please feel free to submit issues and pull requests. If you'd like to contribute and don't know where to start, have a look at :)

examples

With yargs, the options be just a hash!

plunder.js:

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

short.js:

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

bool.js:

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

nonopt.js:

Yargs even counts your booleans!

count.js

Tell users how to use yer options and make demands.

area.js:

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

demand_count.js:

EVEN MORE SHIVER ME TIMBERS!

default_singles.js:

default_hash.js:

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

boolean_single.js

boolean_double.js

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

methods

By itself,

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

You can pass in the process.argv yourself:

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

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, [description])

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.

But wait, there's more! the default value can be a function which returns a value. The name of the function will be used in the usage string:

Optionally, description can also be provided and will take precedence over displaying the value in the usage instructions:

.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.

.implies(x, y)

Given the key x is set, it is required that the key y is set.

implies can also accept an object specifying multiple implications.

.describe(key, desc)

Describe a key for the generated usage information.

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

.option(key, opt)

.options(key, opt)

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

For example:

is the same as

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).

.command(cmd, desc, [fn])

Document the commands exposed by your application.

use desc to provide a description for each command your application accepts (the values stored in argv._).

Optionally, you can provide a handler fn which will be executed when a given command is provided. The handler will be executed with an instance of yargs, which can be used to compose nested commands.

Here's an example of top-level and nested commands in action:

.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.

.epilogue(str)

.epilog(str)

A message to print at the end of the usage instructions, e.g.,

.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 a non-truthy value, show the thrown error, usage information, and exit.

.fail(fn)

Method to execute when a failure occurs, rather then printing the failure message.

fn is called with the failure message that would have been printed.

.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.

key will default to false, unless an default(key, undefined) is explicitly set.

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.

.string('_') will result in non-hyphenated arguments being interpreted as strings, regardless of whether they resemble numbers.

.array(key)

Tell the parser to interpret key as an array. If .array('foo') is set, --foo foo bar will be parsed as ['foo', 'bar'] rather than as 'bar'.

.nargs(key, count)

The number of arguments that should be consumed after a key. This can be a useful hint to prevent parsing ambiguity:

parses as:

{ _: [], token: '-my-token', '$0': 'node test' }

Optionally .nargs() can take an object of key/narg pairs.

.config(key)

Tells the parser that if the option specified by key is passed in, it should be interpreted 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.

By default wrap will be set to Math.min(80, windowWidth). Use .wrap(null) to specify no column limit.

yargs.wrap(yargs.terminalWidth()) can be used to maximize the width of yargs' usage instructions.

.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:

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 customizes the description of the version option in the usage string.

You can provide a function for version, rather than a string. This is useful if you want to use the version from your package.json:

.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

.showHelp(consoleLevel='error')

Print the usage data using the function consoleLevel for printing.

Example:

Or, to print the usage data to stdout instead, you can specify the use of console.log:

Later on, argv can be retrived with yargs.argv

.completion(cmd, [description], [fn]);

Enable bash-completion shortcuts for commands and options.

cmd: when present in argv._, will result in the .bashrc completion script being outputted. To enable bash completions, concat the generated script to your .bashrc, or .bash_profile.

description: provide a description in your usage instructions for the command that generates bash completion scripts.

fn, rather than relying on yargs' default completion functionlity, which shiver me timbers is pretty awesome, you can provide your own completion method.

But wait, there's more! you can provide asynchronous completions.

.showCompletionScript()

Generate a bash completion script. Users of your application can install this script in their .bashrc, and yargs will provide completion shortcuts for commands and options.

.exitProcess(enable)

By default, yargs exits the process when the user passes a help flag, uses the .version functionality or when validation fails. Calling .exitProcess(false) disables this behavior, enabling further actions after yargs have been validated.

.parse(args)

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

.reset()

Reset the argument object built up so far. This is useful for creating nested command line interfaces.

.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._.

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.

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.

dot notation

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

short numbers

Short numeric head -n5 style argument work too:

installation

With , just do:

or clone this project on github:

To run the tests with npm, just do:

inspired by

This module is loosely inspired by Perl's .

Change Log

v3.10.0 (2015/05/29 04:25 +00:00)

expose yargs.terminalWidth() thanks @ensonic (@bcoe)

README

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.

Yargs is the official successor to optimist. Please feel free to submit issues and pull requests. If you'd like to contribute and don't know where to start, have a look at :)

examples

With yargs, the options be just a hash!

plunder.js:

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

short.js:

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

bool.js:

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

nonopt.js:

Yargs even counts your booleans!

count.js

Tell users how to use yer options and make demands.

area.js:

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

demand_count.js:

EVEN MORE SHIVER ME TIMBERS!

default_singles.js:

default_hash.js:

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

boolean_single.js

boolean_double.js

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

methods

By itself,

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

You can pass in the process.argv yourself:

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

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, [description])

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.

But wait, there's more! the default value can be a function which returns a value. The name of the function will be used in the usage string:

Optionally, description can also be provided and will take precedence over displaying the value in the usage instructions:

.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.

.implies(x, y)

Given the key x is set, it is required that the key y is set.

implies can also accept an object specifying multiple implications.

.describe(key, desc)

Describe a key for the generated usage information.

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

.option(key, opt)

.options(key, opt)

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

For example:

is the same as

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

.usage(message, opts)

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

.command(cmd, desc, [fn])

Document the commands exposed by your application.

use desc to provide a description for each command your application accepts (the values stored in argv._).

Here's an example of top-level and nested commands in action:

.example(cmd, desc)

.epilogue(str)

.epilog(str)

A message to print at the end of the usage instructions, e.g.,

.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 a non-truthy value, show the thrown error, usage information, and exit.

.fail(fn)

Method to execute when a failure occurs, rather then printing the failure message.

fn is called with the failure message that would have been printed.

.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.

key will default to false, unless an default(key, undefined) is explicitly set.

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.

.string('_') will result in non-hyphenated arguments being interpreted as strings, regardless of whether they resemble numbers.

.array(key)

Tell the parser to interpret key as an array. If .array('foo') is set, --foo foo bar will be parsed as ['foo', 'bar'] rather than as 'bar'.

.nargs(key, count)

The number of arguments that should be consumed after a key. This can be a useful hint to prevent parsing ambiguity:

parses as:

{ _: [], token: '-my-token', '$0': 'node test' }

Optionally .nargs() can take an object of key/narg pairs.

.config(key)

Tells the parser that if the option specified by key is passed in, it should be interpreted 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.

By default wrap will be set to Math.min(80, windowWidth). Use .wrap(null) to specify no column limit.

yargs.wrap(yargs.terminalWidth()) can be used to maximize the width of yargs' usage instructions.

.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:

Later on, argv can be retrived with yargs.argv

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

You can provide a function for version, rather than a string. This is useful if you want to use the version from your package.json:

.showHelpOnFail(enable, [message])

line_count.js

.showHelp(consoleLevel='error')

Print the usage data using the function consoleLevel for printing.

Example:

Or, to print the usage data to stdout instead, you can specify the use of console.log:

Later on, argv can be retrived with yargs.argv

.completion(cmd, [description], [fn]);

Enable bash-completion shortcuts for commands and options.

cmd: when present in argv._, will result in the .bashrc completion script being outputted. To enable bash completions, concat the generated script to your .bashrc, or .bash_profile.

description: provide a description in your usage instructions for the command that generates bash completion scripts.

fn, rather than relying on yargs' default completion functionlity, which shiver me timbers is pretty awesome, you can provide your own completion method.

But wait, there's more! you can provide asynchronous completions.

.showCompletionScript()

Generate a bash completion script. Users of your application can install this script in their .bashrc, and yargs will provide completion shortcuts for commands and options.

.exitProcess(enable)

.parse(args)

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

.reset()

Reset the argument object built up so far. This is useful for creating nested command line interfaces.

.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._.

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.

numbers

duplicates

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

dot notation

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

short numbers

Short numeric head -n5 style argument work too:

installation

With , just do:

or clone this project on github:

To run the tests with npm, just do:

inspired by

This module is loosely inspired by Perl's .

94adee2 argv. can be told 'Hey! argv.! Don't be messing with my args.', and it WILL obey (@colinta)
c46fdd5 optimistic critter image (@substack)
5c95c73 alias options() to option() (@substack)
[fix] Fix for parsing boolean edge case (@indexzero)
[fix test] Update to ensure optimist is aware of default booleans. Associated tests included (@indexzero)
[dist test] Update devDependencies in package.json. Update test pathing to be more npm and require.paths future-proof (@indexzero)
s/sys/util/ (@substack)
update usage output (@substack)
some sage readme protips about parsing rules (@substack)
documented all the methods finally (@substack)
fenced syntax highlighting (@substack)
right-alignment of wrapped extra params (@substack)
now with .wrap() (@substack)
don't show 'Options:' when there aren't any (@substack)
failing test for multi-aliasing (@substack)
"Options:" > "options:" (@substack)
[minor] Update formatting for .showHelp() (@indexzero)
options works again, too lazy to write a proper test right now (@substack)
line_count_options example, which breaks (@substack)
line count example (@substack)
remove self.argv setting in boolean (@substack)
removed camel case for now (@substack)
remove dead longest checking code (@substack)
.help() too (@substack)
rm old help generator (@substack)
nub keys (@substack)
generate help message based on the previous calls, todo: nub (@substack)
stub out new showHelp, better checks (@substack)
let .options() take single options too (@substack)
.options() is now heaps simpler (@substack)
defaults work again, all tests pass (@substack)
update test error messages, down to 2 failing tests (@substack)
fix for bools doubling up, passes the parse test again, others fail (@substack)
refactored for an argv getter, failing several tests (@substack)
just rescan for now, alias test passes (@substack)
failing alias test (@substack)
.alias() (@substack)
[api] Remove .describe() in favor of building upon the existing .usage() API (@indexzero)
[doc api] Add .describe(), .options(), and .showHelp() methods along with example. (@indexzero)
updates for coffee since it now does argv the node way (@substack)
more general coffeescript detection (@substack)
Don't trigger the CoffeeScript hack when running under node_g. (@papandreou)
.string() but failing test (@substack)
test hex strings (@substack)
more keywords (@substack)
Added camelCase function that converts --multi-word-option to camel case (so it becomes argv.multiWordOption). (@papandreou)
fixed boolean bug by rescanning (@substack)
boolean examples (@substack)
boolean() with passing test (@substack)
coffee compatibility with node regex for versions too (@substack)
argv._ fixed by fixing the coffee detection (@substack)
whichNodeArgs test fails too (@substack)
replicated mnot's bug in whichNodeEmpty test (@substack)
test for ./bin usage (@substack)
don't coerce booleans to numbers (@substack)
package bump for automatic number conversion (@substack)
updated readme and examples with new auto-numberification goodness (@substack)
auto number conversion works yay (@substack)
failing test for not-implemented auto numification (@substack)
odd that eql doesn't check types careflly (@substack)
package author + keywords (@substack)
updated readme with .default() stuff (@substack)
passing tests for new .default() behavior (@substack)
new default() thing for setting default key/values (@substack)
test for coffee usage (@substack)
new --key value style with passing tests. NOTE: changes existing behavior (@substack)
package bump for summatix's coffee script fix (@substack)
Added support for CoffeeScript (@summatix)
test coverage for the falsy check() usage (@substack)
check bug fixed plus a handy string (@substack)
tests for demandCount, back up to 100% coverage (@substack)
call demandCount from demand (@substack)
add demandCount to check for the number of arguments in the _ list (@marshall)
Rebase checks. That will be its own module eventually. (@substack)
a $0 like in perl (@substack)
usage test hacking around process and console (@substack)
description pun (@substack)
mit/x11 license (@substack)
bool example is more consistent and also shows off short option grouping (@substack)
start of the readme and examples (@substack)
more tests for long and short captures (@substack)
silly bug in the tests with s/not/no/, all tests pass now (@substack)
hack an instance for process.argv onto Argv so the export can be called to create an instance or used for argv, which is the most common case (@substack)
divide example (@substack)
start of the lib with a package.json (@substack)

README

hashtagyargs

hashtagexamples

hashtagWith yargs, the options be just a hash!

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

hashtagAnd booleans, both long, short, and even grouped:

hashtagAnd non-hyphenated options too! Just use argv._!

hashtagYargs even counts your booleans!

hashtagTell users how to use yer options and make demands.

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

hashtagEVEN MORE SHIVER ME TIMBERS!

hashtagAnd if you really want to get all descriptive about it...

hashtagYargs is here to help you...

hashtagmethods

hashtag.alias(key, alias)

hashtag.default(key, value, [description])

hashtag.demand(key, [msg | boolean])

hashtag.require(key, [msg | boolean])

hashtag.required(key, [msg | boolean])

hashtag.requiresArg(key)

hashtag.implies(x, y)

hashtag.describe(key, desc)

hashtag.option(key, opt)

hashtag.options(key, opt)

hashtag.usage(message, opts)

hashtag.command(cmd, desc, [fn])

hashtag.example(cmd, desc)

hashtag.epilogue(str)

hashtag.epilog(str)

hashtag.check(fn)

hashtag.fail(fn)

hashtag.boolean(key)

hashtag.string(key)

hashtag.array(key)

hashtag.nargs(key, count)

hashtag.config(key)

hashtag.wrap(columns)

hashtag.strict()

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

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

hashtag.showHelpOnFail(enable, [message])

hashtag.showHelp(consoleLevel='error')

hashtag.completion(cmd, [description], [fn]);

hashtag.showCompletionScript()

hashtag.exitProcess(enable)

hashtag.parse(args)

hashtag.reset()

hashtag.argv

hashtagparsing tricks

hashtagstop parsing

hashtagnegate fields

hashtagnumbers

hashtagduplicates

hashtagdot notation

hashtagshort numbers

hashtaginstallation

hashtaginspired by

Change Log

hashtagv3.10.0 (2015/05/29 04:25 +00:00)

README

hashtagyargs

hashtagexamples

hashtagWith yargs, the options be just a hash!

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

hashtagAnd booleans, both long, short, and even grouped:

hashtagAnd non-hyphenated options too! Just use argv._!

hashtagYargs even counts your booleans!

hashtagTell users how to use yer options and make demands.

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

hashtagEVEN MORE SHIVER ME TIMBERS!

hashtagAnd if you really want to get all descriptive about it...

hashtagYargs is here to help you...

hashtagmethods

hashtag.alias(key, alias)

hashtag.default(key, value, [description])

hashtag.demand(key, [msg | boolean])

hashtag.require(key, [msg | boolean])

hashtag.required(key, [msg | boolean])

hashtag.requiresArg(key)

hashtag.implies(x, y)

yargs

examples

With yargs, the options be just a hash!

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

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

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

Yargs even counts your booleans!

Tell users how to use yer options and make demands.

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

EVEN MORE SHIVER ME TIMBERS!

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

Yargs is here to help you...

methods

.alias(key, alias)

.default(key, value, [description])

.demand(key, [msg | boolean])

.require(key, [msg | boolean])

.required(key, [msg | boolean])

.requiresArg(key)

.implies(x, y)

.describe(key, desc)

.option(key, opt)

.options(key, opt)

.usage(message, opts)

.command(cmd, desc, [fn])

.example(cmd, desc)

.epilogue(str)

.epilog(str)

.check(fn)

.fail(fn)

.boolean(key)

.string(key)

.array(key)

.nargs(key, count)

.config(key)

.wrap(columns)

.strict()

.help([option, [description]])

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

.showHelpOnFail(enable, [message])

.showHelp(consoleLevel='error')

.completion(cmd, [description], [fn]);

.showCompletionScript()

.exitProcess(enable)

.parse(args)

.reset()

.argv

parsing tricks

stop parsing

negate fields

numbers

duplicates

dot notation

short numbers

installation

inspired by

v3.10.0 (2015/05/29 04:25 +00:00)

yargs

examples

With yargs, the options be just a hash!

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

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

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

Yargs even counts your booleans!

Tell users how to use yer options and make demands.

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

EVEN MORE SHIVER ME TIMBERS!

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

Yargs is here to help you...

methods

.alias(key, alias)

.default(key, value, [description])

.demand(key, [msg | boolean])

.require(key, [msg | boolean])

.required(key, [msg | boolean])

.requiresArg(key)

.implies(x, y)

.describe(key, desc)

.option(key, opt)

.options(key, opt)