forked from lix-project/lix-website
353 lines
8 KiB
Markdown
353 lines
8 KiB
Markdown
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# meow
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> CLI app helper
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## Features
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- Parses arguments
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- Converts flags to [camelCase](https://github.com/sindresorhus/camelcase)
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- Negates flags when using the `--no-` prefix
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- Outputs version when `--version`
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- Outputs description and supplied help text when `--help`
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- Makes unhandled rejected promises [fail hard](https://github.com/sindresorhus/hard-rejection) instead of the default silent fail
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- Sets the process title to the binary name defined in package.json
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## Install
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```
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$ npm install meow
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```
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## Usage
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```
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$ ./foo-app.js unicorns --rainbow
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```
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**CommonJS**
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```js
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#!/usr/bin/env node
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'use strict';
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const meow = require('meow');
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const foo = require('.');
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const cli = meow(`
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Usage
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$ foo <input>
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Options
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--rainbow, -r Include a rainbow
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Examples
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$ foo unicorns --rainbow
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🌈 unicorns 🌈
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`, {
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flags: {
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rainbow: {
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type: 'boolean',
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alias: 'r'
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}
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}
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});
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/*
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{
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input: ['unicorns'],
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flags: {rainbow: true},
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...
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}
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*/
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foo(cli.input[0], cli.flags);
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```
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**ES Modules**
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```js
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#!/usr/bin/env node
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import {createRequire} from 'module';
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import foo from './lib/index.js';
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const meow = createRequire(import.meta.url)('meow');
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const cli = meow(`
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Usage
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$ foo <input>
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Options
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--rainbow, -r Include a rainbow
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Examples
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$ foo unicorns --rainbow
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🌈 unicorns 🌈
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`, {
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flags: {
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rainbow: {
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type: 'boolean',
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alias: 'r'
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}
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}
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});
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/*
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{
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input: ['unicorns'],
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flags: {rainbow: true},
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...
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}
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*/
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foo(cli.input[0], cli.flags);
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```
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## API
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### meow(helpText, options?)
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### meow(options)
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Returns an `object` with:
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- `input` *(Array)* - Non-flag arguments
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- `flags` *(Object)* - Flags converted to camelCase excluding aliases
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- `unnormalizedFlags` *(Object)* - Flags converted to camelCase including aliases
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- `pkg` *(Object)* - The `package.json` object
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- `help` *(string)* - The help text used with `--help`
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- `showHelp([exitCode=2])` *(Function)* - Show the help text and exit with `exitCode`
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- `showVersion()` *(Function)* - Show the version text and exit
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#### helpText
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Type: `string`
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Shortcut for the `help` option.
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#### options
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Type: `object`
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##### flags
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Type: `object`
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Define argument flags.
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The key is the flag name in camel-case and the value is an object with any of:
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- `type`: Type of value. (Possible values: `string` `boolean` `number`)
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- `alias`: Usually used to define a short flag alias.
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- `default`: Default value when the flag is not specified.
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- `isRequired`: Determine if the flag is required. (Default: false)
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- If it's only known at runtime whether the flag is required or not, you can pass a `Function` instead of a `boolean`, which based on the given flags and other non-flag arguments, should decide if the flag is required. Two arguments are passed to the function:
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- The first argument is the **flags** object, which contains the flags converted to camel-case excluding aliases.
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- The second argument is the **input** string array, which contains the non-flag arguments.
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- The function should return a `boolean`, true if the flag is required, otherwise false.
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- `isMultiple`: Indicates a flag can be set multiple times. Values are turned into an array. (Default: false)
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- Multiple values are provided by specifying the flag multiple times, for example, `$ foo -u rainbow -u cat`. Space- or comma-separated values are [currently *not* supported](https://github.com/sindresorhus/meow/issues/164).
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Note that flags are always defined using a camel-case key (`myKey`), but will match arguments in kebab-case (`--my-key`).
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Example:
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```js
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flags: {
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unicorn: {
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type: 'string',
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alias: 'u',
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default: ['rainbow', 'cat'],
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isMultiple: true,
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isRequired: (flags, input) => {
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if (flags.otherFlag) {
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return true;
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}
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return false;
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}
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}
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}
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```
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##### description
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Type: `string | boolean`\
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Default: The package.json `"description"` property
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Description to show above the help text.
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Set it to `false` to disable it altogether.
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##### help
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Type: `string | boolean`
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The help text you want shown.
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The input is reindented and starting/ending newlines are trimmed which means you can use a [template literal](https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/template_strings) without having to care about using the correct amount of indent.
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The description will be shown above your help text automatically.
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##### version
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Type: `string | boolean`\
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Default: The package.json `"version"` property
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Set a custom version output.
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##### autoHelp
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Type: `boolean`\
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Default: `true`
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Automatically show the help text when the `--help` flag is present. Useful to set this value to `false` when a CLI manages child CLIs with their own help text.
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This option is only considered when there is only one argument in `process.argv`.
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##### autoVersion
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Type: `boolean`\
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Default: `true`
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Automatically show the version text when the `--version` flag is present. Useful to set this value to `false` when a CLI manages child CLIs with their own version text.
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This option is only considered when there is only one argument in `process.argv`.
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##### pkg
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Type: `object`\
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Default: Closest package.json upwards
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package.json as an `object`.
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*You most likely don't need this option.*
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##### argv
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Type: `string[]`\
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Default: `process.argv.slice(2)`
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Custom arguments object.
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##### inferType
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Type: `boolean`\
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Default: `false`
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Infer the argument type.
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By default, the argument `5` in `$ foo 5` becomes a string. Enabling this would infer it as a number.
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##### booleanDefault
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Type: `boolean | null | undefined`\
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Default: `false`
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Value of `boolean` flags not defined in `argv`.
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If set to `undefined`, the flags not defined in `argv` will be excluded from the result.
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The `default` value set in `boolean` flags take precedence over `booleanDefault`.
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_Note: If used in conjunction with `isMultiple`, the default flag value is set to `[]`._
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__Caution: Explicitly specifying `undefined` for `booleanDefault` has different meaning from omitting key itself.__
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Example:
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```js
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const meow = require('meow');
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const cli = meow(`
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Usage
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$ foo
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Options
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--rainbow, -r Include a rainbow
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--unicorn, -u Include a unicorn
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--no-sparkles Exclude sparkles
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Examples
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$ foo
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🌈 unicorns✨🌈
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`, {
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booleanDefault: undefined,
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flags: {
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rainbow: {
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type: 'boolean',
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default: true,
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alias: 'r'
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},
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unicorn: {
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type: 'boolean',
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default: false,
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alias: 'u'
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},
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cake: {
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type: 'boolean',
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alias: 'c'
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},
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sparkles: {
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type: 'boolean',
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default: true
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}
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}
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});
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/*
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{
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flags: {
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rainbow: true,
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unicorn: false,
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sparkles: true
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},
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unnormalizedFlags: {
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rainbow: true,
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r: true,
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unicorn: false,
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u: false,
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sparkles: true
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},
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…
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}
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*/
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```
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##### hardRejection
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Type: `boolean`\
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Default: `true`
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Whether to use [`hard-rejection`](https://github.com/sindresorhus/hard-rejection) or not. Disabling this can be useful if you need to handle `process.on('unhandledRejection')` yourself.
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#### allowUnknownFlags
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Type `boolean`\
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Default: `true`
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Whether to allow unknown flags or not.
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## Promises
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Meow will make unhandled rejected promises [fail hard](https://github.com/sindresorhus/hard-rejection) instead of the default silent fail. Meaning you don't have to manually `.catch()` promises used in your CLI.
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## Tips
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See [`chalk`](https://github.com/chalk/chalk) if you want to colorize the terminal output.
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See [`get-stdin`](https://github.com/sindresorhus/get-stdin) if you want to accept input from stdin.
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See [`conf`](https://github.com/sindresorhus/conf) if you need to persist some data.
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See [`update-notifier`](https://github.com/yeoman/update-notifier) if you want update notifications.
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[More useful CLI utilities…](https://github.com/sindresorhus/awesome-nodejs#command-line-utilities)
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---
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<div align="center">
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<b>
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<a href="https://tidelift.com/subscription/pkg/npm-meow?utm_source=npm-meow&utm_medium=referral&utm_campaign=readme">Get professional support for this package with a Tidelift subscription</a>
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</b>
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<br>
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<sub>
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Tidelift helps make open source sustainable for maintainers while giving companies<br>assurances about security, maintenance, and licensing for their dependencies.
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</sub>
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</div>
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