136 lines
4.1 KiB
Markdown
136 lines
4.1 KiB
Markdown
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# brace-expansion
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[Brace expansion](https://www.gnu.org/software/bash/manual/html_node/Brace-Expansion.html),
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as known from sh/bash, in JavaScript.
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[](https://github.com/juliangruber/brace-expansion/actions/workflows/ci.yml)
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[](https://www.npmjs.org/package/brace-expansion)
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## Example
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```js
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import { expand } from 'brace-expansion'
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expand('file-{a,b,c}.jpg')
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// => ['file-a.jpg', 'file-b.jpg', 'file-c.jpg']
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expand('-v{,,}')
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// => ['-v', '-v', '-v']
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expand('file{0..2}.jpg')
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// => ['file0.jpg', 'file1.jpg', 'file2.jpg']
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expand('file-{a..c}.jpg')
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// => ['file-a.jpg', 'file-b.jpg', 'file-c.jpg']
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expand('file{2..0}.jpg')
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// => ['file2.jpg', 'file1.jpg', 'file0.jpg']
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expand('file{0..4..2}.jpg')
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// => ['file0.jpg', 'file2.jpg', 'file4.jpg']
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expand('file-{a..e..2}.jpg')
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// => ['file-a.jpg', 'file-c.jpg', 'file-e.jpg']
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expand('file{00..10..5}.jpg')
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// => ['file00.jpg', 'file05.jpg', 'file10.jpg']
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expand('{{A..C},{a..c}}')
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// => ['A', 'B', 'C', 'a', 'b', 'c']
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expand('ppp{,config,oe{,conf}}')
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// => ['ppp', 'pppconfig', 'pppoe', 'pppoeconf']
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```
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## API
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```js
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import { expand } from 'brace-expansion'
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```
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### const expanded = expand(str, [options])
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Return an array of all possible and valid expansions of `str`. If
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none are found, `[str]` is returned.
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The `options` object can provide a `max` value to cap the number
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of expansions allowed. This is limited to `100_000` by default,
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to prevent DoS attacks.
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```js
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const expansions = expand('{1..100}'.repeat(5), {
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max: 100,
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})
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// expansions.length will be 100, not 100^5
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```
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The `options` object can also provide a `maxLength` value to cap the
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total number of characters across all expansions. This is limited to
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`4_000_000` by default, to prevent memory exhaustion from inputs whose
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result count stays under `max` while each result grows very long.
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```js
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const expansions = expand('{a,b}'.repeat(1500), {
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maxLength: 10_000,
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})
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```
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Three more options bound the work a call does rather than its output.
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Past each of them, the part of `str` that is left comes back literally
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instead of being expanded, and nothing is thrown.
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- `maxDepth` caps how deeply nested brace sets are followed. This is
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limited to `1_000` by default, to prevent stack exhaustion.
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- `maxRewrites` caps how many times Bash's `{a},b}` quirk, where a
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brace set followed by a comma set still expands, may restart the
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parse. This is limited to `1_000` by default.
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- `maxSteps` caps the total work: each character the parser scans,
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each result it builds and each sequence value it generates is one
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step, a zero-padded value is one per character, and each string it
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starts expanding, `str` itself or a member of a brace set, costs 16
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more. This is limited to `20_000_000` by default, which takes well
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under a second to spend, to prevent CPU exhaustion. Ordinary
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patterns need a few hundred steps, and nesting to the full
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`maxDepth` about 4 million. If you raise `max` or `maxLength`,
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raise this too.
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When `maxSteps` runs out partway, the top-level brace sets before the
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point where it ran out stay expanded, so the result can be partly
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expanded rather than `[str]`:
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```js
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expand('{a,b}' + '{'.repeat(10_000) + 'c,d' + '}'.repeat(10_000))
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// ['a{{{...c,d...}}}', 'b{{{...c,d...}}}']
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```
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Pass `Infinity` to lift any of these bounds.
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Valid expansions are:
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```js
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;/^(.*,)+(.+)?$/
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// {a,b,...}
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```
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A comma separated list of options, like `{a,b}` or `{a,{b,c}}` or `{,a,}`.
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```js
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;/^-?\d+\.\.-?\d+(\.\.-?\d+)?$/
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// {x..y[..incr]}
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```
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A numeric sequence from `x` to `y` inclusive, with optional increment.
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If `x` or `y` start with a leading `0`, all the numbers will be padded
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to have equal length. Negative numbers and backwards iteration work too.
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```js
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;/^-?\d+\.\.-?\d+(\.\.-?\d+)?$/
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// {x..y[..incr]}
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```
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An alphabetic sequence from `x` to `y` inclusive, with optional increment.
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`x` and `y` must be exactly one character, and if given, `incr` must be a
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number.
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For compatibility reasons, the string `${` is not eligible for brace expansion.
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